MOLLUSCA. LAMELLIBRANCHIA 231 



Pterinopecten, Schizodus, Protosekizodus, Carbonicola ( = Anthracosvi), 

 Anthracomya, Edmondia, Sanguinolites, Cardiomorpha. 



Permian. Bakevellia, Schizodus, Pseudomonotis (Eumicrotis). 



Trias. Nucida, Nuculana, Palceoneilo, Gervillia, Iloernesia, 

 Pterin, Monotis, Cassianella, Halobia, Ostrea, Pecten (subgenera), 

 Lima, Myophoria, Megalodon, Cardium, Palceocardita. 



Jurassic. Nucida, Nuculana, Area, Grammatodon, Myoconcha, 

 Modiola, Hippopodium, Pteria, Pseudomonotis, Gervillia, Perna, 

 Pinna, Ostrea, Gryphcea, Alectryonia, Pecten (various subgenera of), 

 Lima, Cardinia, Trigonia, Diceras, Cardium, Unicardium, Astarte, 

 Opis, PacJujrisma, Pleuromya, Ceromya, Gresslya, Pholadomya, 

 Homomya, Goniomya, Thracia. 



Cretaceous. Nucida, Area, Cucullcea, Modioli, Myoconcha, 

 Gervillia, Inoceramus, Perna, Pteria, Aucella, Ostrea, Exogyra, 

 Alectryonia, Pecten (the subgenera Chlamys, Syncyclonema, Neithea, 

 etc.), Lima, Spondylus, Plicatula, Unio, Trigonia, Hippurites, 

 Radiolites, Sphcerulites, Cardium, Protocardia, Thetironia, Cyprina, 

 Cyrena, Callista, Pleuromya, Pholadomya. 



Eocene. Nucida, Area, Pectuneulus, Pinna, Pecten {Chlamys, etc.), 

 Ostrea, Chama, Cardium, Venericardia, Cardita, Astarte, Crassa- 

 tellites, Cyprina, Lucina, Cyrena, Corbicula, Meretrix, Psammobia, 

 Tellina, Corbula, Panopcza, Pholadomya. 



Oligocene. Mytilus, Dreissensia, Ostrea, Cyrena, Corbula, 

 Erodona ( = Potamomya), Lucina, Meretrix, Venus, Psammobia. 



Pliocene. Nucida, Pectuneulus, Mytilus, Pecten, Chlamys, Cardium, 

 Cardita, Astarte, Cyprina, Lsocardia, Lucina, Venus, Dosinia{ = Ar- 

 temis), Tellina, Mya, Pholas, Thracia. 



CLASS II. GASTEROPODA 



Well-known examples of the Gasteropoda are the snail, 

 the whelk, and the cowry. The bilateral symmetry, so 

 characteristic of the lamellibranchs, is generally to a large 

 extent obliterated, owing to the twisting of the visceral 



