Zoological Society, 416 



With regard to Rostellaria rectirostris, or more properly recti^ 

 rostrata, I have a few words to say before I conclude this somewhat 

 desultory communication. 



The animal of this genus is exactly like that of Stromhus. The 

 body is subcylindrical, marbled with rich brown on the outer side, 

 and white on the inner and front side. The trunk is subcylindrical, 

 and annulated with a central broad line of deep bronze-black. The 

 margins yellow with a narrow vermilion line externally. The eyes 

 are on long cylindrical peduncles, of a deep blue with a black pupil. 

 The tentacula are subulate, elongate, arising from the peduncle rather 

 below the eye. The foot is narrow, rather dilated in front and small 

 behind. The operculum is ovate, triangular, annular, semi-transpa- 

 rent and horny. Living in black muddy sand in thirty-one and a 

 half fathoms water. The specimen I figured was dredged on the 

 coast of Borneo. 



Rostellaria has all the habits of the StromhidcD, progressing by 

 means of its powerful and elastic foot, which it places imder the shell 

 in a bent position, when suddenly by a muscular effort it straightens 

 that organ and rolls and leaps over and over. It is however far more 

 timid and suspicious than Stromhus, which has a bold disposition. 



The animal of the genus Stilifer, which I found living on the body 

 of a starfish (Asterias) on the coast of Borneo, had two elongate 

 subulate tentacles, with the eyes sessile near the outer side of their 

 base, and a small rounded head. The mantle is entirely enclosed and 

 covered by the thin shell, and the foot is narrow, slender, very much 

 produced beyond the head in front and scarcely extended at all be- 

 hind. 



The animal of this genus was described and figured in Mr. Sower- 

 by's * Genera of Shells ' from a specimen in spirits brought home by 

 Mr. Cuming, where the fleshy part enveloping the shell in its con- 

 tracted state was considered as the mantle. 



Mr. Gray, in the Synopsis before referred to (ed. 1842, p. 60), 

 from the examination of these figures, placed the genus in the family 

 of NaticidcB, and observes that " what has been called the enlarged 

 mantle appears like the foot ;" and the above description of the ani- 

 mal shows the accuracy of Mr. Gray's conclusion, both as to the 

 proper nature of the fleshy part and the position of the genus in the 

 system. 



In the shallow pools left by the receding tide on the shore of 

 Koo-Kian-San, one of the Maiacoshima group of islands, I discovered 

 a large species of Dorididce, which appears to be the type of a new 

 genus, diifering from all the other genera of the family in having the 

 vent, and the gills which are extruded from it, situated beneath the 

 edge of the mantle, which latter is extended beyond the circum- 

 ference of the foot, while in all the other genera, as far as I am aware 

 of, the vent and gills are situated on the mantle itself. This genus 

 may be called Hypobranchijsa*. 



* virh {sub), ppayx'ieta (branchiis preedita). The specific name might be " de- 

 pressa," from its flattened appearance. 



