ASSIMINEA. 101 



The Nerita Syncera Hepatica of Gray, so named but 

 not described in vol. xv. of the ' London Medical Re- 

 pository/ The reason which he gave for proposing a 

 trinomial system is rather curious, i. e. " because I think 

 that it is easier to recollect Umax arion hortensis than 

 arion hortensis alone, as genera are now become so 

 numerous, that naturalists really want something to let 

 them know to what part of natural history they belong." 

 Dr. Gray afterwards published the specific name as 

 Grayiana ; but that may have been a misprint. 



2. A. LITTORI'NA*, Delle Chiaje. 



Helix littorina, D. Ch. Mem. An. s. Vert. Nap. iii. p. 215, t. 49. f. 36- 

 38. Bissoa littorea, P. & H. iii. p. 132, pi. Ixxxi. f. 6, 7, and iv. 

 (App.) p. 265, and (animal) pi. MM. f. 3. 



BODY white, with a faint tinge of yellow, and of a frosty or 

 reticulated texture : mantle rather thick, lining the mouth of 

 the shell : snout broad, thin, and wedge-shaped, slightly bi- 

 lobed or nicked in front : tentacles very short, bat-shaped and 

 flattened at the sides: eyes comparatively large and black; 

 viewed sideways they seem placed near the tips of the tentacles, 

 but not quite at the extremities ; viewed from above they ap- 

 pear terminal : foot broadly oval, squarish in front, and rounded 

 behind ; it is somewhat constricted in the middle ; and when 

 the animal is crawling, it is divided into two parts, each of 

 which advances in turn by a wave-like motion : respiratory 

 orifice round and large, on the right-hand side. In one in- 

 dividual which I examined the heart beat with 90 pulsations 

 in a minute ; the pulsations were not continuous, but occasion- 

 ally interrupted. 



SHELL globosely conical, solid for its size, semitransparent, 

 and glossy: sculpture, indistinct and microscopic, close-set, 

 spiral striae, besides equally minute and numerous lines of 

 growth : colour brownish-yellow or amber, sometimes yellowish- 

 white or whitish : spire short, and having a very blunt point : 

 whorls 4, rather convex, rapidly enlarging ; the last occupies 

 three-fourths of the shell; the first is mammillar; suture deepish, 



* Derived from littus or litus,t\\e shore. 



