UNIVALVES.— BULLA. 89 



Division III. — Shell thin, gibbous, and aperture 



LARGE. 



Family 1. — Apex generally umhilicated and without a spire, 

 Naucum — Sea-nut. Amygdalus — Jbnond. 



*Aperta — Wide. *Lignaria — Brmvn-striated. 



*Catena — Chain. Pectinata — Pectinated. 



•Plumula — Feather. Soluta — Unsealed. 



*Hydatis — Paper. *Akera — Elastic. 



Ampulla — Pewet's-egg. Cylindrica — Cylindric. 



Velum — White- banded. 



Shells Minute. 

 ♦Cylindracea — Cylindrical. *Retusa — Blunt. 



*Umbilicata — Umhilicated. *Obtusa — Obtuse. 



Family 2. — Having a spire. 

 Physis — Striped. Zonata — Zoned. 



Amplustre — Banded. Undulata — Undulated. 



Scabra — Rough. 



Division IV. — Shell pyriform, with produced beak. 



¥\c\x.s—Fig. Rapa — Turnip-shap'd. 



Pyrum — Pear. Canaliculata — Channelled.' 



Division V. — Shell generally thin, spire prominent, 

 and body whirl inflated. 



Voluta — Folate. Strigata — Yellow-streaked. 

 Dominicensis — Nine-whirVd. Striatula — Striated. 



Crassula — Reversed. Exaiata — Wrinkled. 



*FontinaIis — Fresh-water. Truncata — Truncated. 



*Rivalis — River. Priamus — Priam. 



*Hypnorum — Slender. Zebra — Zebra. 



Gelatinosa — Gelatinous. Achatina — Broad strip'd. 



Virginea — Ribbon. Purpurea — Purple-mouth'' d. 



Fasciata — Banded. Sinistrorsa — Great-revers'd. 



Division VI. — Shell cylindrical, with a subulate spire 



AND truncate BASE. 



Terebellum — Aid-shaped. 



