EXPLAIiTATIOIf OF NEW PLATES. 335 



TIQ. 



509. Exiernal view of the same. 



510. Ancylus, a reversed species, illustrating the genus Velletia, 



Gray, enlarged view. 

 oil. The same, natural size. 



512. Pedicularia. Enlarged iigure, (copied from Swainson.) 



513. The same, natural size, growing on coral. 



514. Achatina ? octona. Macrospira, Guild. 



515. Stenopus cruentatus, Guild. Under side. 



516. ■ lividus. 



517. Helix, the aperture covered by the epiphragm. 



518. Pupa secale, Drap. Abida, Leach. 



519. pagoda. Gonidomus, Sw. 



520. Truncatella, enlarged figure. 



521. The same, uatin-al size. 



522. Auricula caprella. Gen. Caprella, Nonnul. Front view. 



523. The same, dorsal view. 



524. Pupina vitrea. 



526. antiquata. 



527. — Namezii. 



528. ■ lubrica. Callia ? Gray. 



529. Cyclostoma, flavulum. Megalomastoma, Guild. 

 530. Planorbulum. Cyclotus, Guild. 



531. a smaller species, with the complicated notch at 



the posterior part of the aperture. Pterocyclos, Benson. 



532. Helicina acutissima, nobis. Yiew of the under side. Trocha- 

 tella, Sw. 



533. The same in profile. 



534. \ 



535 S Strophostoma, Desh. Three views. 



536. 5 



537. Paludina impura. Bithinia, Gray ? 



538. Ampullaria avellana. Amphibola Schum. 



539. A species of Ampullaria, having a thickened ledge on which 



the shelly operculum rests. Pachystoma, Gudd. changed 

 to Pachylabra, Sw. 



