594- PHILOSOPHY OF ^^OOLOGY. 



Lepas. The two lateral plates at the summit of the 

 shell are very large, nearly covering the whole of the com- 

 pressed body, and having attached to it the large adductor 

 muscle. The two valves which protect the sides of the ab- 

 domen are much smaller, and somewhat triangular, while 

 the dorsal one is narrow and convex externally. The 

 branchiae are four in number, two on each side of the 

 thorax, near the origin of the first pair of feet. The Bri- 

 tish species are four in number, L. anatifera, anserifera, 

 sulcata, and fascicidai-i.s. 



Otion. This genus was instituted by our zealous and 

 intelligent friend Dr Leach, whose labours have greatly 

 contributed to improve the classification of the genera of 

 this class. The body is but slightly compressed, and the 

 valves are very small and distant from one another, the 

 whole being chiefly covered by its membranaceous cloak. 

 At the extremity of the abdomen, the cloak terminates in 

 two tubular appendages. Through these the water escapes 

 which has been taken in at the ventral aperture, and lias 

 passed along the surface of the gills. The gills are sixteen 

 in number, eight on each side, the first pair on each 

 side resembling those of the Lepas, the remaining six are 

 attached to the base of the feet. There are two British 

 species. 1. O.aurita, Cuvier, Mem. des Anatifes, Fig. 12, 

 13. A specimen of this was found on the Dawlish coast, 

 Devon, by Mr Comyns. 2. O. cornuta, taken alive from 

 the bottom of a transport stranded on the coast of De- 

 von, by Montagu, and described and figured by him, 

 Lin. Trans, vol. xi. p. 179, tab. xii. f. 1. 



CiNERAs. This genus was likewise instituted by Dr 

 Leach. The valves are equally minute and remote as in 

 the preceding genus, but there is here no appearance of tu- 

 bular appendages to the cloak. The C. membranacea, first 

 described and figured by Montagu, Lin. Trans, vol. ix. 



