192 PNEUMONOBRANCHIATA. 



tooth ; the outer margin thin, not reflected, nor form- 

 ing an umbilicus. 



This common species was first noticed as British 

 by Mr. Boys ( fig. 61.), and his figure 89. appears to 

 represent the young shell. It is very common, six or 

 eight inches deep in the ground, in Yorkshire, on the 

 tops of gravel pits, and in Saxon coffins. 



The animal, from the transparency of the shell, 

 may be seen to dilate and contract its respiratory 

 cavity through the shell. This motion has been 

 taken for the beating of the heart ; it is irregular 

 sometimes fast and sometimes slow. 



The eggs are large compared to the size of the 

 shell ; and this explains the bluntness of the apex, 

 arising from the large size of the body of the animal, 

 on which the shell is formed before it is hatched. 



Pfeiffer, in his delineation of this shell (part 1. 

 tab. 3. fig. 8, 9.), has erroneously exhibited the aper- 

 ture as quite rounded at the base, without the least 

 truncation of the pillar, thereby fixing it in the 

 genus Bidimus. 



11. Pupa L«w. (Chrysalis Shell.) 



Animal like Bulimus, with four club-shaped tentacles, 

 the lower pair short, small, and with a cylindrical 

 abruptly obtuse shell, with close pressed, gra- 

 dually enlarging whorls; the mouth semi-oval, 

 mostly toothed internally ; peristome renexed, and 

 interrupted behind. 



The young shells have a flattened front to the 

 whorls, and a squarish mouth, so that they were mis- 

 taken by some of the older conchologists for Trochi; 

 the older whorls are more convex and rounded in 



