334 



EXPLANATION OF THE NEW PLATES. 



XXIT. to XXVIII. 



489. Pyrgoma monticularia. Sub-genus, Daracia, Gray, back and 



front. 



490. The same, in situ. 



491. Lyonsia Norregica. Anatina, Nonnul. Inside view of both 



valves. 



492. Outside, vtith. the valves closed. 



493. Naeara longirostrum, Anatina longirostris. Lam. Inside of 



both valves. 



494. Outside, with both valves closed. 



495. A smaller species of Ngeara, shewing the inequality of the 



valves. 



496. Amphidesma tennis. Abra. Leach. 



497. ErviUia nitens. 



498. Potamomya, of some authors. A fresh-water shell, resem- 



bling Corbula. Outside, valves closed. 



499. Inside of both valves. 



500. Cyclas amnica. Pera, Leach. 



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.) 



506. Chiton fascicularis. Phakellopleura, Guild. 



507. amiculatus. Amicula Gray. 



508. Scntella, Brod. Internal view. 



