340 Rev. Mr. Lowe's Desanption of the 



the shell itself, where it is exposed on the left side of the animal. 

 Through this part also, when the animal is at rest, may be seen, on the 

 left side, beneath the whitish organ just mentioned, a strong and regular 

 pulsation and motion of systole and diastole, or of alternate contraction 

 and dilatation. The part in which this takes place is the pericardium : 

 and that in which the vessels above described are perceptible is the pul- 

 monary cavity. This last occupies, when the animal is crawling, the 

 larger portion of the last volution of the shell, extending about half way 

 backwards from the outer lip. The pericardium is at the back of the 

 pulmonary cavity and on the left side; the remainder of the first volution 

 backwards, and the spire of the shell, are occupied by the liver which is of 

 a dark brown colour, with a few fine milky veins interspersed through 

 its substance. 



The posterior extremity is acuminated, pointed, triangular when tha 

 animal is at rest, elongated when in motion, convex and carinated down the 

 middle. The keel is formed by the opposition of the two lips of skin which 

 form the edges of the bed in which the posterior part of the shell is sunk; 

 and which thus, while giving the appearance of a keel, form in reality a 

 close channel or groove. This is continued a part of the way down, but 

 not to the extremity. The oblique grooves before mentioned on these 

 lips of skin are continued on each side to the extremity of the tail, 

 dividing it into compartments on each side. There is no appearance of 

 a terminal mucous pore. 



Head, cheeks, and mouth externally as in Helix. 



The tentacula are four, cylindric, retractile, with black points at the tips 

 only of the upper and longest pair. 



The orifice of the organs of generation is close beneath and a little be- 

 hind the base of the right tentaculiim, on a line with the shorter pair of 

 tentacula. 



Foot as in Umax or Helix; narrow, elongate. 



The shell is spiral, of three or four volutions, extremely thin and fra- 

 gile, pellucid, very glossy and shining, of a bright amber yellow with ge- 

 nerally a greenish tinge, much depressed or flattened, ear-shaped, the last 

 volution vastly large ; the breadth, in the usual acceptation, (or here more 

 properly length in respect to the position of the shell on the animal) 

 exceeding considerably another diameter at right angles to it, and equal- 



