35 
1036 Pisidium ultramontanum Prime. 
1704 Pisidium scutellatum 
1168 Pisidium variabile Prime. 
51 Pisidium virginicum 
997 Pilidium fulvum Muller. 
2150 Pitaria Newcombiana Gabb. 1865. 
2151 +#£=Pitaria unicolor Sby. 1835. 
2153  Pitaria vulnerata Brod. 1835. 
2154 Pitaria lupanaria Lesson. 1832. 
2155 + Pitaria rosea Brod. & Sby. 1829. 
2156 P: (Lamelliconcha) concinna Sby. 1835. 
2157 FP: circinata alternata Brod. 1835. 
998 Placiphorella latior Carpenter. 
999 Placiphorella imporcata Carpenter. 
1000 Placiphorella sinuata Carpenter. 
1001 Placiphorella velata Carpenter. 
331 Placunanomia macroschisma Desh 
2294 Planaxis nigritella Forbes. 
2295 Variety —? 
1002 Planorbis ammon Gould. 
37 Planorbis bicarinatus 
1682 Planorbis callioglyptus 
36 Planorbis campanulatus 
1004 Planorbis deflectus Say. 
1005 Planorbis exacutus Say. 38 
3171 Planorbis Gracilentus Gould, 1855. 1006 
1007 Planorbis hornii Tryan. 
39 Planorbis Lentus 
1008 Planorbis opercularis Gould. 
2131 £=Planorbis Liebmanni Dunker. 
1994 Planorbis opercularis multilineatus 
1683 Planorbis opercularis oregonensis 
40 Planorbis parvus 
1217 Planorbis trivolvis Say. 
1680 Planorbis centervillensis Tryon. 
1710 Planorbis nautileus L. 
2329 Planorbis petenensis Morel. 
1012 Planorbis tumidus Pfeiffer. 
1658 Planorbis umbilicatellus Cockerell. 
1013 Planorbis vermicularis Gould. 
332 Platidia anomioides (Scacchi) Costa var? 
279 Platyodon cancellata Conr 
1014 Plectodon scaber Carpenter. 
1015 Pleurobranchus californicus 
1372 Pleurotoma callicesta. Acapulco. 600 fms. 
1562 Pleurotoma Carpenteriana Gabb. 
2427 Pleurotoma (Antiplanes) Catalinze 
1371 Pleurotoma circinata 
2430 Pleurotoma (Genota) Cooperi Arnold. Quaternary. 
1016 Pleurotoma hemphillii 
1017 Pleurotoma montereyensis 
1018 Pleurotoma luctuosa Hinds 
1366 Pleurotoma (Antiplanes) perversa Gabb. 
1368 Pleurotoma (Antiplanes) piona. Bering sea. 
2428 Pleurotoma (Genota) Riversiana 
1370 Pleurotoma (Antiplanes) santarosana 
2426 Pleurotoma (Genota) Stearnsiana 
1369 Pleurotoma (Antiplanes) thalea 
2429 Pleurotoma (Genota) Tryoniana Gabb. Tertiary to recent. 
1019 Pleurotoma tuberculifera Gray. 
