68 Mr. AdamsV Specific Characters qfjbme nimute Shells 



is lefs than the anterior extremity of the body, to which it is con- 

 needed by the membranaceous covering of the head forming a neck : 

 on the top are fituated two white cylindrical tentacula, capable of being 

 elevated or deprefied at pleafure : the mouth confifts of two lips ; 

 the lower one ftraight and fixed, the upper one hooked and move- 

 able : when the animal is at reft it is open, but is frequently clofed 

 with wonderful quicknefs, probably to fecure the animalcula on 

 which it may be prefumed to feed. 



The internal ftructure is compofed of a fimple alimentary canal, 

 fomewhat larger in the joints ; this increafe of fize in thofe particu- 

 lar parts originates, as I conceive, in its being attached by tranf- 

 verfe proceiTes to the external coat in the articulations, for the 

 purpofe of keeping this long inteftine fteady : a fimilar contrivance 

 is obfervable in the genus Echinus ; it is capable of partial dilatation 

 between the joints only, which is an additional proof of its being 

 faftened there. The animal moves by an undulatory motion of 

 the whole body. 



Though the liberality of Sir Jofeph Banks has enabled me to 

 confult his extenfive collection, I have not been able to meet with 

 any author who has defcribed a marine animal refembling this^ 

 In this cafe it feemed moft eligible to make it a diftincl: genus ; to 

 which, from the truly membranaceous fubftance of this fpecies, I 

 have given the title of Tkfris^ 



E X P L. of TAB. 13, 



Fig. 1. Derris fanguinea of the natural fize. 

 2. The head magnified. 

 3, 4. Buccinum breve. 

 5, 6. Buccinum minutum. 



Fig. 7, 8. 



