496 UNIONINJE. 



satur, Lea. tigris, Ferns. 



securis, Lea. trigonus, Lea. 



solidus, Lea. triqueter, Rafin. 



Sowerbianus, Lea. Troschelianus, Lea 



striatus, Lea. Troostensis, Lea. 



subovatus, Lea. trossulus, Lea. 



succissus, Lea. truncatus, Swains. 



sulcatus, Lea. tumescens, Lea. 



Taitianus, Lea. zigzag, Lea. 



Sub-gen. canthyria, Swainson. 



Shell not winged, sub-trigonal ; surface of valves spinous. 

 Cardinal teeth long, compressed. 



collinus, Com: spinosus, Lea. 



Sub-gen. iridea, Swainson (Tritogenia, Orthonymus, Agass.). 



Shell not winged, wide ; surface of valves nodulous. 



cylindricus, Say. Novse Hollandia3, Gray. 



granosus, Brag. verrucosus, Ha fin. 



Leaii, Gray. 



Sub-gen. rotundaria, Rafinesque (Cyprogenia, Agass). 



Shell not winged, sub-rotund or oblique ; surface of valves 

 nodulous. 



iEsopus, Green. nodulosus, Wood. 



caperatus, Lea. perplexus, Lea. 



Cooperianus, Lea. pustulosus, Lea. 



dromas, Lea. stegarius, Rafin. 



graniferus, Lea. tuberculatus, Rafin. 



Kienerianus, Lea. turgidus, Lea. 



Laraarckianus, Lea. varicosus, Lea. 



