58 



Many of the really abundant forms are epifaunal in nature (actually 

 attached to objects on the bottom), which can be attributed to the nature 

 of the bottom, being in many places a shell-sand, with large quantities of 

 dead shell furnishing a place for attachment. These animals, Heterocyathus, 

 and two species of Astrangia (corals), the immense numbers of Calyp- 

 traeidae {Calyptraea, Crucibulum and Crepidula), the equally numerous 

 barnacles and pagurids living in dead gastropod shells, are dominant in a 

 sense, but cannot be considered part of the infaunal level-bottom com- 

 munity. The most abundant infaunal animals were the prosobranchs, 



Table IV. 



Species 



Index Group Numbers 



J 



64 



74 



Gastropods 



Crepidula arenata 



Crepidula excavata 



Polinices intemerata 



Polinices reclusianus 



Strombus gracilior (Index species grp. 64). . . 



Hexaplex erythrostomus 



Distorsio decussatus 



Nassarius versicolor 



Strombina gibberula 



Olivella fletcherae 



Terebra specillata 



Acteocina angustior 



Lameilibranchs 



Nuculana elenensis 



Barbatia alternata 



Anadara obesa 



Lioberus salvadoricus 



Chlamys circularis (Index species grp. 2) . . . . 



Lucina prolongata 



Ciena mexicana 



Laevicardium elatum 



Laevicardium elenense (Index species grp. 7) . 



Trachycardium panamense 



Trigoniocardia biangulala 



Megapilaria squalida 



Dosinia dunkeri 



Chione mariae 



Tellina amianta 



Tellina inaequistriata 



Macoma siliqua 



Semele guaymasensis 



Donax gracilis (Index species grp. 74) 



Ensis californica (Index species grp. 3) 



Crustaceans 

 Portumts pichelinqui 



{continued) 



