^sshninki Gray ana. 4!29 



fies the conclusions formed tVoni a careful examination. 



I speak with greaier caution on the point in deference to Mr. Lowe's 

 experiments on an animal evidently congeneric: and I do not advert to 

 them as in the present Number some observations are made upon them, 

 in consequence of a communication which was transmitted to him on the 

 subject. 



On seeing the animal I was immediately struck wiih its resemblance to 

 tliat of Physa or rather Aplexa. On mentioning this to Mr. G. B. 

 Sowerby, he informed me that he has some fluviatile Limnatdcs from 

 South America which tend lo confirm, my suspicion. On the whole, I 

 think that there can be little doubt that it is most nearly allied to ./Iphxa; 

 and, as it appears to me, an object of some interest as connecting the 

 LimnceidcB with Car\jchium, Auricula, &c. 



ASSIMINIA GrAYANA. 



Foot broadly obovate, obtuse, composed evidently of two distinct 

 laminae, the lower projecting beyond the upper, and separated from it 

 by an accurately defined line; above fuscous, beneath olivaceous shaded 

 with cinereous. 



Tentacula very short and obtuse, fuscous, eyes at their tips. 



Mwzz/e porrected, not truly proboscidiform, deeply notched in front, 

 fuscous, strongly annulated ; the edge of the lip paler: on each side is 

 a groove running backwards from the base of the tentacula. 



Mantle open behind. 



FcBces elliptical (as in Cyclostoma). 



Operculum corneous, ovate, spirally striated. 



The most remarkable circumstance in this animal is the position of 

 the eyes, at the tip of the tentacula, as in He//x and its allies, and not at 

 the base. It would appear as if there were in reality no tentacula and 

 only the tubercle common to many Mollusca at the base of the tentacula, 

 a little more developed than usual. The shell is so like that of some 

 species of Rissoa that it is quite surprising that in Dr. Fleming's British 

 Animals and Mr. Jeffrey's paper in the Linnean Transactions it should 

 be placed in or close to the genus Limncea. Dr. Leach seems to have 

 formed his conclusions from an actual inspection of the animal, and con- 



