ti , :.'\ tlL

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TULAIì{E STUDIESThI GEOLOGYAIì{D

PALEOI\ITOLOGYVolume 18, Numbers 1,2 October 31, 1984

Number I

THE WALL STRUCTURE OF SUPERFAMILY MILIOLACEAANDITS LINEAGE IN THE GULF COASTALPLAIN

H. V. ANDERSEN

EVALUATION OF THE FORAMINIFERALGENERA CONG LOBAilDES AND CONG LOPHRAGMIUM

D. HAMAN and R. W.,HUDDLESTON

STATUS OF THE TORAMINIFERAL SUBGENUSMICROFASCI OLITES GAEMERS, 1978

= D. IIAMAN p.Zo

PLANKTIC FORAMINIFERA AND CALCAREOUS NANNOPLANKTONBIOSTRATIGRAPHYOF THE NEOGENE OF MEXICO

PART tr - LOWER PLIOCENE

W. H. AKERS

Number 2

NOTES ON THE GENUSAGNOCARDIA (MOLLUSCA: CARDIIDAE)WITHTHEDESCRIPTION OF A NEW SPECIESFROMTHE

PLIOCENE OF FLORIDA

HAROLDE. VOKES

A NEW SPECIES OF îURBINSLLA (MOLLUSCA:GASTROPODA)FROM THE PLIOCENE OF IUEXICO, WITH A REVISION

OF THE GEOLOGICHISTORY OFTHELINEand

THE GENUS HARPA (MOLLUSCA:GASTROPODA) IN THE NEW WORLD

EMILY H. VOKES

A REVISION OF THE TEREBRID GASTROPODSOF THE MARE FORMATION, CABO BLANCO, VENEZUELA

J. GIBSON-SMITH and W. GIBSON-SMITH

(continued on back cover)

TULAIVE UNI\TERSITY OF' LOLIISIANANeu'Orleans

p.2l

p.47

p. 3?

p- 53

Val" 18

Molus-iina deiPaleon-. 2 text

w" M"rmingo:p. 305-

,pod oc-eogene:ro. 4, p.

pidae of, D0. 16,

gR, andre of theminicanr Carib-;1-i60, 4

na iandii. Scc.,ig., 6 ta-

il " 1984

: an titi esÌes withanci re-ion pat*itafes inrractical{ versus

figures,'fìeS afeI index":rrnits acale Y

-*F{ C- S

A REVISION OF THE TEREBRID GASTROPODSo F r HE -î X;:lHi: T; î îi :,::trl,î; JiI{E

z uE LA

CARACAS. VEJ!'EZUELA

ABSTRACTThree taxa from the late Pliocene Mare

Formation, Venezuela, are considered.Strtoterebrttm trzspirolis (Weisbord, 1962)

is made a synonym of S. quadrispiralis(Weisbord, 1962) and the form assigned byWeisbord (1962) ta Terebro (Strioterebntm)gatunensis kugleri Rutsch, 1934, from theearly Pliocene Punta Gavilan Formation,Venezuela, later reassigned by WooCring(1964) to S. díslocatum (Say), is describedas a new species: S. useisbsrdi. Both S.

quadrzspiralis and S. uteisbordt survive inVenezuelan waters. Finally, a new speciesis described from the Venezuelan Recent:S. angetti.

INTRODUCTIONWeisbord (1962) cited three taxa in the

subgenus Terebro (StríaterebntznJ from thelate Pliocene Mare Formation, CaboBlanco, Venezuela. One was assigned toT. (S.) g*tunensis kugleri Rutsch, 1934,

from the early Pliocene Punta GavilanFormation, Falcón State, Venezuela. ThePunta Gavilan form, however, was laterrnade a junior synonym of S. spínferum(Dali, 1895) from the Gatun Formation,Panamé, by Woodring (1970, p. 409) who,at the same time, recognized that the Marefòrm was distinct, reassigning it to S. dis-tacatum (Say, 1822). This iast is knownfrom the early Miocene to Recent inFlorida and today ranges from Marylandto Texas, the West Indies and Brazil, butalso on the west coast from California toPanamé (Abbott 1974, p. 259; Keen 1971, p.

674). However, the Mare form, which stillsurvives in Venezuela, differs from S. dis-locatum and is described here as a newspecies : Strio terebntm uteisbordi n. sp.

*Mailing address: Quinta Puerta del Sol. CalleTucupido, San Roman, LasMercedes, Caracas 1060,

Venezuela.

The other two taxa cited by Weisbord(1962) were: T. lS.) trispiralis n. sp. and T.fs.i quadrispirolis n. sp. However, withbetter material availabie, it is ciear thatthey represent a single taxon and, al-though the former has page preference, itis referred here to S. eluadrispirculis asbeing more correctly descriptive. It alsooccurs in the Venezuelan Recent.

Lastly, a new species from the Ven-ezuelan Recent, formerly referred til S.tríspirolis and S. guodrispirsli.s by Petuch( 1981 , p. 337) is described here asStriaterebrum angelli n. sp.

It might be added that the Mare faunawas reviewed briefly by Gibson-Smith andGibson-Smith (1979, p. 24), the nurnber oftaxa still surviving in Venezuela beinggreatly increased. Two more can now beadded.

Family TEREBRIDAEGenus STRIOTEREBRUM Sacco

Striaterebntm SACCO, 1891, I Molluschi dei ter-reni terziarii de Piemonte e delia Liguria, pt.10, p. 33.

Typ* species (by original designation):T erebro basteroti Nvst.

STnToTEREBRUM wErsBoRDi

Gibson-Smith and Gibson-Smith, r. sp.Plate 1, Figures 1, 2

Terebra ( Strzoterebntm) gotunensis kuglerzRutsch, 1934. WEISBORD. 1962. Bulls.Amer. Paleontology, v. 42, no. 193, p. 428, pl,40, figs. 12, 13; pl. 45, figs,24,25. PETUCH,1981; Maiacologia, v. 20, no. 2, p. 336. figs. 99,100 (bothr nan Rutschi.

Strtoterebntm dislocotum (Say, 1822). WOOD-RING, 1970, U.S. Geol. Surv.. Prof. Paper306-D, p. 413 (under S. índoeogopum Olsson)( non S"y.)

Descriptíon: "The Cabo Blanco shell reierredto T. kuglert is of medium size, slender, the spireacuminate, the apex often siightiy bent. theangle of spire below the apex about 15 degrees.Fully gro\f,,n, the species has nearly 18 whorls in

61

62

ail, the nucleus consisting of lVz or 2 of them.Nucleus smooth, subhyaline, the tip fused andindistinct, the initial turn full, a lirtle offset fromthe last which is bulbous and larger than the firstpost-nuclear whorl, and is defined from theconch by the appearance of axial riblets. Firstpost-nuclear whorl flat-sided, sculptuSed by 14

to 18 curved axial ribs extending from suture tosuture with four or five spiral grooves in the in-terspaces. Subsequent whorls are providedwith a collar immediately below the suture thecoilar marked with subequal longitudinal rib-lets- Below the collar the sculpture consists ofrather narrow, subequal axial cords and lowerspiral ridges, the intercepts beaded, the generaipattern subreticulate. Mature shells have an av-erage of 33 axial cords on the penuitimate whorl,but there may be as many as 38 and as few as 30,one specimen having only 25. Generally thereare four spiral ridges below the collar, but hereagain the number may vary; one specimen hasbut three and several have five or six- The spac-ing of the spiral ridges is also variable. On someof the specimens the ridges are more or lessequal, on others the interspace is wider belowthe frst or second spiral ridge. On a number ofspecimens the posterior spiral ridges arestronger than the anterior, but this is not con-stant. The subsuturai collar is prominent andbroad, occupying a little over a third of thewhorl; it is crenulated by broad axial riblets orfolds about equal in number to the axial cordsbelow but larger than those. The collar isthicker posteriorily and projects slightly beyondthe preceding whorl" On later whorls, the fur-

Tulane Studies in Geology ond Paleontology Vol. 18

row below the coilar is fairly deep and wide, buton the earliest whorls, the space below the col-lar is represented by a fine groove. surfacecovered with numqrous axial growth striae- su-tttres narrowly impressed, hardly distinguish-able. Aperture sinuously lenticular. outer lipbroken back on all specimens. columeria withtwo strong folds of about the same size; thelower one forms the margin of the canai.Parietal wall with a thin covering of enamei,rather deeply excavated above the posterior ofthe columellar folds. Siphonal fascioie flattish toundulatory, built up of arched incremenrals,bordered by a strongly keeled ridge which con-tinues around to form an emargination on theside of the terminal notch. Above the keel, thebase is severely contracted into a deep broadfurrow. Last whorl with an average of 13 coarsenodulous spiral ribs of unequal size, and nearlyobsolescent axial cords, the ribs usually presentin the furrow at the base. Anterior canal short,broad, and deep, recurved backward at the ex-tremity, the siphonal notch large and broadly {.I-shaped." (Weisbord, 1962)

Addendum to descr-tption: Recent specimensare banded in brown with darker flammulesand a narrow white band below mid-whorl;nodes of subsutural collar alternating white andbrown; aperture dark brown.

Holatgpe: PRI 26324, as illustrated by Weis-bord (1962, pl. 40, figs. LZ, 13); heighr gg.3 ffiffi,diameter 9.5 mm.

Tape loealitg; Lower Mare Formation, CaboBlanco Venezuela; late Pliocene.

Puratypes: USNM 236013, NHMB H 1?0gg;BM(UfD 21461-5; Universidad Central de Ven-ezuela, UCVG 7064.

PLATE 1

FiguresL,2. Stríoterebntm ueisbordi Gibson-Smith and Gibson-Smith, D.sp.

1. Paratype, USI.IM 256013; height 48.3 mm, diameter 11.0 mm.Locality: Mare Formation, Cabo Blanco, venezuela.

2. NHMB H17098; height 38.6 mm, diameter 9.2 mm.Locality: Punta Mangle, Isla Margarita, Venezuela. Recent.

3. Strioterebnrm spinferl.tm (Dall, 1895).3. NHMB HL7100; height 49.0 hffi, diameter 11.6 mm.

Locality: Punta Gavilan Formation, Falcón State, Venezuela.4, 5. Strioterebn^nn quadr-r,spiralis (Weisbord).

4. PRI 8228; heightz4.8 mm, diameter 5.5 mm.Locality: Mare Formation, Cabo Blanco, venezuela.

5. NHMB H17101; height 16.2 mm, diameter 3.7 mm.Locality: Recent, Punta Moron, Carabobo State, Venezuela.

6,7 . Strioterebntm ongelli Gibson-Smith and Gibson-Smith, o.sp.6. Holotype, {JSNM 78472a; height 15.4 mm, diameter 4. I mm.7. Same, whitened.

(All illustrations magnified x 7)

Voi. ì I

rrci u'ide, but,iuu' tire r:oì-r!'É, . Surf';rt:t,,it síri;re. Sir-distinguisli-r. Otiter iipiurnell;i withrle size; the

th e canaì.of'enamel,posterior of

"rle flattish {.o

r{:rementals,: which con-Ition on thehe keel, thedeep"r broadof tr3 cCIarse

. and nearlvraliy presentcanal short,rd at the ex-J broadiy'U-

t spiecimens' flammulesmid-whorl;

g white and

'd by Weis-ht 38.3 mm.

ation. Cabo

B H 17098;rai cle Ven-

i{o" 2 T erebriC Ga..s tru^rtods

PLATE 1

63

64 Tulane Studies in Gealogg and Paleontologg Vol. 18

Range: Also Recent along the north coast of StrzotercInam baodenensis Woodring, 1928.Venezuela from the Golfo de Venezuela to Isla PETUCH, 1991, Malacologia, v. 20, no. 2, p.Margarita. 36, fig. 98 lnoa Woodring).

No. 2

terta (Conrscription ojwhorls arehott, 1974, rashy to iarThe ances:lieved to b,from the i

Forrnation,coarsely scaxial ribs, a

S,

Gibson-S,

Str-toterebnnPETUCF{337, figs" '!

Súrioter ebrtrnPETUCH337, figs. I

? StrtoterebruPETUCH336, figs. 1

Descriptiorthe genus, rtoconch of (

whorls; ten s

about the micsuture. A strmited by a nreduced axi:opisthocyrt, r

terspaces. T'more on theover the midrthe axial ribsscopic, crowfold. Colour a

ashy band abtbe subsuturrribs also sorrrrinside of aper

Holotype: L

ameter 4.2 mtType loca|

Margarita, VrParatypes.' .

17099: Univeucvc 7065.

Remarks:of Strtoterenumber of r700 eame I

Punta Manpalso on a m'

Remorles: There are 435 specimens avail-able in the collections of the authors. Asingle, worn specimen was recorded byWeisbord (Ioc. cit.) from the MaiquetiaMember, Playa Grande Formation, atPunta Gorda (locality W-23 _ GS-?-CB).However, as stated by Gibson-Smith andGibson-Srnith (1979, p. 21) this locality alsopertains to the Mare Formation. The Re-cent suite consists of 26 specimens foundmainly in beach drift, but also at depthsdown to 15 meters. For comparison thereare 54 topotypes of S. spinferurrl fromPunta Gavilan and 37 specimens of ,S. dis-Ioeatum from Florida.

C amparisons : S triaterebrum us e ísbordi n.sp. differs from S, spínferurn (FiS. 3) inbeing more tightly coiled in the adult, withlower whorls; the spiral groove below thesubsutural cord is wider and across it theaxial ribs are obsolescent. The columellarfold in S. useisbordí is strongly bipartite;whereas, in S. spirder"trna it is broad andlow, possibly representing two cornpletelyfused folds. The base of the whorl in S.uteisbordi is more abruptly constricted, r€-sulting in a shorter more sharply recurved,anterior canal. Finally, S. uteisbordi issmaller than S. spinfenLrn, reaching aheight of 65 Dersus 95 mm. Weisbord (Ioc.cit.) noted a similarity between S. useis-bordi and S. díslocatum, but found that"the Cabo Blanco shells have a greaternumber of axial cords, the groove belowthe subsutural collar is more pronouncedand the two columellar folds are not fusedas they are on T. dislocata." It can beadded that in S. díslocatum the subsuturalcollar is wider, occupying more of thewhorl height, and, the attendant, narrowergroove is crossed by the reduced axial ribs.

SrnlorEREB RUM euADRrs prRALrs WeisbordPlate 1, Figures 4, 5

Terebra (Stnoterebntm) quadrùspirulis WEIS-BORD, 1962, Bulls. Amer. Paleontology v.42, no. 193, p. 431, pl. 41, tìgs. 1-4.

T e r e br o ( S tn oter ebntm ) trl" spiral i s WE I S B O R D,1362, Bulls. Amer. Paleontology, v. 42, no.193, p.430, pl.40, fìgs. 14, 15.

NOT Strtoterebntm qrndnspiralis Weisbord.PETUCH, 1981, Malacologia, v. 20, no. 2, p.337, figt. 103, 104 ( S. angelli n"sp.).

IYOT Strzoterebntm trt.spíralís Weisbord,PETUCH, 1981, Malacologia, v. ZA, no. 2, p.337, figs. 105, 106 ( * S. angelli n.sp.).

Ad.d.endum. to deserip tisn: Shell reaching aheight of 26.4 mm with a diameter of 6.6 mm.Protoconch of one and one-fourth whorls, tele-oconch of 11 to LZ whorls. Number of spiraicords varying between three and eight" In Re-cent specimens the shell is orange-brown in col-our with a iighter band at the rniddle of thewhorl, many specimens having faded (?) towhite.

Rernorlcs; With a suite of 61 Mare speci-mens available it is clear that S. trispiralisand S. quodnspiralis are the same. Of 41adult specimens, three have three spiralcords, L7 have four and 2L have five toeight spiral cords. They are referred to S.qualnspiralis as being more representa-tive of this taxon, rather than to S. úrús-piralís which has page preference. A Re-cent suite of 118 specimens comes from tenlocalities along the north coast of Ven-ezuela between Adicora, ParaguanéPeninsula, and Punta Mangle, Isla Mar-garita; most came from beach drift, butsome are from a depth of 55 meters in aseafloor sample from a Maraven S.A. dril-ling location in the Ensenada de Barcelona(Well EBC-l-X; coordinates: N.10" 18' 28",W.65" 32' 00'J. The Recent form is some-what smaller than the fossil, maximumheights being 22.3 and 26.4 mm withmaximum diameters of 4.8 and 6.6 rnm, F€-spectively; in both there is a variation inthe degree of stoutness. Two Recent speci-mens from the Golfo Triste, Venezuela,were assigned by Petuch (1981, p. 336, fig.98) to S. bou;denensis (Woodring, 1928)from the early Fleistocene Bowden For-mation, Jamaica; they are specimens of S.quadnspiralis. The protoconch of S. bout-denensís is of two to two and one-halfwhorls and the diameter of a large shellquoted by Woodring (1928, p. 138) is L2.2mm at a broken height of 28. I mm. indicat-ing a very much larger shell than is S.quadnspirclis. The homologue of S. quú-rtspiralis in Florida seems to be S. pro-

No. 2 Tereffi,d Gastropods

terta (Conrad, 1845); we have found no de-scription of its protoconch, but the spirewhorls are said to be stightly concavu (Ab-bott, 1974, p. 260) and its purplish-black, otr

ashy to dark purple, colour is also distinct.The ancestor of S. quadrtspirolis is be-lieved to be S. nl,eesrnanni (Rutsch, 1934)

from the early Pliocene Punta GavilanFormation, Falcón State, but that is morecoarsely sculptured, with heavily beadedaxial ribs, as seen in 15 toPotYpes.

Stnto'rE REB RI'M AIIGET'r'T

Gibson-Smith and Gibson-Smith, h. sP'

Plate 1, Figures 6, 7.

Stnoterebntm quadríspíralís (Weisbord, 1962).

PETUCH, 1981, Malacologia, v- 20, no' 2, p'33?, fig=. 103, 104 (non Weisbord)-

strzoterebntrn tríspíralis (weisbord, 1962).

PETUCH, 1981, Malacologia, v- 20, no' 2, p'33?, figs. 105, 106 (non Weisbord)-

?Striote rebntm isch"na (Woodring, 1928)'

PETUCH, 1981, Malacoiogia, v- 2A, no' 2, p'336, figs. 101, 102.

Descrip tion: Shell small, somewhat stubby forthe genus, reaching a height of 15 mm' Pro-toconch of one and one-half smooth, brownwhorls; ten sculptured whorls. whorls bulgingabout the middle, the periphery close to anteriorsuture. A strongly noded subsutural cord deli-mited by a narrow, deep sulcus crossed by thereduced axial ribs. Axial ribs strong, sharp,

opisthocyrt, numberi.tg 13 to 15 with wider in-terspaces. Two to five flat spiral cords, withmore on the base, often weak to obsolescent

over the middle of the whorl and failing to node

the axial ribs. shell surface covered in micro-scopic, crowded spiral striae. No columellarfold. colour a dark purplish brown with a lighter

ashy band about the whori middle; the nodes ofthe subsutural collar and the crests of the axialribs also sometimes ashy. columella brown and

inside of aperture a translucent brown'Holotypà; USNM 784720; height 15'4 mm, di-

ameter 4.2 mm.TUpe locality: Recent, Punta Mangle, Isla

Marlarita, Venezuela.Paratypes: AMNH 202289: BM(NH); NHMB H

17099: IJniversidad central de venezuela,UCVG 7065.

Remarks: There are some 900 paratypes

of Strtoterebntm angel|í n'sp'from a

number of north coast localities. of these,

?00 came from suction-dredge spoil at

Punta Mangle, Isla Margarita; they occuralso on a mud flat with Tholassio at adja-

65

cent Punta de Piedras. None were reco-vered in the carbonate province of theoffshore islands; they prefer, seemingly, amuddier environment. The name recordsour appreciation of much help, includingdonation of materiàI, given by marinebiologist Charles Angell, at one time incharge of oyster and shrimp culture at theEstación de Investigaciones Marinas,Punta de Piedras, Isla Margarita.

Comporisorus: Although assi$ned byPetuch (1981, p. 337), using our material, toS. trispírolis Weisbord and S. quadrís-piralts Weisbord (redefined earlier as onespecies under S. quadr-tsptralis), S. angelliis not closely related and is little over halfthe size. Nor do there seem to be any otherclosely related Recent taxa. Its ancestormay be Strioterebrttm brechincastrensís(Rutsch, L942) from the eariy PlioceneSpringvale Formation, Trinidad; it has

similar bulging whorls and strong, opis-thocyrt axial ribs, but it is twice the size ofS. angelli, reaching a height of alrnost 30

mm. An undescribed form related to S.

brechincastrensis is present in the earlyPliocene Punta Gavilan Formation' Thestatus of the form assigned by Petuch(1981, pp. 336, 337) to Stri oterebntm isclt'na(Woodring, 1928) from the early Pleis-tocene Bowden Formation, Jamaica, is

problematical; it occurs together with S.

angellí at Adicora, Paraguané Peninsula;with its bulging whorls and strong opis-thocyrt axials, it has much the appearanceof that species. S" ischna on the other handis smaller and slimmer, its whorls less con-vex and it virtually lacks a subsutural cord,giving to some specimens a Hastulo-likeappearance (Woodring, 1928, p. 136). Thisform from Adicora may be no more thanjuvenile S. angellí.

LITERATURE CITEDABBOTT, R. T., 19?4, American Seashells, 2nd

Edition. Van Nostrand Reinhold Co., NewYork, 663 p., 4000 * text figs., 24 col. pls.

GIBSON-SMITH, J. and W. GIBSON-SMITH'19?9, The genus Arcinella (Mollusca:Bival-via) in Venezuela and some associatedfaunas: GEOS, no. 24, p- 1l-32, 3 pls., 2 textfigs.

KEEN, A. M., 19?1, Sea shells of tropical WestAmerica; marine mollusks from Baja Califor-nia to Peru, Znd Edition- Stanford Univ.

66

Press" Stanford, Calif. i-xiv + 1064 p., ca.

4000 text figs., 22 col. pls.PETUCH, E. J., 1981, A relict l{eogene

caenogastropod fauna from northern SouthAmerica: Malacologia, v. 2A, no. 2, p. 307-

347. 130 figs.WEISBORD, N. 8., 1962, Late Cenozoic gas-

tropods from northern Venezuela: Bulls.Amer. Paleont., v. 42, no. 193, 672 p", 48 pls.

WOODRING, W. P., 1928. Miocene mollusks

Tu\ane Studíes in Geology and Paleontologg Vol. 18

from Bowden, Jamaica; Carnegie Inst. t REÌWashington, Publ. 385, 564 p., 40 pls.

WOODRING, lV. P., 1970, Geology and paleon-tology of Canal Zone and adjoining parts ofPanama. Description oi Tertiary mo.llusks(Gastropods: Eulimidae, il{arginellidae toHelminthoglyptidae): U. S. Geol. Surv.,Prof. Paper 306-D, p. 299-+52, pis. {8-66.

October 31, 1984 The late (tigata is shovopisthogyratestances, a prCI

dial ribs or stported from G

to Mississippi r

The name .f

ner (1916, p. :

of GlycAmerisment was behhence the nasumed that t

(prosogyrate).for the orienteare what onpelecypods. F

Postligata. isthought, it w(pare this genlglycymerididsmost other piPostligata an(rectly, but mi426) haveglycymerididson both anatctics.

The followirthe shell arethe valves of g

1. The scarmuscle is subtmore angular.of the posterwhich is subcir

IìEVIEW

DISTRIBUTION OF SHALLOW-WATERMARII\iE MOLLUSCA, YUCATA}IPEI{INSULA, MEXICO, by Harold E.Vokes, and Emily H. Vokes. Pubiishedby Middle American Research Instituteand Mesoamerican Ecology Institute ofTulane lJniversity, New Orleans, 1983,viii + 183 pp., illus., atlas of 50 pls.,paper $21.50 (including postage and han-dling)This monograph presents the data com-

piled during the past twenty-five years bythe late E. Wyllys Andrews IV and byHarold and Emily Vokes, who joined himin this project in 1964. When Dr. Andrewsbecame ill and it became apparent that hewould not survive, the doctors Vokespromised him that they would see theircombined efforts through to completion.This handsomely illustrated volume re-cording 769 identified species from 99localities and their distribution withinseven ecological provinces along the coastsof Yucatan amply fulfills their promise.The book is dedicated to Bill Andrews.

Yucatar, a quadrangular limestone plat-form, occupies an unique position geog-raphicaily and ecologically. Its easternmargin fronts on the Caribbean Sea anddrops steeply into deep waters; its north-ern and western margins are on the Gulf ofMexico and have broader and shoalershelf areas known as the Yucatan Bank.

Further, the eastern margin is borderedby a neariy continuous series of coral bar-rier reefs, but coral gror,vth is confined tothe outer reaches of the Yucatan Bank andconsists of relatively small patch reefs. Thewaters off the east coast are deep blue andmud-free, those off the northern and west-ern coasts are milky green reflecting therather high content of suspended "lime-mud" sediments. These physical differ-ences contribute to the striking differencesin the faunas and ecological environmentsof the eastern coast compared with thenorthern and western coasts. These, andother geological, geographical, and ecolog-ical features are described and explaineCin the text. This monograph is an ex-tremely important contribution to theknowledge of Recent molluscan distribu-tions and ecology and is highly recom-mended to all readers interested in thisfield of study.

The volume is number 54 of the prestigi-ous Publications series of the MiddleAmerican Research Institute. It also com-prises Monograph 1 of MesoamericanEcology Institute, a new series. Both insti-tutes were among those institutions whosupported the research recorded therein.Publication 54 may be ordered from theMiddle American Research Institute,Tulane University, New Orleans,Louisiana 70118 USA.

--HCS

*Mailing addres