Ton d-sn ails 307 



formed by the union of the front edge of the mantle 

 with the neck of the snail. The .sexes are united in 

 each individual ; the shell may be developed 

 or not ; and there is no operculum. The order ^ 

 is divided into two sub-orders — Basommato- >P 

 phora, or those that bear their eyes at the Least 



' , , , 1 ciL ^ L Herald-shell 



base of the upper tentacles ; btylommato- (enlarged) 

 phora, or those whose eyes are carried at 

 the tips of the upper tentacles. There are other 

 differences : for the moment we will be content with 

 stating the characters of the first sub-order. The 

 tentacles cannot be retracted, the teeth are in many 

 rows across a radula, there is always a shell and it 

 is always external. The genus Carychium is in- 

 cluded in the family Auriculidce, whose members 

 have conical shells, and as a rule they increase its 

 roominess not only by adding new matter to the lip, 

 but also by absorbing the internal partitions, and to 

 make up for the want of an operculum they develop 

 the tooth-like processes across the mouth of the shell 

 shown in the figure above. The breathing organ is 

 developed into a true lung, for the air-chamber is 

 lined with delicate vessels through whose tissues the 

 circulating blood can absorb oxygen. 



0. minimum lias a shell about one-eighth of an 

 inch in length ; but in spite of its small size botli 

 shell and animal are beautiful. The latter is trans- 

 parent, with a triangular snout, thick tentacles, and 

 prominent black eyes. The shell is almost spindle- 

 shaped, transparent wliite, glossy, with an ear-shaped 

 mouth obstructed by two strong teeth. The umbilicus 

 is represented by an oblique slit. It is fond of damp 

 places, and must be sought under stones or felled 



