INVERTEBRATE rALJSONTOLOGY. 113 



Complanaria, Swainson (1840), M.alac, 280 and 382.— H. aud A. Adams (1857), Gen. Eec. Moll., II, 



. r >00 (as a subgenus under Baphia). 

 Unionopsin, Swaiuson (1840), Malac, 264 aud 382. 

 Calceola, Swainson (1840), ih.. 280 and 382.— H. and A. Adams (1857), Gen. Rec. Moll. II, 500 (as 



a subgenus under Baphia ; not Calceola, Lam., 1790). 

 * Baphia, II. and A. Adams (1857), Gen. Kee. Moll. II, 500 (not Meuschen, 1787?). 



Elijm. — Margarita, a pearl. 

 Type. — Mija margarittfera, Liuu. 



Shell varying in form from transversely elongate-snbelliptic, to shorter 

 oval, snbtrigonal, subrhombic, &c. ; surface smooth or plicated, and covered 

 with an olivaceous epidermis. Hinge with anterior tooth single and erect in 

 the right valve, and double in the left ; or with two (rarely three) anterior 

 teeth, sometimes represented by irregular tubercles ; posterior teeth wanting, 

 or occasionally represented by obscure, irregular grooves. 



The following sections of this group have been admitted by H. and A. 

 Adams, Chenu, and some others : 



1. margaritana, Schum. (typical). 



Shell transversely elongate-snbelliptic ; anterior teeth single in 

 right valve and double in left ; posterior teeth wanting. — (Type as 

 already stated.) 



2. ALASMODONTA, Say. 



Shell oval, subtrigonal or subtrapezoidal ; beaks large and promi- 

 nent ; surface smooth ; hinge with two cardinal teeth. — Margaritana 

 Curreyana, Lea. 



3 COMPLANARIA, SwaillSOll. 



Shell oblong, subrhombic, &c. ; valves connate, with a smooth or 

 plicated surface; anterior teeth two or three; lateral represented by 

 irregular grooves. — M. arcula, Lea. 



4. unionopsis, Swaiuson (— Calceola, Swainson, 1840; not Lam., 1799). 



Shell ovate, smooth ; anterior teeth two, irregular, or represented 

 by tubercles and undulations. — M. calceola. Lea. 



These sections are probably hardly all entitled to rank as subgenera. 

 Indeed, the whole taken together, are regarded by Dr. Lea and some other 

 high authorities, who have given much attention to the study of the Unionida>., 



* The name Baphia, Meuschen, 1787, according to Herrmannseu, was proposed for a group including 

 species of Unio, Psamobia, Vuhella, Mya, and Anomia. If so, I should think it could not be properly inado 

 to replace Margaritana, SVhum. 



15 n 



