121 



Lyropecten subnodosus (Linne, 1758) 

 Microcardium transversum Rehder 



and Abbott, 1951 

 Nuculana jamaicensis (Orbigny, 1842) 

 Pecten papyraceus (Gabb, 1873) 

 Pilar cor data (Schwengel, 1951) 

 Poromya granulata Nyst and 



Westendorp, 1839 

 Solecurtus sanctaemarthae (Orbigny, 1853) 

 Trigoniocardia media (Linne, 1758) 

 Verticordia ornata (Orbigny, 1846) 



Gastropods 

 Conus clarki Rehder and Abbott, 1951 

 Distorsio mogyntyi Puffer and 



Emerson, 1956 

 Muricopsis hexagona Lamarck, 1822 

 Polystira albida (Perry, 1811) 



{— Pleuroliria) 

 Sconsia striata (Lamarck, 1816) 

 Turritella exoleta (Linne, 1758) 



Echinoderms 

 Astropecten duplicatus Sladen 



Crustaceans 

 Rhaninoides louisianense Rathbun 



No equivalent at this depth^ 

 Nemocardiumcentifilosum (Microcardium) 



Nuculana laeviradius 



No equivalent in eastern Pacific 



Pitar catharius 



Cyathodonta dubiosa? 



Solecurtus broggii Pilsbry and 

 Olsson, 19411 



No equivalent at this depth- 

 No equivalent at this depth^ 



Gastropods 

 Conus arcuatus 



Distorsio constrictus 

 Ocenebra sloati 



Pleuroliria oxytropis 



No equivalent in eastern Pacific 



No equivalent at this depth^ 



Echinoderms 

 Astropecten calif ornicus 



Crustaceans 



No equivalent at this depth^ 



1) These species were collected alive from this environment in a series of samples collected 

 by Joseph R. Curray in November, 1961. All were analyzed, but not included in computer 

 data. 



^) The twin of the Gulf of Mexico species was taken in either slightly less or slightly greater 

 depths. 



It is significant that the major offshore shrimp grounds (Hildebrand, 

 1954) are located on silty clay bottom in depths of 75 to 126 meters (40 to 

 65 fathoms) in both Gulfs. Preliminary observations of the shrimp grounds 

 in the Gulf of Thailand (J0RGEn Knudsen, personal communication) also 

 indicated about the same invertebrate composition for similar depths. In 

 all probability, shrimp (Penaeid) grounds in sub-tropical and tropical 

 regions throughout the world have a similar composition where the inverte- 

 brate genus or sub-genus is concerned. 



Most of the lamellibranch species found on the clayey bottoms of the 

 outer shelf are thought to be deposit feeders or suspension feeders sub- 

 sisting upon organic material occurring close to the bottom. The majority 

 of the gastropods are predators. Those species which are not predators are 

 in the family Calyptraeidae, and are epifaunal in habitat. The feeding type 



