EXPLANATION OF NEW PLATES. 311 



FIG. 



504. The same, shewing the umbones. 



505. Pleurorynchus, fossil, (from Mineral Conchology.) 



Fam. Phyllidiana. 



506. Chiton fascicularis. Phakellopleura, Guild. 

 507- — — amiculatus. Amicula, Gray. 



Fam. Calyptracea. 



508. Scutella, Brod. Internal view. 



509. External view of the same. 



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



Gray. Enlarged view. 



511. The same, natural size. 



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



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



Fam. Colimacea. 



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, natural size. 



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



523. The same, dorsal view. 



524. Pupinavitrea 



526. ■ antiquata. 



527. Namezii. 



528. — - lubrica. Callia? Gray. 



529. Cyclostoma, a pupiform species. Megalomastoma, Guild. 



530. Planorbulum. Cyclotus, Guild. 



531. a similar species, with the complicated notch at 



the posterior part of the aperture. Pterocyclos, Gray. 



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



tella, Sw. 



