PTEROCERAS. 



specimens; but Swainson, in his Exotic Conehology, has 

 added to the number of recent species, and from our own 

 observations, we are convinced that there are still several 

 others undescribed. The singular digitations of their 

 outer lip and the two canals, spreading and curved in all 

 directions, render these shells very remarkable, and have 

 obtained for them the common appellations of Spiders, 

 Scorpions, &c. A thin horny epidermis coats their gene- 

 rally tuberculated outside in their natural state. One or 

 two species have a single horn projecting between the 

 sinus, near the base of the outer lip and the lower canal. 



We have restored the s at the termination of the 

 generic name, in conformity with the termination of the 

 Greek neuter substantive xs^a? from which it is derived: 

 the Latin adjective specific names should consequently be 

 neuter. 



