196 Mr. A. Adams cm the Animals of some Mollusca. 



XXIII, — On the Animal o/iMycseus and some other Cyclaphoroid 

 Genera. By Arthur Adams^ F.L.S. &c. 

 1. Alyc^us. 

 The animal of a species of Alycceus, from the island of Mah- 

 lu-San, or Port Hamilton^ in the Korean Archipelago, is semi- 

 opake white, with a pale oi'ange blotch on the upper part of the 

 rostrum, which is caused by the buccal mass shining through 

 the transparent skin. The tentacles are short and gradually 

 tapering ; the eyes small, black, and basal ; the muzzle is rather 

 narrow, annulate, and strongly bilobed at the end. The flat 

 operculum is carried on the dorsum of the foot, midway between 

 the shell and the end of the tail. The chief peculiarity, however, 

 is the great anterior development of the body, which, when the 

 animal is on the move, is considerably extended, giving it in 

 this respect some resemblance to a Helicina. 



2. Hydrocena. 



A species, from the island of Awa Sima, one of the Japa- 

 nese Archipelago, is of a pale brown colour. The muzzle is 

 broad and transversely strongly wrinkled; the tentacles are 

 cylindrical and obtuse at the ends; the eyes are large, black, 

 prominent, and basal ; the foot is short, with parallel sides, and 

 obtuse and rounded behind. The operculum is on the back of 

 the foot, close to the body of the animal. 



3. Pterocyclos. 



The colour of a species which I discovered in the island 

 of Tsu-Sima, in the Korea Strait, is blackish brown, with a 

 lighter streak down the sides of the foot ; the tentacles and end 

 of the muzzle are darker than the rest of the head. The muzzle 

 is broad, and finely wrinkled across as in other genera of Cyclo- 

 phoridse ; the eyes are not prominent, but small and basal ; and 

 the foot is long, narrow, and tapering behind. 



The chief peculiarity, however, is in the position of the oper- 

 culum, which, one would imagine, would be carried on the ex- 

 treme end of the tail, free from the shell. It is, however, borne 

 close to the body, and, during progression, is received into the 

 deep funnel-shaped umbilicus, where it is concealed and out of 

 the way. The locomotive powers are limited; and the animal is 

 easily alarmed, when it withdraws far into the shell, the apex of 

 the conical operculum being just level with the peritreme. I 

 found this species in rocky places where the vegetation was 

 abundant, crawling among dead leaves at the roots of trees. 



4. PUPINELLA. 



A little species which I discovered at Chosan, in the Ko- 



