226 COIHGRYUA—DITHYRA. 50. 



removed without destructive violence. And this attachment is 

 effected, either by a solid elliptic testaceous appendage, which pier- 

 ces and fits the perforation in the lesser or under valve, and is 

 dilated and firmly adhesive at its base, as is represented in our plate 

 17, fig. 10 ; or is a mere tough tendinous plug, as is the case with 

 most of those which are attached to Fuci. 



The great irregularity of figure and substance in many of the 

 species, occasions such difficulty of discrimination, that we do not 

 think the genus has as yet been well understood, or clearly elucida- 

 ted. 



Montagu confines the British species to Anomia Ejjhippium, A. 

 undulata, A. aculeata, and A. cylindrica : but our own researches, 

 chiefly among the rocky shores of Devonshire, have led us to the 

 belief, that much curious matter yet remains for further develope- 

 ment, and a more accurate investigation of this hitherto obscure 

 genus : and we submit our own conclusions, respecting the determi- 

 nation of species, to the correction of better experience. 



In our figures, all drawn from specimens taken alive, it has been 

 our wish to present them in their less known stages of growth, or 

 to exhibit their remote and more dissimilar ajjpearances and allian- 

 ces. And it may be proper to remark, that in our specific descrip- 

 tion, we consider the lesser valve, or that which is perforated, as 

 the under one. 



electrica. Anomia testd suborbiculari, subundatd, pellucidd, succined. 



Shell somewhat orbicular, with the surface a little undulate, trans- 

 parent, and amber-color. 



