110 Mr. A . Adams on the Animals of certain Mollusca. 



Hydrobia and Amnicola. The rostrum is large, thick, and 

 annulated, and, when the animal is crawling, is extended beyond 

 the fore part of the foot. The tentacles are strong and subulate, 

 and the eyes are large, prominent, and black, on the outer side 

 of their bases. The foot is oblong and moderate, and strongly 

 auriculate on each side in front; the sole and operculigerous 

 lobe are simple. The operculum is subspiral ; it is thick and 

 shelly, and is composed of three rapidly enlarging whorls. 



I discovered the species S. punctostriata, A. Adams, crawling 

 slowly on the moist soil at the roots of grass, between high- and 

 low- water marks, on the banks of the river Yang-tse. It appears 

 to be very sluggish and inactive in its habits. 



In Borneo I found another species, S. olivacea, A. Adams, 

 adhering to the under surface of dead leaves, and crawling about 

 the soft mud by the sides of ponds. The nature of the opercu- 

 lum places this genus in the same group as Hydrobia, and not 

 in the family Viviparidse, where my brother and myself have 

 arranged it, judging from the similarity of the shell to that of 

 Bithynia. 



Associated with these little Stenothyra, in considerable num- 

 bers, was a species of Assiminia, of large size, and, I believe, at 

 present unnamed, if it be not A. Francisca of Gray, from India. 



The animal of this species progresses very much in the same 

 manner as Truncatella, by means of its broad muzzle and short 

 rounded foot. Short cylindric peduncles arise from swollen 

 conical bases, wide apart on the upper surface of a flattened 

 head, beyond which a dilated muzzle, bilobed at the end and 

 ringed with black-brown lines, extends far beyond the front 

 edge of the foot. A line is conspicuous on the sides of the 

 peduncles, indicating the union of the tentacles and eye-pedicels. 

 The eye, with a pale iris and a large black pupil, is placed at the 

 end of an oblong bulb. The sides of the foot are marked with 

 lateral, wavy, light brown dotted lines ; the sole is ovate, ob- 

 tuse at both ends, and of a dull dirty white. The operculum is 

 thin, horny, subspiral, and rather pointed behind. 



Genus Umbonium, Link. 



At Hakodadi I had an opportunity of examining the animal 

 of Umbonium giganteum of Lesson, which occurs along the sands 

 of the bay, but is extremely difficult to obtain alive without 

 dredging for it. I found Dr. Gray's account of the creature to 

 be very correct in the main ; but I imagine the simplest view of 

 the nature of the veil is to consider it a dilatation of the left 

 tentacle. The lateral membrane in this species has four fila- 

 ments on each side, whereas in U. vestiarium, Linn. (Rotella lineo- 

 lata, Lam.), Dr. Gray mentions only three. The eye-peduncles 



