23 



Haviug aii opportunity of examming both iii a living statė in the 

 summer of 1832, I was surprised to find maiiifest indications that 

 both were pulmoniferous, which were confirmed on a minute inspec- 

 tion of the internal structure, as far as perhaps could be expected in 

 such.small animals. I was enabled in the former to trace distinctly 

 the course of the vessels, and was decidedly of opinion that the hings 

 were coustructed for the breathing of air unmixed with water. In 

 the other case I was not so successful, though the ntmost pains were 

 taken ; but as the animal is only half the size, the difficulty was much 

 increased. I am enabled, however, to assert, that I could detect 

 nothing likę branchise ; and v/hat is more to the point, that the vault 

 of the cavity of respiration was traversed by a multitude of minute 

 vessels all tending one way towards a large vessel running down in 

 the direction of the heart, which is exactly the structure in pulmo- 

 niferous MoUusca. This, perhaps, will be esteemed as decisive when 

 the external characters of the animal are taken into consideration." 



" ASSIMINIA GrAYANA. 



" Foot broadly obovate, obtuse, composed evidently of two distinct 

 iaminse, 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 the tips. Muzzle 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. Fseces elliptical (as in Ci/clo- 

 stoma). Operculum corneous, ovate, spirally striated. The most 

 remarkable circumstance in this animal is the position of the eyes, 

 at the tips of the tentacula, as in Helix 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 MoUusca at the base of the 

 tentacula a little more developed than usual. The shell is so likę 

 that of some species of Rissoa, that it is quite surprising that in 

 Dr, Fleming's ' British Animals,' and in Mr. Jeffreys' 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 iuspection of the animal, and consequently made a distinct 

 genus for its reception. In many points the animal resembles very 

 much that of Cyclostoma, and is perhaps a step nearer than that and 

 Helicina, which have the mantle open behind to the pectinifera. 

 Its nearest ally, however, amongst the pectiniferous MoUusca I 

 should conceive not to be Rissoa. 



" The animal and shell are figured in Forbes and Hanley's ' British 

 MoUusca,' iii. 70, t. 71. f. 3, 4, and t. H.H. f. 6. 



" Mr. Benson, at page 463 of the šame volume of the Zool. Joum., 

 has given the followuig description of the animal of Assiminia fas- 

 ciata {Turbo Francesii, Gray, in Wood's Supplement, t. 6. f. 28) : 

 — " Animal : Head with only two short, thick, subcylindrical ten- 

 tacula, with the percipient points placed at their summits. Snout, 

 hke that of Paludina, transversely corrugated and bilobed, or rather 



