OP CONCHOLOGY. 197 



excepting a flatter and smoother upper surface, one whorl less, 

 and a slightly narrower umbilicus. It has, however, no trace of 

 internal teeth, as proved by an immature specimen; the parietal 

 tooth differs in form, and it has two labial teeth situated as in 

 Triodopsis. These connect it with D. Behrii, Gabb, of Guay- 

 mas, which has only five whorls, stronger teeth and a non-pervi- 

 ous umbilicus, showing but IJ whorls. 



The animal does not differ externally from that of Triodopsis 

 loricata from the same region, except that this is black. 



The great altitude at which this is found is remarkable for the 

 genus, as snow falls there several feet deep. It is interesting 

 also in connection with the occurrence of the aWied poli/gi/rella 

 in lat. 47° and alt. about 3000 feet. Its chief distribution is 

 probably more southern, as only two were found, one immature. 



