68 i^i''- AdamsV Spccijic CbiVticlcys of fme minute Shells 



is lefs than the anterior extremity of the bod3\ to which it is con- 

 iie61ed by the membranaceous covering of the head forming a neck : 

 on the top are fituated twowhite cyhndrical tcntaculci, capable of being 

 elevated or depreflcd 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 ftrudlure 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 procelTes to the external coat in the articulations, for the 

 purpole of keeping this long inteftine fteady : a fimilar contrivance 

 is obl'ervable 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 colle6lion, 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 diftina genus ; to 

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

 have jriven the title of Derris. 



to' 



E X P L. OF TAB. 13. 



Fig. I. Derris fanguinea of the natural fize. 

 2. The head magnified. 

 3, 4. Buccinum breve. 

 5, 6. Buccinum minutum. 



Fig. 7, 8. 



