214 



This, therefore, feems to be the link between the true 

 viollufca animals, and the tejlacea: and it is probable fu- 

 ture refearches may difcover, that many which have hither- 

 to been confidered as belonging to the mollvfca tribe, are 

 really tejlaceous, upon difleclion. 



6. 

 Plumula. B. with an ovate-oblong, depreffed, pellucid, thin fhell. 



Tab. 15. f. 9. of a yellowifh-white colour, tinged with brown at one end ; 

 the other end minutely convoluted on the back, or upper 

 part, like the Bulla Haliotoidea, but much fmaller; the 

 convolution makes one turn ; it is flrongly wrinkled con- 

 centrically for fo delicate a fliell, and is pofTefTed of two 

 or three ray-like indentations, running from the margin 

 towards the a/'^x. Theinfide, aswellasthe outfide, isfome- 

 what gloffy and wrinkled; the aperture extends the whole 

 of the fliell, like the B. aperta: the pillar lip is flightly 

 turned inward, to form the fmall depreffed volution ; but 

 the aid of a glafs is requifite to difcover the formation of 

 this part. Length half an inch ; breadth near a quarter. 



This is another of thofe fingular mollufca animals, with 

 a concealed fhell under the flcin upon the back : its (hape 

 is fub-oval, but variable; the Suftentaculum is large, and 

 ovate, but ufually in folds at the edges : the front is gene- 

 rally roundifh ; the body is fmall, covered with a broad, 

 thin, fuborbicular, reticulated membrane, variable in 

 fliape, frequently turning back at the margin : the head, 

 which is mod times concealed under the membrane or 

 fhield, is furnifhed with two broad tentacula, which are 



fometimes 



