117 



Gulf of Mexico 



Scaphopods 

 Dentalium gouldii 

 Cadulus carolinensis 



Gastropods 

 Calyptraea centralis 

 Natica floridana 

 Strombus alatus 

 Semicassis granulatus 

 Ficus carolae 



Murex recurvirostris rubidus 

 Nassarius ambiguus 



Pelecypods 

 Chlamys gibbus gibbus 

 Pecten ravenelli 

 Crassatella speciosa 

 Crassinella martinicensis 

 Liicina sombrerensis 

 Trigoniocardia media 

 Papyridea soleniformis 

 Laevicardium laevigatum 

 Microcardium tinctum 

 Gouldia cerina 

 Chione clenchi 

 Tellina tayloriana 

 Tellina lintea 

 Tellina squamifera 

 Macoma extenuata 

 Solecurius cumingianus 



Gulf of California 



Scaphopods 

 Dentalium oerstedii 

 Cadulus perpusillus 



Gastropods 

 Calyptraea mamillaris 

 Natica idiopoma 

 Strombus gracilior 

 Semicassis centriquadrata 

 Ficus ventricosa 

 Murex r. recurvirostris 

 Nassarius pagodus 



Pelecypods 

 Chlamys circularis 

 Pecten vogdesi 

 Crassatella gibbosa 

 Crassinella pacifica 

 Lucina excavata 

 Trigoniocardia biangulata 

 Papyridea aspersa 

 Laevicardium elatum 

 Microcardium pazianum 

 Gouldia calif ornica 

 Chione mariae 

 Tellina inaequistriata 

 Tellina reclusa 

 Tellina fluctigera 

 Macoma siliqua 

 Solecurtus guaymasensis 



There are many more mollusks and other invertebrate species in this 

 environment in both gulfs, which are identical in appearance, and which 

 give similar aspects to both areas. The geological occurrences of most of 

 the pelecypods taken in the Gulf of California in this study can be found 

 in Olsson (1961). A surprising number of the species were found to occur 

 in middle Tertiary formations. Likewise, the twins of these species in the 

 Gulf of Mexico or their precursors have also been described from Tertiary 

 deposits of Florida (Dall, 1890b-1903) and the Caribbean (Woodring, 

 1925, 1928). Many of these twin species have identical depth, temperature 

 and sediment "preferences" today in both oceans. It is therefore possible 

 that large portions of the Central and South American Mio-Pliocene 

 seaways may have been represented by sand bottom at about these depths. 

 Here then, is another instance of the importance of the geological setting 

 influencing the composition of assemblages or communities. Tectonic 



