142 



MADRAS FISHERIES BULLETIN 



VOL. XIV, 



Order i.— Opisthobranchiata. 



This order includes the Bubble-shells (BuUidac), the Sea-Hares 

 (Aplysiidac), the Umbrella-shells (Uinhrellidae), one section of the 

 Pteropods and the large and interesting shell-less group of the 

 Nudibranchs. 



The Bubble-shells {BulUdae) are abundant on sandy bottom 

 in shallow water. The swollen oval shells of Bulla ampulla, seem- 

 ingly all " mouth," mottled with pale transparent brownish-red are 

 often thrown ashore at Madras. In life none of the shell is seen, 

 the fleshy lobes of the foot being reflected over the shell both at 

 the sides and behind. In front, the foot, like many other burrowing 

 molluscs, Natica and Oliva for example, forms a stout head-shield — 

 the equivalent in its economy of a plough-share. 



A closely allied species is the little Cylicluia, belonging to the 

 family Scaphandridac. The shell is cylindrical, with a long narrow 

 aperture ; it is not unlike a young Oliva. 



An extremely beautiful animal is the Striped Bubble-shell 

 Hydatifia, belonging to the Aplustridac. The shell has the form of 

 Bulla but is thin and fragile and ornamented with broad spiral 

 black bands on a pale ground. The foot is very broad ; the head 



Vic. 2^1. Striped Bubble-shell {HydatJna circidata\ life appearance showing ihe broad 

 foot and head and ear-like tentacles. (After Adams.) 



disc extremely large. The true tentacles (there are four small 

 labial ones') are wide and ear-shaped and of enormous size, partially 

 covering the shell. The colouring of the foot and the tentacles 

 partakes of the colour scheme of the shell ; it is a wonderful sight 

 to see this creature when crawling in a pool, the shell partly 

 uncovered, the great head with its elephant-ear tentacles stretched 

 forwards and the wide side-folds partly reflected, undulating 

 gracefully over roughnesses of the ground. Hydatina is found 

 but only rarely, on the Ramnad and Tinnevelly coasts. 



