EMARGINULA. MOLLUSCA. 65 



Gen. 16. EMARGINULA, Lam. Patella, Lin. 

 Animal with two conical tentacula, with the eyes at the base ; 

 mantle large, partly covering the shell with its border ; foot 

 large and thick. Shell a conical shield, with the summit in- 

 clined ; cavity simple, with a fissure or notch at the posterior 

 margin. 



E.jissura, Lam. Shell ovate, convex-conical, with longitudinal ribs 

 and transverse striae ; brownish white ; marginal fissure narrow 

 and deep ; summit recurved. 6 lines long. Inhabits European 

 coasts. B. Browns Illust. pi. 36, fig. 17, 19. 



Fossil species of this genus are found in England in oolite. 



Gen. 17. PARMOPHORUS, Lam. Patella, Chem. 

 Animal with the body thick, oblong, oval, obtuse at the extre- 

 mities, with a mantle, of which the border, cleft before, falls 

 vertically around ; head distinct ; two almost pediculated eyes 

 at the base of the tentacula ; branchial cavity opening ante- 

 riorly behind the head by a transverse cleft. Shell oblong, 

 slightly convex above, notched anteriorly, with a pointed apex 

 inclined backwards. 



P. Australia, Lam. Shell oblong, solid, depressed, with the pos- 

 terior margin rounded, and the anterior truncated. 2 inches long. 

 Inhabits coasts of New Holland. Chem. xi. pi. 197, fig- 1918. 



FAMILY V. SEMIPHYLLIDIACEA. 



Branchiae placed under the margin of the mantle, and disposed 

 in a longitudinal series on the right side of the body ; respir- 

 ing in water. 



Gen. 18. UMBRELLA, Lam. Patella, Gmel. 

 Animal with the body very thick, oval, furnished with a dorsal 

 shell ; foot simple, smooth and flat below, bordered around, 

 notched anteriorly, and attenuated behind ; head indistinct ; 

 four tentacula, the two upper thick, short, and truncated ; 

 the two others thin, in the form of pediculated crests ; bran- 

 chiae foliaceous. Shell external, orbicular, slightly convex 

 above, with the apex towards the middle. 



U. Indica, Lam. Shell whitish, summit yellow, slightly concave 

 beneath, roundish, with concentric wrinkles and longitudinal 

 striae ; interior yellowish, with radiated striae. 4 inches in dia- 

 meter. Indian seas. Chem. x. pi. 169, fig. 1645, 1646. 



Gen. 19. PLEUROBRANCHUS, Lam. 



Animal with oval fleshy body, covered by the mantle; foot 

 broad, margined equally ; branchiae on the right side in a 

 canal ; mouth anterior and below, in the form of a proboscis ; 

 two cylindrical tentacula, cleft longitudinally on the external 

 side. Shell internal, dorsal, thin, flattened obliquely. 



VOL. II. E 



