CONCHOLOGIST VOLUME XXXVIII, No. 1 ISSN 0885-1263 SEPTEMBER, 2001 The Texas Conchologist is the official publication of the Houston Conchology — Society, Inc., andis published occasionally at Houston, Texas. Itis distributed as — part of the dues to all its members. The Society holds regular meetings the fourth Wednesday in each of the follow- ing months: August, September, October, January, February, March, April, and May. In November, the meeting is held the third Wednesday. An annual auction is held in place of the March or April Meeting Meetings are held at Southside Place Club House, 3743 Garnet, Houston, Texas. Meetings begin at 8:00 p. m. The Texas Conchologist is published December, and June. It is mailed post- paid to regular members in U.S. postal zones. Overseas members will be charged additional postage. Only one copy will be mailed to a family mem- bership. Dues extend from the beginning of the fiscal year of June 1 through May 31. However, the May issue of the Texas Conchologist each year is the second issue due on the regular dues year beginning June 1 of the previous year. Member- ships will be accepted throughout the year but will receive issues of that fiscal year. Members receive meeting Newsletters and have all other privileges pro- vided by the Society's by-laws. Rates and Dues Family membership $12.00 Single Membership $10.00 Student membership $ 6.00 Single issues $ 2:50 Extra sets mailed to members $10.00 (Postage for overseas members required) Subscription $12.00 (Seamail $5.00, Airmail outside U.S. $8.00) Co- Editor Editorial Advisor Darwin G. Alder Dr. Helmer Odé 4250 W. 34th St. #103 3319 Big Bend Dr. Houston, TX 77092 Austin, TX 78731 (713) 682-6258 (512) 452-7799 Scientific Advisor/Co-Editor Dr. John Wise Houston Museum of Natural Science Houston, TX 77030 (713) 639-4677 The Texas Conchologist accepts contributions for publication from amateurs, students, and professionals, subject to approval by the Editors. Manuscripts should be typed and double spaced, and should be in the hands of the Editors the first day of the month preceding publication dates. Photos accompanying articles are welcomed. TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Fisurella rosea in Texas Roe Davenport, Jr. Fisurella rosea (Gmelin, 1791) is considered to be a Carib- bean species, found from southern Florida to the West Indies & Brazil (Abbott, 1974, Rehder, 1981). Therefore, it was a surprise to find two of these limpets on a single rock at South Padre Island in December 2000. A review of literature for the Gulf of Mexico shows no record of this species. (Odé, 1974- 1995, Keeler, 1994, Shelton, 1994, Tunnell et al, 1978, Vega et al, 1984). The only species of Fissurella listed for this area is F. barbadensis (Gmelin, 1791), which has been found in Vera Cruz, Mexico (Vega et al, 1984). Vokes and Vokes (1983) show Fissurellid species in the Caribbean off Yucatan, Mexico, but not occurring in the Gulf of Mexico. It is possible these snails arrived at this location in the ballast water of a ship. References: Abbott, R. T., American Seashells, 2nd Edition, Van Nostrand Reinhold, 1974. Keeler, J. H., From The Big Bend to the St. Joe: A Survey of the Marine Mollusks of the Northeastern Gulf of Mexico, pre- sented at 1994 A.M.U. Annual Meeting, Houston, Texas. Odé, H., Distribution and Reords of ther Marine Mollusca in the Northwest Gulf of Mexico, Texas Conchologist, Sept. 1974 thru Oct. 1995. Rehder, H. A., The Audubon Society Field Guide to North American Seashells, Knopf, 1981. Shelton, D. M., A Systematic Listing of Mollusks in the Northern Gulf of Mexico off the coast of Alabama, presented 1994 A. M. U. Annual Meeting, Houston, Texas. Tunnell, J. W. Jr., J. C. Woods, M. K. Linndinger and J. L. Kindinger, Fauna of the Shelf-Edge Banks in the Northwestern Gulf of Mexico, Corpus Christi State Univ., May, 1978. Vega, M.E., J. E. Gourley, and J. W. Tunnell, Jr., A Preliminary 1 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Checklist of Selected Groups of Marine Organisms Inhabiting Southwestern Gulf of Mexico Coral Reefs, Corpus Christi State University, May, 1984. Vokes, H. E. and E. H. Vokes, Distribution of Shallow-water Marine Mollusca, Yucatan Peninsula, Mexico, Pub. No. 54, Middle American Research Institute, Tulane University, 1983. South Padre Island, Texas A List of Live Collected Mollusks from the Coast Guard Station Tidal Flats Roe Davenport, Jr. It has been known for years one of the most productive places to find molluscan species (on the Texas coast) are the flats south of the Coast Guard Station at South Padre Island. This, in part, is due to the fact it is the southern end of Texas, with more tropi- cal species than other parts of the coast. Also there are a variety of habitats here, including rocks, large patches of sand, and large areas containing different species of grasses. The latter, com- prised mostly of Halodule wrightii (Shoal Grass) also includes patches of Thalassia testudinum (Turtle Grass) , as well as nu- merous species of algae. Additional habitat is provided by clumps of oysters Crassostraea virginica. The following is a list of the live molluscan species | have col- lected or observed (in parentheses) in this area, from Decem- ber, 1992 until present. Also included are various of the habitats where each species have been found. GASTROPODA: Fissurellidae Diodora cayenensis rocks Lucapinella limatula rocks Tricoliidae Tricolia sp. (not cruenta) grass, rocks Neritidae Nerita fulgurans rocks Neritina virginea grass Smaragdia viridis (viridemaris) grass 2. TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Littorinidae (Littorina anguilifera) Littorina lineolata Littorina meleagris Littorina nebulosa Caecidae Caecum pulchellum Fartulum ryssotitum Cerithidiidae Cerithium lutosum Cerithium sp. Diastomatidae Diastoma varium Cerithiopsidae Cerithiopsis sp. Selia adamsi Litiopidae Alaba incierta Triphoridae Triphora_ nigrocincta Epitonidae Epitonium apiculatum Melanellidae Balcis jamaicensis Melanella arcuata Polygireulima (Melanella) conoidea Crepidulidae Crepidula convexa Crepidula plana Ovulidae Cyphoma macgintyi Simnialena uniplicata Naticidae Natica pusilla Polinices duplicatus Sinum perspectivum Tonnidae (Tonna galea) Turridae Crassispira monilia Kurtziella limonitella Pyrgocythara coxi (?) Pyrgocythara plicosa Terebridae Hastula maryleeae Buccinidae Pisania tincta rocks rocks rocks rocks rocks rocks grass/sand rocks grass rocks grass, rocks grass rocks rocks grass/sand rocks grass/shell grit shells shells sea-whip coral sea-whip coral sand sand sand grass, sand shell grit sand sand/grass grass, shell grit sand rocks TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Columbellidae Anachis floridana Anachis sp. (=semiplicata auct.) Anachis sparsa Anachis obesa Anachis ostreicola Muricidae Morula nodulosa Thais haemastoma floridana Thais rustica Nasseriidae Nassarius acutus Nassarius albus Nassarius vibex Fasciolariidae Fasciolaria lilium Pleuroploca gigantea Melongenidae Busycon perversum pulleyi Olividae Olivella dealbata Olivella minuta Acteonidae Acteon punctostriatus Bullidae Bulla striata Scaphandridae Acteocina canaliculata Acteocina candei Hamineidae Haminoea antillarum Haminoea succinea Pyramidellidae Pyramidella crenulata Boonea impressa Turbonilla crenulata Turbonilla sp. Houbricka interrupta Houbricka textilis Houbricka sp. Aplysidae (Aplysia brasiliana) (Aplysia dactylomela) (Aplysia sp. may be donca) (Aplysia willcoxi) (Aplysia willcoxi fma perviridis) 4 rocks grass, rocks rocks grass, rocks grass, shells rocks rocks rocks sand rocks, shell grit grass/sand rocks rocks grass/sand sand sand sand sand, rocks sand/grass sand/grass sand, grass sand, rocks grass/sand oysters rocks rocks sand, grass rocks grass/sand grass among rocks grass grass grass TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Notarchidae (Bursatella leachi plei) Spurillidae (Spurilla neapolitana) Cadlinidae (Cadlina sp.) BIVALVIA Nuculanidae Nuculana acuta Arcidae Arca imbricata Barbatia candida Barbatia domingensis Anadara transversa Lunarca ovalis Noetiidae Noetia ponderosa Arcopsis adamsi Mytilidae Brachiodontes domingensis Brachiodontes exustus Musculus lateralis Lithophaga aristata Pinnidae Atrina seminuda lsognomonidae Isognomon alatus Isognomon bicolor Pectinidae Aequipecten muscosus Argopecten gibbus Argopecten irradians amplicostatus Anomiidae Anomia simplex Limidae sp. (= pellucida auct.) Ostreidae (Crassostrea virginica) Ostreola equestris Lucinidae Linga amiantus Crassatellidae Crassinella lunulata Chamidae Chama congregata grass shell rocks sand rocks rocks rocks grass/sand, rocks, shell rocks grass/sand rocks shell rocks, shell rocks rocks sand/grass rocks, oysters rocks sand/grass shell grit grass grass rocks rocks, sand shell shell grit shell grit rocks TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Cardiidae Trachycardium muricatum Laevicardium mortoni Laevicardium pictum Laevicardium robustum Mactridae Mactra fragilis Mulinia lateralis Spisula solidissima similis Tellinidae Tellina iris Tellina tampaensis Tellina versicolor Tellina cristata Semelidae Semele bellastriata Semele proficua Semele purpurascens Abra aequalis Psammobiidae Tagelus divisus Veneridae Gouldia cerina Chione cancellata Chione intapurpurea Timoclea grus Mercenaria campechiensis texana Petricolidae Petricola typica Corbulidae Corbula contracta Corbula dietziana Corbula swiftiana Hiatellidae Sphenia antillensis Lyonsiidae Lyonsia hyalina floridana POLYPLACAPHORA Ischnochiton papillosus Chaetopluera apiculata unknown family chiton (tan) chiton (white w/brown) chiton (dark) grass, shell grit sand/grass grass/shell grit sand sand/grass sand sand sand sand shell grit, sand shell grit shell grit shell grit, sand/grass shell grit shell grit, sand sand/grass shell grit sand/grass sand rocks sand/grass sand/grass sand rocks shell grit shell grit, sand shell grit, sand rocks rocks shell, rocks shell shell shell shell TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Ecological Distribution of Shallow-Water Mollusca on Alacran Reef, Campeche Bank, Yucatan, Mexico. David W. Hicks, Noe C. Barrera, and John W. Tunnell, Jr. Center for Coastal Studies Texas A&M University-Corpus Christi 6300 Ocean Drive, Corpus Christi, Texas 78412 Keywords: molluscan ecology, micromollusks, coral-reef mollusks, Gulf of Mexico, mollusk survey Abstract: The distribution of Mollusks at Alacran Reef, Mexico, was investigated in January and July 1986. Alacran Reef, a coral atoll, is the largest and most northerly in a chain of coral reefs on the Campeche Bank, a sub- merged, northward extension of the Yucatan Peninsula. The reef com- plex was divided into 8 habitat types from which 18 sampling stations were established. Mollusks were collected from each habitat type by snorkeling, SCUBA, or wading. Sediment samples were collected from selected habitats and examined for micromollusks. In additon, beach shells were collected from the sand cays (Desterrada, Desertora, Perez, Chica, and Pajaros) on the leeward edge of the reef. A total of 215 species representing 77 families and 139 genera (151 gastropods, 63 bivalves, and 1 chiton) were collected. Rice and Kornicker (1962, 1965) reported 104 gastropods and 42 bivalves from this area. of which, 61% and 79% were collected during our study respectively. The combined efforts of Rice and Komicker (1962, 1965) and the present study bring the total number of mollusks inhabiting Alacran Reef to 265 species. Previously, Strombus gigas were reported occurring at 1-2 individuals - 0.83 m? near Isla Perez. However, our survey indicated greatly reduced numbers of conchs in this area. Over-fishing of these snails could lead to their extirpation from Alacran Introduction: Campeche Bank, a large (103,600 km), northward submarine extension of the Yucatan Peninsula supports a myriad of coral reefs. Arcas (20° 13’ N, 91°58’W), Triangulos (20° 58’N, 92°18' W), Arenas (22°07’N, 91°, 24’W), and Alacran (22°23’ 36" N, 89°41’45" W), are the more important and well known of these tropical reefs (Chavez et a/.,1985). Alacran, the largest (26 X 13 km) and northeasternmost reef, lying approximately 135 7 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 km north of Progreso, Yucatan, Mexico, is the only coral atoll of the Campeche Bank (Fig. 1) (Hildebrand et al., 1964). Alacran reef was first described as a coral atoll by Alexander Agassiz (1878-1879) while on board the U.S. Coast and Geodetic Survey Steamer “Blake.” Typical of coral atolls, Alacran consists of windward and leeward reefs separated by a central lagoon (23 m deep in its southern portion; Chavez et al., 1985). Alacran, Spanish for scorpion, presumably reflects the contours of the reef (Hoskin, 1963), however it has been described as elliptical (Folk and Robles, 1964; Hoskin, 1963). Alacran's emergent platform reef covers an area of 260 km? (Kornicker and Boyd, 1962a). Winds, waves, and sea surface currents at Alacran are predominantly from the east (Hoskin, 1966; Folk and Cotera, 1971). Sea surface temperatures near Alacan range from 28.9°C in August to 23.9°C in February (Hoskin, 1966). The windward side of the Alacran Reef is virtually a smooth con- tinuous semi-circle with no permanent islands (Folk and Robles, 1964). In contrast, the irregularly shaped leeward edge accommodates a series of sand cays. The cays from north to south are Desterrada (formerly East and Westislands), Desaparecida (not present in 1986), Desertora [may also called Isla Muerta (Hoskin, 1963)], Perez, Chica, and Pajaros (Fig. 1). The sand cays are sparsely vegetated with grasses, low-lying scrubs, and succulent herbs including seashore dropseed (Sporobolus virginicus), sea purslane (Sesuvium portulacastrum) and West Indian sea Lavender (Tournefortia gnaphalodes)R. (Millspaugh, 1916; Bonet and Rzedowski, 1962). The largest of these cays, Isla Perez (870 m long, 150-180 m wide), has a sizable stand of Australian pines (Casuarina sp.). The cays of Alacran Reef provide nesting habitat for many birds, including Masked Booby (Sula dactylatra), Red-footed Booby (Sula sula), and Magnificent Frigate bird (Fregata magnificens)(Folk and Robles, 1964; Tunnell and Chapman, 1988). Important fisheries In order of decreasing production) resources obtained from Alacran are, in order of decreasing production, are red snapper (Lutjanus campechanus), green turtle (Chelonia mydas mydas), barracuda (Sphyraena barracuda), spiny lobster(Panulirus argus) and queen conch (Strombus gigas) (see Hoskin, 1963). Although Alacran is considered to be the best known of the Mexican coral reefs (Fosberg, 1961; Chavez et a/., 1985), a majority of our knowl- edge is geological and paleoecological in nature (Kornicker et al., 1959; Komicker and Boyd, 1962a,b; Wright and Komicker, 1962; Hayes, 1962; Hoskin, 1963; Davis, 1964; Folk and Robles, 1964; Gonzalez, 1965; Bonet, 1967; Folk, 1967; Folk and Cotera, 1971; and Macintyre, 1977). Few papers have dealt specifically with its living resources (Millspaugh, 8 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 1916; Kennedy, 1917; Bonet and Rzedowski, 1962; Fosberg, 1962; Hildebrand et al., 1964; Boswall, 1978; Tunnell and Chapman, 1988), and only one paper has dealt specifically with mollusks Rice and Komicker (1962, 1965), while two regional molluscan studies included data from included data from Alacran (Boudreaux 1987 and Gonzalez et al., 1991). The purpose of this study is to report the diversity and distribution of the marine mollusks fauna within the different habitats at Alacran Reef, Mexico. Materials and Methods: The distribution of mollusks at Alacran Reef, Mexico, was investigated during January and July 1986. The majority of sampling was conducted in the vicinity of Isla Perez, located in the southwestern part of Alacran near the leeward reef (Fig. 1). The locations of sampling areas are shown in figures 1 and 2. Macromollusks were collected from various habitat types, the major of which included reef slope, reef flat, mixed Thalassia and coral, and seagrass beds. Other habitats immediately surrounding the sand cays included the, rocky intertidal, intertidal moats, coral rubble and unvegetated carbonate sands. In addition, beach shells collected from the shores of Desterrada, Desertora, Perez, Chica, and Pajaros. Within each reef habitat type, mollusks were collected by wading, snorkeling, and SCUBA. Molluscs were preserved in 10% formalin, transferred to 45% isopropanol and identified to species. Micromolluks (< 10 mm) were obtained from 250-300 ml sediment samples taken by hand from the: 1) southwest reef slope near Isla Perez (Stations 1, Fig. 2); 2) reef cut (Station 16, Fig. 2); 3) the windward reef flat near the “Boiler” wreck (Fig. 1); 4) patch reef in the lagoon (Station 14, Fig. 2); 5) turtlegrass bed at Isla Perez (station 11, Fig 20; 6) beach at Isla Desterrada (Fig. 1). Sediment samples were dried, and the total volume of each sample was measured in a graduated cylinder. These samples were mixed in a pan until homogeneous, divided into 50-ml subsamples, and sorted using a dissecting microscope. Micromollusks were placed into the 3mm-wells of micropaleontological slides, identi- fied and labeled. Cumulative species area curves were generated to determine the number of 50-ml subsamples required to adequately rep- resent each habitat type. TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 A qualitative measure of abundance was assigned to species (including beach shells) collected in each habitat type. Abundance categories were assigned as follows: abundant = >50, common = 6-50, uncommon = 2- 5, and rare = 1. Species lists were compiled following Vaught (1989) and specimens were deposited at Texas A&M University-Corpus Christi. Results and discussion: A total of 215 species of mollusks were collected from Alacran Reef area. The 215 species represent 77 families and 139 genera, and con- sist of 151 gastropods, 63 bivalves, and | chiton. The most abundant families of gastropods were Caecidae (10 species), Marginellidae (9 spe- cies), Turbinidae (9 species), Fissurellidae (8 species), Rissoidae (7 species), and Buccinidae (6 species). The Tellinidae (8 species), Arcidae (7 species), Mytilidae (5 species), Lucinidae (5 species), and Chamidae (5 species) were the most abundant bivalve families. Members of the genera Lithopoma, Cerithium, Engina, Pollia, and Columbella were the most ubiquitous gastropods, while Barbatia spp. and Glycymeris spp. were the most widespread bivalves. The localities of sampling stations are shown in figures 1 and 2 with abundance and habitat notations for each species presented in Table 1. The reef slope (Station 1, Fig. 2) south of Isla Perez is marked at the base by distinctive groove and spur development and sparsely boulder coral (Monastrea annularis). Coral heads of yellow porous coral (Porites astreoides, 20-25 cm diam.) were interspersed along the upper portion reef slope and above the groove and spur zone. Nine species of gastro- pods and three species of bivalves were collected from the reef slope (Table 1). The epifaunal bivalve Pteria colymbus was common on the alcyonarians (Pseudopterogorgia sp. and Gorgonia sp.). Gastropods collected from the reef slope included Lithopoma caelatum, Lithopoma tectum, Coralliophila abbreviata, and Thais deltoidea (Table 1). Lithopoma caelatum and T. deltoidea were found on the bases of (Acropora palmata). The bivalves Lima scabra, Arca zebra, and Barbatia candida were also common on the reef slope. In addition, 36 species (23 gastropods and 13 bivalves) of micromollusks were collected from reef slope sediments. The most abundant species of micromolluks were the gastropod Assiminea succinea and the bivalves Pleuromeris tridentata and Carditopsis smithii. Micromollusks were also collected from sediments of the reef slope cut, a pass cutting completely through the reef slope, 10 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 approximately 150 meters to the south of isla Perez (Station 16; Fig. 2). Sediments of the reef cut yielded 24 species of micromollusks (21 gas- tropods and 3 bivalves). Caecum nitidum was the most abundant gas- tropod and Carditopsis smithii and Barbatia domingensis were the most common bivalves. Collections were made from two reef-flat areas, a high-energy area lo- cated immediately behind the windward southeast reef crest near the “Boilers” wreck (Fig. 1), and the other a lower-energy area behind the south reef crest near Isla Perez (Station 2; Fig. 2). The windward reef flat was quite broad (~300-400 m). Cerithium litteratum were commonly found on calcareous green algae (Halimeda sp.) and (Acropora cervicornis). The low-energy reef-flat area (Station 2, Fig. 2) near Isla Perez was depauperate, with few corals and algae. Coral present was a mix of both living and dead sections of elkhorn coral, on which the gastropod Lithopoma tectum and the bivalve Barbatia domingensis were common. The low-energy reef flat had more gastropod species (12:8) than did the high-energy, windward reef flat, and conversely, the windward flat had more bivalve species (5:4). Chama spp. Lithopoma spp. were common on the low-energy reef flat but absent on the windward reef flat. This is consistent with Tunnell’s (1974) observation that Lithopoma ssp.were generally absent in the areas of higher energy at Lobos and Enmedio (two southwestern Gulf of Mexico reefs). Barbatia domingensis and Columbella mercatoria were the most common bivalve and gastropod, respectively, found in both reef-flat areas. Concerning the macromollusks, the combined reef-flat habitats produced 17 species of gastropods and 7 species of bivalves (Table 1). Thirteen species of micromollusks were collected from the sediments of the windward reef flat (12 gastropods and | bivalve (Carditopsis smithii). Caecum textile was the most abun- dant micrograstopod. The Thalassia/coral area on the northeast side of Isla Perez (stations 6 & 15; Fig. 2) was reported to be dominated by thick finger coral (Porites porites) (Kornicker and Boyd (1962). However. we found only moderate coverage by Porites porites intermixed with Acropora cf. prolifera and A. cervicornis. The most commonly encountered mollusk of this area was the gastropod Pollia auritula. Ten species of gastropods and eight spe- cies of bivalves were collected from this site (Table 1). Turtlegrass (Thalassia testudinum) thrives on loose, white carbonate sands throughout Alacran. Mollusks were collected from turtlegrass beds on both the east (stations 7 & 13, Fig. 2) and west (stations 4 & 11; Fig. 2; Table 1) sides of Isla Perez.Forty-five species of mollusks (20 11 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 gastropods and 15 bivalves) were collected from seagrass-dominated habitats. Mollusks characteristic of the grassbeds were the gastropods Columbella mercatoria, Cerithium ebumeum, and Modulus modulus and the bivalves Codakia orbicularis and Brachidontes modiolus. At low tide, large numbers (~323-430 individuals/m?) of paired yellow mussel (B. modiolus) valves were observed in exposed turtlegrass beds on the east side of the island (Stations 7 & 13; Fig. 2). However, no yellow mussels, live or dead were collected from the west side-grassbeds. A total of 24 micromollusk species (22 gastropods and 2 bivalves) were collected from turtlegrass sediments (Station 11; Fig. 2). The most com- mon microgastropod found in turtlegrass sediments was Caecum nitidum. Tunnell (1974) found Caecum nitidum to be the most abundant and ubiq- uitously distributed caecid on Lobos and Enmedio reefs. Other common microgastropods included Caecum spp., Cyclostremiscus sp.,Odostomia sp., Cyclostremiscus ornatus, Dendropoma corrodens, and Tricolia cf. thalassicola. The most common microbivalve was Carditopsis smithii. Piles of coral rock formed hard-shore intertidal habitats within the lagoon on the southeast side of Isla Perez (Station 8, Fig. 2). The 19 species of gastropods and 8 species of bivalves collected from this area are characterisic of harshore intertidal habitats of the Gulf of Merxico and Caribbean Sea. These included the gastropods Pollia auritula, Leucozonia nassa, and Morula nodulosa and the bivalves Barbatia cancellaria and lsognomon radiatus. The upper mid-littoral zones of coral rocks were encrusted with the colonial gastropod Petaloconchus sp. Morula nodulosa was collected exclusively from this area. In contrast, Tunnell (1974) found Morula nodulosa in almost all reef zones at Lobos and Enmedio. The southeast and southwest points of Isla Perez are composed prima- rily of staghorn coral fragments. The southwest extension of coral rubble (Station 3, Fig. 2) present in 1986, no longer formed a small lagoon as described by Kornicker and Boyd (1962a) and Macintyre et al. (1977). All that remains of the lagoon are two bars of coral-rubble (Fig. 2). Col- lecting efforts on the southwestern rubble point yielded 10 species of gastropods and 6 species of bivalves (Table 1). Paired Codakia orbicu- laris valves were abundant among the coral rubble. The rubble spit on the southeast tip of Isla Perez (Station 9, Fig. 2) yielded 14 species of gastropods and 7 species of bivalves. The sessile bivalves Barbatia cancellaria, Spondylus americanus, and Isognomon radiatus were found inhabiting the few, scattered coral rocks in this area. The habitats con- sisting of coral rubble yielded a total of 21 species of gastropods and 11 species of bivalves (Table 1). 12 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 The Batillaria minima zone (Station 10, Fig. 2) defined by Kornicker and Boyd (1962) also referred to as the Bahia Hedionda or the Stinking Bay, is located on the south end of Isla Perez between the coral-rubble spit (Station 9, Fig. 2) and the island. Surprisingly it was dominated by Cerithium lutosum, a gastropod very similar to Batillaria minima. Folk and Robles (1964) also found Batillaria minima in this same area. The two gastropods are easily separable by differences in operculua mor- phology. In this area, shoalgrass (Halodule wrightii) was dominant. It, with some turtlegrass, supported a very large population of Neritina virginea. Folk and Robles (1964) and Kornicker and Boyd (1962) re- ported large numbers of Neritina virginea in this same area. However, Folk and Robles (1964) cited the seagrass in this area as Cymadocea manatorum, which is a synonym of Syringodium filiforme (manateegrass). Only the two mentioned gastropods were collected from this area. We did not find manateegrass inhabiting this area. Patch reef sediments of the lagoon to the east of Isla Perez yielded 15 species of microgastropods and 5 species of microbivalves. Common gastropods included Cyclostremiscus ornatus, Arene cruentata, Zebina browniana, and Marginella lavalleeana. Carditopsis smithii was the only common bivalve. A total of 15 species of gastropods and 10 species of bivalves were collected from unvegetated sand habitats on northwest side of the Isla Perez (Stations 5 & 12; Fig, 2). These areas were dominated by infaunal bivalves Codakia orbicularis and Glycymeris pectinata. Tne beach sands at Isla Pajaros (Fig. 1) yielded 45 species of micromollusks (36 species of gastropods and 9 of bivalves). The gastropod Finella adamsi was abundant in this area. Mollusks were collected from two intertidal moat areas i.e. intertidal areas of alternating sand depressions and raised mounds of seagrass- colonized sands), one between Isla Perez and the southeast-end seagrass bed (Station 12, Fig. 2) and the other at Isla Pajaros (Fig. 1). Intertidal moats at Isla Pajaros produced more gastropod (9:4) and bi- valve (6:0) species than those at Isla Perez. Cerithium lutosum and Polinices lacteus were the only species common to both sites. (Table). The molluscan assemblages atAlacran are similar to those of the West Indies and the Florida Keys (Rice and Komicker 1962). Rice and Kornicker (1962 and 1965), reported 104 gastropods and 42 bivalves from this area, of which 61% and 79%, respectively, were collected during our study bringing the total number of mollusks collected from Alacran reef to 265 18 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 species. Alacran was found to have the highest molluscan species when compared to 33 other localities along the Yucatan Peninsula including both shoreline and other coral reefs habitats (Gonzales et al., 1991). Ekdale (1974) collected 316 molluscan species at intermittent locations along the northeastern Yucatan coast and of these, 58 species of gas- tropods and 34 species of bivalves were collected in the current study. In contrast to that reported by Kornicker and Boyd (1962), no Batillaria minima were found inhabiting the Batillaria minima zone, instead we found a large population of the morphologically similar Cerithium lutosum. Rice and Kornicker (1962) do however list both Batillaria minima and Cerithium variabile (= Cerithium lutosum) as being collected from Alacran. Unfortunately the collection localities for Cerithium variabile were not provided by Rice and Komicker (1962) and no Batillaria minima were collected during the present study. Kornicker and Boyd (1962) reported densities of Strombus gigas occurred at 1-2 individuals - (0.83 m? at the south reef near Isla Perez (Stations 1 & 2, Fig. 2) as well as other loca- tions throughout Alacran. During 1986, few live queen conchs were seen in the immediate vicinity of Isla Perez, however shallow lagoon habitats further from the island had higher densities. The observed de- cline of queen conch is likely the result of over fishing, as conch fishing boats from fishing cooperatives on the mainland were removing 1500- 2000 snails per boat per 2-week fishing trip. Similar fishing practices completely extirpated queen conch from the Veracruz reefs during the 1970’s (Tunnell, 1994). Acknowledgments: Support for the work on Alacran reef was provided by a Fulbright Scholar Award to Tunnell and by financial assistance from Corpus Christi State University (now Texas A&M University-Corpus Christi). Trips to Alacran Reef were arranged by Dr. and Mrs. Ernesto A. Chavez of Centro de Investigaciones y de Estudios Avanzados del Instituto Politecnico Nacional-Unidad Merida on ships of the Armada de Mexico. Each is gratefully acknowledged. We also thank Mauricio Garduno and Alicia Gonzalez for field assistance. 14 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Literature cited: Agassiz, A. 1878-1879. Letter no. 1 to C.P. Patterson, Superintendent Coast Survey. Washington, D.C. fromA. Agassiz, on dredging operations of the U.S. Coast Steamer “Blake.” Bulletin of the Museum of Comparative Zoology, Harvard College 5(6): 1-19. Bonet, F. 1967. Biogeologia subsuperficial del Arrecife Alacranes, Yucatan (México). Universidad Nacional Autonoma México, Boletin Instituto Geologia 80:1-192. Bonet, F. and J. Rzedowski. 1962. La vegetacidn de las islas del Arrecife Alacranes, Yucatan (México). Anales de Escuela Nacional de Ciencias Biologicas, Mexico 6(1-4):15-59. Boswall, J. 1978. The birds of Alacran Reef, Gulf of Mexico. Bulletin of the British Ornithological Club 98:99-109. Boudreaux, W.W. 1987. Comparisons of molluscan reef flat assem- blages from four reefs of the Campeche Bank, Yucatan, Mexico. Professional Paper, Biology Department, Corpus Christi State University. 47pp. Chavez, E.A., E. Hidalgo, and M.A. Izaguirre. 1985. A comparative analysis of Yucatan coral reefs. Proceedings of the Fifth Inter- national Coral Reef Congress, Tahiti 6: 355-361. Davis, R.A. Jr. 1964. Foraminiferal assemblages of Aldaran Reef, Campeche Bank, Mexico. Journal of Paleontology 3 8(2): 417-421. Ekdale, A.A. 1974. Marine molluscs from shallow-water environments (O to 60 meters) off the northeastern Yucatan coast, Mexico. Bulletin of Marine Science 24(3):639-668. Folk, R.L. 1967. Sand cays of Alacran Reef, Yucatan, Mexico: Morphol- ogy. Journal of Geology 75:412-437. Folk, R.L. and A.S. Cotera. 1971. Carbonate sand cays of Alacran Reef, Yucatan, Mexico: Sediments. Atoll Research Bulletin no. Bi7/- 15 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Folk, R.L. and R. Robles. 1964. Carbonate sands of Isla Perez, Alacran Reef Complex, Yucatan. The Joumal of Geology 72(3): 255-292. Fosberg, F.R. 1961. Atoll news and comments. Atoll Research Bulletin. 84: 6-9. Fosberg, F.R. 1962. Abrief study of the cays of Arrecife Alacran, a Mexican atoll. Atoll Research Bulletin 93: 1-25. Gonzalez, A.C. 1965. Foraminiferos recientes de la familia Soritidae Ehrenberg 1839 en el Arrecife Alacranes, Banco de Campeche, Campeche, México. Tesis 42pp. Gonzalez, M.A. 1991. Distribution patterns of gastropods and bivalves at the Yucatan Peninsula, Mexico, Ciencias Marinas 17(3): 147-172. Hays, M.O. 1962. Sedimentology of Desaparecida Bar, Alacran Reef, Mexico. The Texas Journal of Science 14:415. | Hildebrand, H.H., H. Chavez, and H. Compton. 1964. Aporte al conocimiento de los peces del 14 Arrecife Alacranes, Yucatan, Mexico. Ciencia XXIll (3):107-134. Hoskin, C.M. 1963. Recent carbonate sediments on Alacran Reef, Yucatan, Mexico. National Academy of Sciences-National Research Council, Publication no. 1089. 160 pp. Hoskin, C.M. 1966. Coral pinnacle sedimentation, Alacran Reef Lagoon, Mexico. Journal of Sedimentary Petrology 36(4): 1058-1074. Kennedy, J.N. 1917. Alittle-known bird colony in the Gulf of Mexico. Ibis 10(5):41-43. Kornicker, L.S., F. Bonet, R. Cann, and C.M. Hoskin. 1959. Alacran Reef, Campeche Bank, Mexico. Publications of the Institute of Marine Science, University of Texas. 6:1-22. Kornicker, L.S. and D.W. Boyd. 1962a. Shallow-water geology and environments of Alacran Reef Complex, Campeche Bank, Mexico. Bulletin of the American Association of Petroleum Geologists 46(5): 640-673. 16 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Kornicker, L.S. and D.W. Boyd. 1962b. Bio-geology of a living coral reef complex on the Campeche Bank. In: Field trip guidebook to the Peninsula of Yucatan. pp. 73-84. New Orleans Geological Society. Macintyre, |.G., R.B. Burke, and R. Stuckenrath. 1977. Thickest recorded Holocene reef section, Isla Perez core hole, Alacran Reef, Mexico. Geology 5: 749-754. Millspaugh, C. F. 1916. Vegetation of Alacran Reef. Field Museum of Natural History, Publication no. 187. Botanical Series. 2(11): 421-431. Rice, W.H. and L.S. Kornicker. 1962. Mollusks of Alacran Reef, Campeche Bank, Mexico. Publications of the Institute of Marine Science, University of Texas. 8: 366-403. Rice, W.H. and L.S. Kornicker. 1965. (Addendum to 1962 paper). Publications of the Institute of Marine Science, University of Texas. 10: 172. Tunnell, J.W. 1974. Ecological and geographical distributions of Mollusca of Lobos and Enmedio coral reefs, southwestern Gulf of Mexico. Dissertation, Texas A&M University. 158pp. Tunnell, J.W. 1994. Natural versus human impacts to southern Gulf of Mexico coral reef resources. Proceedings of the Seventh Inter- national Coral Reef Symposium, Guam, 1992. 1:300-306. Tunnell, J.W. and Chapman, B.R. 1988. First record of Red-footed Boobies nesting in the Gulf of Mexico. American Birds 42(3): 380-381. Vaught, K.C. 1989. Aclassification of the living Mollusca. American Malacologists, Inc.16 195pp. Wright, T. and L.S. Kornicker. 1962. Island transport of marine shells on Isla Perez, Alacran Reef, Campeche Bank, Mexico. Journal of Geology 70(5):616-618. WW TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Table 1. Systematic list of mollusks collected or observed at Alacran Reef, Mexico. Habitat notations: Reef Cut -RC, Patch Reef -PR, Reef Slope -RS, Reef Flat -RF, Thalassia testudinum grassbed -Tt, Beach Sample -BS, Rocky Intertidal -RI, Carbonate Sand -CS, Coral Rubble - CR, mixed 7halassialCoral -TC, Moat -MT, Batillaria Zone -BZ, and Beach Drift BD. Abundance notations: Abundant = > 50 (A), Common = 6-50 (C), Uncommon = 2-5 (UC), and Rare = 1 (R). *Species listed by Rice and Kornicker (1962, 1965). Species Habitat (Abundance) Phylum Mollusca Class Polyplacophora Order Neoloricata Family Ischnochitonidae Ischnochiton sp. Ri(UC) Class Gastropoda Subclass Prosobranchia Order Archaeogastropoda Superfamily Pleurotomarioidea Family Scissurellidae Scissurella cingulata O.G. Costa, 1861 RF(C) Superfamily Fissurelloidea Family Fissurellidae Diodora listeri (d’Orbigny, 1842)* RC(R); BD(C) Diodora cayenensis (Lamarck, 1822) RI(C) Diodora dysoni (Reeve, 1850) RF(UC); RI(C) Emarginula pumila (A. Adams, 1852) RS(C); BS(C) Hemitoma emarginata (Blainville, 1825)* RC(R); BS(R); BD(R) Lucapina suffusa (Reeve, 1850)* BD(C) Lucapina philippiana (Finlay, 1930) BS(R) Rimula sp. RS(R) Superfamily Patelloidea Family Acmaeidae Lottia antillarum (Sowerby, 1831) TC(UC); RC(C) Lottia pustulata (Helbling, 1779)* CR(UC); Tt(UC); RI(UC) Lottia leucopleura (Gmelin, 1791) RF(UC); BD(UC) Superfamily Trochidea Family Trochidae Calliostoma javanicum (Lamarck, 1822)* BD(C) Calliostoma jujubinum (Gmelin, 1791)* © RF(UC);CR(UC); SG(UC); TC(UC); BD(UC) 18 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Tegula excavata (Lamarck, 1822) RF(R); RI(C); CR(UC) Tegula lividomaculata (C.B. Adams, 1845) BD(R) Family Stomatellidae Synaptocochlea picta (d’Orbigny, 1842)* RC(C); RF(C); RS(C); BS(C); Tt(R) Family Skeneidae Parviturbo sp. PR(C) Family Turbinidae Arene cruentata (Muhlfeld, 1829)* RC(C); PR(C); RF (C) RS(C); BS(C); Tt(C) Astralium phoebium Réding, 1798* CR(UC); SG(UC); CS(UC); RI(UC); BD(C) Gabrielona sulcifera Robertson, 1973 RC(R) Lithopoma americanum (Gmelin, 1791)* RS(C); RF(C); CR(C); SG(C); CS(R); TC(C); BD(C) Lithopoma caelatum (Gmelin, 1791)* RS(C);RF(UC); CS(UC); RI(R); CR(UC); BD(C) Lithophoma tectum (Gmelin, 1791 )* RF(R); RI(UC) Tricolia thalassicola Robertson, 1958* ~=Tt(C) Turbo cailletii P. Fischer & Bernardi, 1856* SG(UC); CR(UC); BD(UC) Turbo canaliculatus Hermann, 1781 MT(R) Superfamily Neritoidea Family Neritidae Nerita tessellata Gmelin, 1791* CR(C);MT(R);BD(UC) _ Nerita versicolor Gmelin, 1791* BD(R) Neritina virginea (Linné, 1758)* BZ(A); SG(C) Smaragdia viridis (Linné, 1758) PR(R); BS(R); BD(C) Order Mesogastropoda Superfamily Rissooidea Family Assimineidae Assiminea succinea (Pfeiffer, 1840) RS(A); PR(C) Family Rissoidae Alvania auberiana (d’Orbigny, 1842) RC(UC); BS(UC) Rissoina bryerea (Montagu, 1842) Tt(R) Rissoina cancellata Philippi, 1847 RC(R) Rissoina catesbyana d’Orbigny, 1842 RS(R) Rissoina multicostata (C.B. Adams, 1850)* BS(UC) 19 TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Rissoina sagraiana d’Orbigny, 1842 Zebina browniana (d’Orbigny, 1842)* Family Caecidae Caecum cooperiS. Smith, 1860* Caecum floridanum Stimpson, 1851* Caecum imbricatum Carpenter, 1858 Caecum insularum D.R. Moore, 1970 Caecum nitidum Stimpson, 1851 Caecum plicatum Carpenter, 1858 Caecum pulchellum Stimpson, 1851 Caecum textile de Folin, 1867 Caecum vestitum de Folin, 1870 Caecum sp. Family Vitrinellidae Circulus suppressus (Dall, 1889) BS(UC) PR(C); RF(C); BS(C) RF(C) RC(R); PR(C); Tt(C) BS(C) Tt(UC); BS(C) BS(UC) RC(A); Tt(C); BS(UC) RS(C); PR(UC); Tt(R) RC(C); RS(C) RF(A) RC(UC) RS(C) RS(C) Cyclostremiscus beauii (P. Fischer, 1857)PR(R); Tt(UC) Cyclostremiscus ornatus Olsson & McGinty, 1958 PR(C); Tt(C) Cyclostremiscus pentagonus (Gabb, 1873) RC(UC) Parviturboides interruptus (C.B. Adams, 1850) BS(R) ?Pleuromalaxis balesi Pilsbry & McGinty, 1945 Tt(UC) Teinostoma cf. biscaynense Pilsbry & McGinty,1945 Family Vanikoroidae BS(R) Macromphalina cf. palmalitoris Pilsbry and McGinty, 1950 Superfamily Cerithioidea Family Modulidae Modulus modulus (Linné, 1758)* Modulus carchedonius (Lamarck, 1822) Family Cerithiidae Cerithium litteratum (Born, 1778)* Cerithium ebumeum Bruguiere, 1792* Cerithium lutosum Menke, 1828* Finella adamsi (Dall, 1889) Finella dubia (d’Orbigny, 1842) 20 BS(R) Tt(C); RI(R); BD(UC) Tt(C) RS(UC); RF(C); CR(C); Tt(C); RUC); BD(C) BD(C) RS(R); CR(C); Tt(C); TC(UC); RIC); CS(UC) BZ(A); MT(UC); BD(UC) Tt(UC); BS(A) Tt(C) Family Turritellidae Vermicularia spirata (Philippi, 1836) Vermicularia knorrii (Deshayes, 1843)* Family Vermetidae Petaloconchus sp. TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Tt(UC); BD(C) BD(UC) TC(UC); RI(C) - Petaloconchus mcgintyi Olsson & Harbison, 1953 BD(UC) Serpulorbis decussatus (Gmelin, 1791) Tt(R); BD(UC) Dendropoma irregulares (d’Orbigny, 1842)BD(C) Dendropoma corrodens (d’Orbigny, 1842) Tt(C); BS(C) Superfamily Stromboidea Family Strombidae Strombus costatus Gmelin, 1791* Strombus gigas Linné, 1758* Strombus raninus Gmelin, 1791* Superfamily Hipponicoidea Family Hipponicidae Hipponix antiquatus (Linné, 1767)* Superfamily Crepiduloidea Family Calyptraeidae Crucibulum auricula (Gmelin, 1791) Superfamily Cypraeoidea Family Cypraeidae Cypraea cervus Linné 1771 Cypraea acicularis Gmelin, 1791 Family Triviidae Trivia pediculus (Linn6, 1758) Trivia quadripunctata (J.E. Gray, 1827)* Superfamily Naticoidea Family Naticidae Natica canrena (Linné, 1758)* Natica livida Pfeiffer, 1840* Polinices lacteus (Guilding, 1834)* Superfamily Tonnoidea Family Tonnidae Tonna maculosa (Dillwyn, 1817)* Tonna galea (Linné, 1758)* 2) BD(UC) CS(UC); BD(C) MT(R); BD(UC) RF(R); RS(R); BS(R); BD(UC) BD(R) BD(UC) BD(UC) BD(R) BD(UC) RF(R); CR(UC); Tt(UC); BD(C) MT(C) CR(UC); CS(UC); Tt(UC); MT(UC); BD(UC) CR(R); MT(R); BD(C) BD(UC) TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Family Cassidae Cassis madagascariensis Lamarck, 1822* BD(UC) Family Ranellidae Cymatium nicobaricum (Réding, 1798)* CS(R) C’ymatium pileare (Linné, 1758) * BD(UC) Cymatium caribbaeum Clench & Turner, 1957* — BD(UC) Superfamily Cerithiopsoidea Family Cerithiopsidae Cerithiopsis greenii (C.B. Adams, 1839) RS(C); Tt(UC); BS(C) Seila adamsii (H.C. Lea, 1845)* RC(R); RS(C); PR(UC);BS(UC); Tt(R) Superfamily Triphoroidea Family Triphoridae Triphora turristhomae (Holten, 1802)’ RF(R); BS(R); PR(R) Triphora triserialis (Dall, 1881) BS(R) Superfamily Epitonioidea Family Epitoniidae . Epitonium sp. RS(R) Epitonium lamellosum (Lamarck, 1822) BD(R) Superfamily Eulimoidea Family Eulimidae Melanella sp. RS(C) Order Neogastropoda Superfamily Muricoidea Family Muricidae Morula nodulosa (C. B. Adams, 1845)* — RI(C) Thais deltoidea (Lamarck, 1822)* RS(C) Coralliophila abbreviata (Lamarck, 1816) RS(C) Family Buccinidae Bailya parva (C. B. Adams, 1850) RI(R) Cantharus cancellarius (Conrad, 1846) BS(R) Engina turbinella (Kiener, 1835) RS(UC); RF(UC); RI(C);Tt(UC); TC(UC); BD(UC) Pollia auritula (Link, 1807) RS(UC); RF(C); TC(C);RI(UC); Tt(UC); CR(UC) Pollia tincta Conrad, 1846* BD(UC) Pisania pusio Linn6, 1758) BD(R) Family Columbellidae Anachis cf. hotessieriana (d’Orbigny, 1842) BS(C) 22 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Anachis pulchella (de Blainville, 1829)* Columbella mercatoria (Linné. 1758)* BD(UC) RF(C); CR(UC); Tt(C); RI(R); CS(C); BD(C) Columbella cf. rusticoides Heilprin, 1887 BD(R) Pyrene ovulata (Lamarck, 1822)* Family Nassariidae Nassarius albus (Say, 1826) Family Melongenidae Busycon contrarium (Conrad, 1840)* Busycon coarctatum (Sowerby, 1825) Busycon spiratum (Lamarck, 1816)* Family Fasciolariidae Fasciolaria tulipa (Linné, 1758)* Leucozonia nassa (Gmelin, 1791)* Pleuroploca gigantea (Kiener, 1840)* Family Harpidae Morum oniscus Linné, 1767 Family Vasidae Turbinella angulatus Lightfoot, 1786” Family Olividae Jaspidella jaspidea (Gmelin, 1791) Olivella floralia (Duclos, 1853) Family Marginellidae Gibberula sp. Hyalina lactea (Kiener, 1841) Hyalina albolineata (d’Orbigny, 1842) Hyalina avena (Kiener, 1834)* Marginella guttata (Dillwyn, 1817)* Marginella lavalleeana d’Orbigny, 1842 Marginella labiata Kiener, 1841 BD(UC) CS(R); BD(UC) CS(UC); BD(C) BD(UC) BD(C) CR(R);CS(R);BD(UC) RF(UC); RI(C); Tt(UC);CR(C); BD(R) BD(UC) RF(UC) Tt(UC); BD(UC) Tt(UC) BS(C) RS(R) BS(R) RF(R) RF(R) MT(UC); BD(UC) RC(UC); PR(C): RF(C) Tt(UC); RI(UC): CS(UC);CR(UC); BD(C) Marginella roosevelti Bartsch & Rehder, 1939 BD(R) Marginellopsis serrei Bavay, 1911 Superfamily Conoidea Family Conidae Conus mus Hwass, 1792* Conus spurius Gmelin, 1791* a RC(R); RS(C) BD(R) BD(R) TEXAS CONCHOLOGIST Vol. 38, No. 1 Family Turridae Crassispira fuscescens Reeve, 1843 Daphnella lymneiformis (Kiener, 1840) Pyrgospira ostrearum (Stearns, 1872) Agathotoma candidissima (C.B. Adams, Family Terebridae Hastula hastata (Gmelin, 1791) Superfamily Rissoelloidea Family Rissoellidae Rissoella caribaea Rehder, 1943 Subclass Heterobranchia Superorder Allogastropoda Superfamily Architectonicoidea Family Mathildidae Mathilda barbadensis Dall, 1889 Superfamily Pyramidelloidea Family Pyramidellidae Cingulina babylonia (C.B. Adams, 1845) Odostomia sp. Turbonilla sp. Eulimastoma weberi Bartsch, 1916 Subclass Opisthobranchia Order Cephalaspidea Superfamily Philinoidea Family Bullidae Bulla striata Bruguiere, 1792 Family Scaphandridae Acteocina bullata (Kiener, 1834) Family Atyidae Haminoea elegans (J.E. Gray, 1825) Atys cf. caribaea (d’Orbigny, 1841)* Family Retusidae Retusa candei d’Orbigny, 1841 Order Sacoglossa Family Elysiidae Tridachia crispata (Mérch, 1863) Order Aplysiomorpha Superfamily Aplysiodea Family Aplysiidae Aplysia dactylomela Rang, 1828 24 September, 2001 CR(UC); Tt(R) BS(R); BD(R) BD(UC) 1845) BS(R) CS(UC) Tt(C) RS(R) RC(C); RF(C); RS(C); mG. RF(C) RC(R); BD(R) RC(UC); BS(C) Tt(R); CS(R); BD(C) Tt(R) BD(R) BS(C) RS(C); PR(UC) RS(UC) MT(R) TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Class Bivalvia Subclass Protobranchia Order Nuculoida Superfamily Nuculoidea Family Nuculidae Nucula crenulata A. Adams, 1856 RS(UC) Subclass Pteriomorphia Order Arcoida Superfamily Arcoidea Family Arcidae Arca imbricata Bruguiere, 1789* RS(C); BD(UC) Arca zebra (Swainson, 1833)* RS(C); BD(C) Acropsis adamsi (Dall, 1886)* RC(R) Anadara floridana (Conrad, 1869) BD(UC) Barbatia cancellaria (Lamarck, 1819)* |§ RS(C); PR(C); RF(C); RC(C); BS(C); Tt(UC); RI(A); BD(C) Barbatia domingensis (Lamarck, 1819)* RC(C);RS(C); BS(C); RF(C); CR(R); RI(C); Tt(UC); TC(UC); BD(UC) Barbatia candida (Helbling, 1779) RS(C) Superfamily Limopsoidea Family Glycymerididae Glycymeris decussata (Linné, 1758) MT(R) Glycymeris pectinate (Gmelin, 1791)* PR(UC); Tt(C);CS(C); TC(UC); CR(UC); BD(C) Glycymeris cf. undata (Linné, 1758) BD(R) Order Mytiloida Superfamily Mytiloidea Family Mytilidae Botula fusca (Gmelin, 1791) BD(R) Brachidontes modiolus Linné, 1767* Tt(A); BD(C) Gregariella sp. RS(C) Lithophaga antillarum (d’Orbigny, 1842) RI(C) Modiolus americanus (Leach, 1815)* Tt(UC); CS(UC); BD(C) Order Pterioida Superfamily Pterioidea Family Pteriidae Pteria colymbus (Réding, 1798) RS(UC) a3) TEXAS CONCHOLOGIST Vol. 38, No.1 September, 2001 Pinctada imbricata Réding, 1798 Family lsognomonidae Isognomon radiatus (Anton, 1839)* Superfamily Pinnoidea Family Pinnidae Pinna carnea Gmelin, 1791 Pinna rudis Linné, 1758 Order Limoida Superfamily Limoidea Family Limidae Lima lima (Linné, 1758)* Lima pellucida C. B. Adams, 1846 Lima scabra (Born, 1778)* Order Ostreoida Superfamily Ostreoidea Family Ostreidae Dendostrea frons (Linné, 1758)* Superfamily Plicatuloidea Family Plicatulidae Plicatula gibbosa Lamarck, 1801 Superfamily Pectinoidea Family Pectinidae BD(C) CR(UC), RI(C); TC(UC) Tt(UC); TC(UC); CR(UC);BD(UC) BD(UC) RI(UC); Tt(UC); RF(UC);TC(C); BD(UC) RI(UC); RF(UC) RS(C); TC(UC): BD(UC) BD(C) BD(R) Aequipecten muscosus (W. Wood, 1828) Tt(UC); BD(R) Chlamys imbricata (Gmelin, 1791)* RI(UC); RF(UC); CR(R); MT(R); BD(C) Bractechlamys antillarum (Recluz, 1853)*TC(R); Tt(R); BD(UC) Nodipecten nodosus (Linn6, 1758) Family Spondylidae Spondylus americanus Hermann, 1781* Subclass Heterodonta Order Veneroida Superfamily Lucinoidea Family Lucinidae Codakia orbicularis (Linné, 1758)* 26 BD(UC) BD(C) CR(UC); CS(C); Tt(C); BD(A) TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Codakia orbiculata (Montagu, 1808)* CS(UC); Tt(UC) Divaricella dentata (W. Wood, 1815)* CS(UC); BD(UC) Divaricella quadrisulcata (d’Orbigny, 1842)* CR(UC); CS(UC); Tt(UC); BD(UC) Linga pensylvanica (Linné, 1758)* CR(UC); Tt(C); MT(UC);BD(C) Family Ungulinidae Diplodonta sp. RS(R) Superfamily Carditoidea Family Carditidae Pleuromeris tridentata (Say, 1826) Tt(UC) Family Condylocardiidae Carditopsis smithii (Dall, 1896) Tt(C) Superfamily Chamoidea Family Chamidae Chama macerophylla Gmelin, 1791 RF(UC); RI(UC); Tt(UC);TC(UC); BD(C) Chama sinuosa Broderip, 1835 RF(UC); CR(R); BD(UC) Chama congregata Conrad, 1833 BD(UC) Chama florida Lamarck, 1819 BD(UC) Chama cf. sarda Reeve, 1847 BD(R) Superfamily Cardioidea Family Cardiidae Americardia guppyi (Thiele, 1910) RS(C) Americardia media (Linné, 1758)* BD(UC) Laevicardium laevigatum (Linné, 1758)* CS(UC); BD(C) Laevicardium sybariticum (Dall, 1886) | BD(R) Trachycardium magnum (Linné, 1758) §=BD(UC) Superfamily Crassatelloidea Family Crassatellidae Crassinella martinicensis (d’Orbigny, 1842) PR(R) Superfamily Mactroidea Family Mesodesmatidae Ervilia concentrica (Holmes, 1860) RS(C) Ervilia nitens (Montagu, 1808) PR(UC) Superfamily Tellinoidea Family Tellinidae Arcopagia fausta Pulteney, 1799* MT(UC); BD(C) Psammotreta intastriata (Say, 1827)* BD(UC) Ay} TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Strigilla mirabilis (Philippi, 1841 )* Strigilla pisiformis (Linné, 1758) Tellina candeana d’Orbigny, 1842* Tellina radiata (Linné, 1758)* Tellina listeri Réding, 1798 Tellina similis Sowerby, 1806* Superfamily Veneroidea Family Veneridae Chione cancellata (Linné, 1767)* Cyclinella tenuis (Récluz, 1852) Periglypta listeri (J.E. Gray, 1838)" 28 BS(C) BS(R) BS(C) MT(UC); BD(C) BD(C) BD(C) Tt(UC); BD(C) RS(C) CS(UC); BD(C) TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 5 Fig. 1. Schematic diagram of Alacran Reef, adapted from Folk and Cotera, 1971. 29 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 ‘adAy woyog Jo/pue ‘ ‘2961. ‘pAog puke JeyoIUIOY Wo pajdepy uoneuoz jaa ‘suoieys Buyjdwes jo suoyeo0; Buysidap Zeieq ejs{ Jo Weibelp oyeweLpS “ZH QUOZ SUDINUUD DAd{sOMOYy auoz oyoujnd pad o1ay QUOZ DUNUI DLIDY NOT qUOZ snusos1Asa? D4LAd QLIP quoz pues arg Bare [BIO OAISSRUI 2 DISSDyDY | as1edS BOT DISSMpDY J - Vpatutf}] auoz Sajuod SajLiog gjqqnu s1us09104a9 n4cd 1p pay 30 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Discharge Criteria for Drilling Fluids in the Gulf of Mexico Cheryl Hood Drilling Fluids When drilling an oil well, some type of fluid must be used to cool the drilling bit, lubricate the drill string and carry the drill cuttings to the surface and to stabilize the hole being drilled. This fluid is typically a mixture where the continuous phase may be water/seawater, diesel oil, mineral oil or synthetic oil. About 95% of the fluid is comprised of the continuous phase, barite and clay. The remaining 5% is comprised of materials that are added to enhance lubricity, bore-hole stability, viscos- ity, etc. Large quantities of drilling fluids are discharged into U.S. waters each year. Many discharges are with water-based drilling fluids and their as- sociated cuttings. These fluids are essentially water soluble or dispers- ible and once discharged into the marine environment are readily diluted to minute concentrations and may be spread over a wide area. Studies indicate that by using barium tracers, evidence of these discharges may be found several hundred meters away from the platform. The effects on marine organisms are minimal since the majority of drilling fluids chemi- cals have been shown to practically non-toxic and those organisms that are covered with a thin layer of material are able to rapidly adapt to the slightly altered environment. Diesel and mineral oil-based drilling fluids, on the other hand, have been shown to be quite toxic. These fluids are high in aromatic hydrocarbons - and contain chemicals that have been identified by EPA as priority pol- lutants (i.e. benzene, toluene, phenol, etc). They do not readily disperse into the water column and the mud and cuttings fall rapidly to the sea- floor. Consequently, diesel oil-based muds and cuttings have been banned from discharge into offshore waters. Mineral oil has been restricted to conditions in which it may be used as a carrier fluid, lubricity additive or a pill. Synthetic-based drillings fluids were developed in the early 1990’s in order to achieve lubrication and stability properties of diesel and mineral oil-based fluids. This class of fluids has been shown to be much more environmentally friendly. Synthetic oils are derived from purified chemi- cals unlike diesel and mineral oils which are derived from crude oils. Bulk discharges of synthetic oil-based fluids do not intentionally occur since they are quite expensive. Recycling of these fluids is a routine 31 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 procedure. Unfortunately when discharged, drill cuttings coated with these fluids do not readily disperse into the water column. They form globs and sink rapidly to the ocean floor forming cuttings piles that may significantly alter the ecosystem on the seafloor. The zone of impact is usually restricted to the area close to the rig site. Regulatory Requirements The discharge of drilling fluids and the associated drill cuttings into navi- gable waters of the United States are governed by Section 402 of the Clean Water Act. The U.S. Environmental Protection Agency (EPA) in Washington, D.C. writes general guidelines outlining pollution prevention methods. Each EPA region then administers these laws through Na- tional Pollutant Discharge Elimination System (NPDES) permits. Spe- cific requirements are written into the permits to allow discharge into the marine environment. Numerous macro-invertebrates, fishes and amphibians have been used in toxicity testing in an effort to develop appropriate pollution control parameters. This work formed the basis of toxicity testing today. Through modifications and work with the U.S. Army Corps of Engineers on test- ing of dredged materials, more appropriate tests have been developed to monitor drilling fluids discharges into coastal and marine environments. Larval, juvenile and molting crustaceans have been found to be more sensitive to drilling fluids than most other species and life stages. The organism selected to be a representative indicator of effects of water- based drilling fluids is Mysidopsis bahia. M. bahia is a marine/estuarine crustacean commonly found in the Gulf of Mexico. Its range extends from Laguna de Tamihue, Mexico, eastward to Cape Sable, Florida and northward to Virginia. Mysids are also amenable to laboratory culturing and testing. Their life cycle is 3-4 months long; young are produced every 5-7 days once the female reaches reproductive maturity. The young are produced in the female’s “brood-pouch” similar to marsupials. All larval stages are undergone within the pouch and, upon hatching, are smaller versions of the adults. In the laboratory, culture systems are designed so that newly hatched mysids may be harvested on a daily basis and placed into holding tanks. Juveniles may be used in the Drill- ing Fluids Toxicity Test when they are 3-6 days old. As part of the NPDES permit for the Gulf of Mexico, a drilling fluid sample is taken monthly and at the completion of drilling. This sample is shipped to a testing laboratory where a dilution of "mud” and seawater is pre- 32 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 pared and used as the test solution. Groups of twenty organisms are exposed to three replicates of five different test concentrations plus a set of clean seawater controls. The testis run for 96 hours and at termina- tion the number of surviving mysids are counted. From this data, a LC50 (lethal concentration that kills 50% of the test organisms) is calculated for the sample. These samples must have a LC50 of greater than or equal to 30,000 ppm of the suspended particulate phase to stay in com- pliance with regulations and to avoid hefty fines. Proposed Regulations Significant problems have been identified on how to appropriately moni- tor the environmental impact of synthetic discharges on the marine envi- ronment. For quite a few years, the EPAhas continued to allow, without formal approval or disapproval, the oil and gas industry to monitor these fluids using discharge requirements outlined by EPA governing water- based and oil-based drilling muds and cuttings. As long as these re- quirements have been met, there have been no objections to discharges of cuttings coated with synthetic-based drilling fluids. In 1998, the US EPA began reviewing information generated on syn- thetic-based drilling fluids in order to make a formal ruling on their dis- charge status. Workgroups were formed to address information needs outlined by EPA including bioaccumulation potential, biodegradation, _ sediment toxicity, sheen characteristics and a fate and effects study. To fund research on these topics, the oil companies, chemical companies and oilfleld service companies formed a research consortium raising over $3,000,000. Some of the data reviewed by EPA has been from the North Sea coun- tries. The United Kingdom has been reducing synthetic discharges by 25% annually to aftain zero discharge by this year’s end. Much contro- versy surrounds whether their numerous studies using multiple organ- isms and methods have led to the correct decision to ban synthetic discharges. Most of the world has been eagerly yet anxiously observing this activity. Some countries have begun adopting similar legislation. In the US, industry representatives have steadfastly maintained that envi- ronmental conditions in the Gulf of Mexico are sufficiently different from that of the North Sea. The impacts may not be as significant as has been proclaimed by other regulators and the Gulf of Mexico must be evaluated on its own merit. The US industry research workgroups have been working at a frantic pace to evaluate methods proposed by EPA, develop alternate methods and generate sound data on the effects of synthetic-based drilling fluids. 33 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Preliminary indications show that indeed the Gulf of Mexico is signifi- cantly different from the North Sea. Elevated temperatures in the Gulf of Mexico can significantly enhance biodegradability of synthetic fluids. Ocean currents and storms have been key in moving and distributing cuttings such that few cuttings piles have been located at offshore plat- forms. From a toxicity perspective, research is confirming that the cur- rent synthetics are significantly less toxic than diesel and mineral oils. In addition, literature reviews indicate that the molecules of the majority of synthetic fluids are too large to bioaccumulate in animal tissues. By December 31, 2000, the oil and gas industry will know the fate of synthetic oil-based mud cuttings discharges. Fortunately, the workgroups and review committees have been working very closely with EPA. It appears that synthetic-based drilling fluids cuttings will be approved for discharge. The monitoring requirements are still being negotiated but it appears that they will include a newly validated biodegradation, sedi- ment toxicity test using the amphipod Leptocheirus plumulosus, reverse phase extraction test for determination of crude contamination, and an industry-wide seafloor monitoring program. | The Drift Line Darwin Alder Date: January, 2001 Conditions: Low tide Pacific Coast of Panama from January 3-13, 2001 Collection Sites: Gobemadora Island Cebaco Island Islas Secas Methods: Dredging Snorkling Wading Beach combing Turning rocks Walking along sand bars and intertidal flats Beach Finds at Gobernadora Island: Conus patricius Pleuroploca princeps 34 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 Thais melones Stombus granulatus Stombus peruvianus The Houston Conchology Society Announces the Harold W. Harry Memoria! Award for 2002 All Paper work must be submitted by May 1, 2002. Announcement will be made by June1, 2002. (see insert). For Information Contact: Dr. John Wise Malacology, Houston Museum of Natural Science 1 Hermann Circle Dr. Houston, TX 77030 (O) (713) 639-4677; (Fax) (713) 639-4767 - jwise@hmns.org The Houston Conchology Society announces the Constance E. Boone Grants to Maiacology - The grant provides up to $1000 to qualified persons undertaking research on recent mollusks. Awards will be made only to citizens or permanent residents of the Ameri- cas (i.e North, Central and South America), particularly under-graduate and graduate students. (see insert for further information.) Postmark deadline is March 1, of each year with a decision to be made by April 15. Applications must be submitted in TRIPLICATE by regular mail to: Dr. John B. Wise Houston Museum of Natural Science One Hermann Circle Dr. Houston, TX 77030-1799 Questions? Email Dr. Wise-jwise@hmns.org 35 TEXAS CONCHOLOGIST Vol. 38, No. 1 September, 2001 36 HOUSTON CONCHOLOGY SOCIETY, INC. Officers 2001-2002 President: Program Vice President: Field Trip Vice-President: Treasurer: Recording Secretary: Corresponding Secretary: Chery! Hood Nancy Mustachio Frank & Tina Petway Angie Marsland Rachel Zelko Nancy Barziza Directors: Darwin Alder Lucy Clampitt Steve Browning Immediate Past President: Co-Editor, Texas Conchologist Co-Editor, Texas Conchologist Rusti Stover Joyce Martin John Zelko Constance E. Boone(d) Dr. John Wise Darwin G. Alder Honorary Life Member Dr. Helmer Odé TEXAS CONCHOLOGIST Vol. XXXVIII, No. 1, SEPTEMBER, 2001 TTUTION LI LIBRARIE “wii | Table of Contents Fissurella rosea in Texas Roe Davenport, Jr. .........eseessseseeseeseeees Sentence onneneeee 1 South Padre Island, Texas. A List of Live Collected Mollusks from the Coast Guard Station Tidal Flats. Roe Davenport, Jr. vccc.cccsscooneesssecaestee yeeseee eee 2 , Ecological Distribution of Shallow-Water Mollusca on Alacran Reef, Campeche Bank, Yucatan, Mexico David W. Hicks, Noe C. Barrera, and John W. Tunnell, Jr. ............cccccceeees 2 8 Discharge Criteria for Drilling Fluids in the Gulf of Mexico Cheryl HOOd........0cccs.ceeedcsececescconanrsseseee ose eee 31 The Drift Line .a-.-.-....02:00.:02-.cteessenes conree sede vsereeeet eee 34 The Harold W. Harry Memorial Award 2002................... 35 The Houston Conchology Society Announces the Constance E. Boone Grant to Malacology.......... 35