GASTEROPODA. 117 



cular and somewhat irregular; slightly convex above, with 

 the vertex towards the centre ; internal cavity but slightly 

 hollowed, with a coloured, callous disk, impressed in the 

 centre. 



Umbrella Indica.—TsE Indian Umbrella. Plate XIV. 

 fig. 24. Ovate, slightly convex above; the vertex towards 

 the centre; whitish, with the summit yellow; longitudinally 

 striated, and concentrically wrinkled ; inside with radiating 

 striae. Four inches in diameter. Inhabits the Indian seas. 



Geraws 23.— PLEUROBRANCHUS. -Zamarc^i. 



Generic Character. — Body creeping, fleshy; mantle and 

 foot expanded ; branchiae placed on the right side ; cloak 

 enveloping the shell; neck short, contracted in some spe- 

 cies, with an emarginate front, exhibiting the commence- 

 ment of the inferior tentacula, the upper ones tubular and 

 hollow; branchiae at the edge of the dorsal plait, in front 

 of which are the generative and anal orifices ; mouth pro- 

 vided with a short retractile proboscis. Shell dorsal and 

 internal, thin, flat, and obliquely oval. 



Pleurohranchus plumula. — The Plumed Pleurobran- 

 CHUS. Plate XIV. fig. 14. Ovato-oblong, depressed, 

 pellucid, yellowish-white, concentrically wrinkled, almost 

 entirely open, rounded, and convoluted ; the vertex with a 

 single turn. Half an inch long. Inhabits the Devonshire 

 coast. 



TRIBE VI. PHYLLIDIACEA. 



The branchiae situated beneath the margin of the mantle 

 in a longitudinal series around the body. Animals respiring 

 water. 



Genus 24 F ATELL A.— Linnceus. 



Generic Character. — Body completely covered by the 

 shell; head with two pointed tentacula, having the eyes 

 situated at their exterior base; branchiae placed in a series 



