472. Nummulites buticularis, outside. Helicites, Bl. Camerina, Brookes. 473. The same inside, to shew the chambers. 474. Nautilus pompilius, young. See Frontispiece. 475. Simplegas sulcata. 476. Endosiphonites. (from Camb. Philos. Trans.) _Fam._ Ammonacea. 477. Ammonoceras. (from Blainville.) 478. Ammonites; _a_, break in the shell, showing the sinuous septa. 479. Orbulites crassus. Globulites, Nonnul. Angulites, Montf. reduced. 479*. ---- discus. Aganides, Montf. 480. Goniatites striatus. 481. Scaphites æqualis. 482. Crioceratites Duvallii. 483. Turrilites tuberculatus. 484. Baculites Faujasii. Portion near the centre. 484*. Hamites cylindricus; _a_, internal cast of part of the shell; _b_, hollow external cast of the remainder. _Second Division._ Monothalamous Cephalopoda. 485. Argonauta Argo. 486. Bellerophon tenuifasciata. (from Sow. Gen.) 487. The same, shewing the dorsal keel. _Order._ HETEROPODA. 488. Carinaria Mediterranea. * * * * * EXPLANATION OF THE NEW PLATES. _Order._ SESSILE CIRRIPEDES. 489. Pyrgoma monticularia. _Sub-genus_, Daracia, Gray, back and front. 490. The same, in situ. _Fam._ Myaria. 491. Lyonsia Norvegica. Anatina, Nonnul. Inside view of both valves. 492. Outside, with the valves closed. 493. Næra longirostrum. Anatina longirostris, Lam. Inside of both valves. 494. Outside, with both valves closed. 495. A smaller species of Næra, shewing the inequality of the valves. _Fam._ Mactracea. 496. Amphidesma tennis. Abra, Leach. 497. Ervillia nitens. _Fam._ Corbulacea. 498. Potamomya, of some authors. A fresh-water shell resembling Corbula. Outside, valves closed. 499. Inside of both valves. Fluviatile Conchacea. 500. Cyclas amnica. Pera, Leach. _Fam._ Cardiacea. 501. Cardilia semisulcata. Isocardia semisulcata, Lam. Internal view. 502. External view of the same valve. 503. Cardium apertum. Papyridea, Sw. 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.