194 



a tubular perforation) cannot, howeverj be placed in any 

 other genus with fo much propriety, Poffibly many of 

 the minute fpecies of Nautili, would be found to be va- 

 rious in the ftrufture of xhtfepta, and fome not poirefled 

 of tubular apertures, could we dilTefcl. them with perfpi- 

 cuity : fo that the formation of the aperture in ihefcpta, 

 had better be confidered (as Mr. Lightfoot jufUy ob- 

 ferves) a fpecific, rather than a generic, charatler. 



This may, therefore, be accounted as the only fpecies 

 of frefli water Nautilus hitherto noticed. 



The animal is an aquatic Liniax, or Slug; it has two 

 very long, (lender, filiform tentacula : at the bafe of 

 which are two eyes, placed on the head, not on their 

 fummits, and retratlile, as in thofe of the land kind. 



"When the animal extends itfelf, the head, tail, and 

 part of the body, are protruded through the triradiated 

 aperture, each at a feparate part ; the head at that of the 

 middle ray : after it is dead, it contrafts within the two 

 omer Jepta, but never as we could obferve, beyond the 

 third; which makes that divifion always obfcure. 



Mr. Walker fpeaks of its being found on flag=;, in 

 Hernhill brooks, in Kent: it is alfo met with about 

 Sandwich, from which place we have received it from 

 Mr. Boys. 



Mr. Light- 



