64 ANATINID^. 



Ill the course of the reformations recently made in the indefinite 

 genus Anatina of Lamarck, this shell has passed under several ge- 

 neric appellations. A genus was instituted by Leach, to receive the 

 old Mya Norvegica, which he called Mogdala, and, still later, Scac- 

 chi has named it Pandorina. Perhaps I may be censured for 

 breaking, in this instance, the salutary rule, that the oldest pub- 

 lished name should take precedence of all others. The genus Ly- 

 onsia certainly preceded that of Osteodcsma, and so, I think, did 

 Mngdala. But the name Osteodesma is so well chosen, and is so 

 well made known in the recent edition of Lamarck's work, being, 

 moreover, the type of the natural family Octcodcsmacea^ that I can- 

 not refrain from giving it the preference. [More mature considera- 

 tion has induced me to conform to the general consent of conchol- 

 ogists and adopt the older name. Magdala was only a manuscript 

 name until 1827. 



Lyonsia hyalina. 



Pig. 31. 



Shell sub-ovate, fragile, pearly, translucent, inequipartite ; elongated, com- 

 pressed, and truncated posteriorly; covered with radiating wrinkles; ossiculum a 

 truncated wedge. 



Mya hyalina, Conrad, Journ. Acad. Nat. Sc. vi. 261, pi. 11, fig. 12. 



Lyonsia hyalina, Conrad, Amer. Marine Conch. 51, pi. 11. fig. 2. — Stimpson, Shells of 



New England, 23 ; Inv. Gr. Manan, 21. 

 Osteodesma hyalina, Coutiiouy, Best. Journ. Nat. Hist. ii. 166. — De Kay, Nat. Hist. 



New York, 234, pi. 33, figs. 311, A, B. — Gould, Inv. Mass. 1st ed. 46.— 



MiGHELS. Bost. Journ. Nat. Hist. iv. 315. 



Shell elongated, sub-ovate, thin, fragile, pearly, translucent, in- 

 equipartite, the posterior part much the longer, nar- 

 Fig. 380. rowed, closely compressed at the end, but slightly 



truncated, so as to gape a little ; hinge margin a 

 straight line and compressed ; the remaining out- 

 IThyaUna. ^^^^^ rcgularly rounded ; beaks prominent, inclining 



forwards ; region of the beaks tumid and smootli ; 

 a broad marginal portion is covered by a thin membranous e|iider- 

 mis projecting beyond the edge, and wrought into regular wrin- 

 kles, radiating from the beaks ; these wrinkles are minutely fringed 

 so as to entangle grains of sand, by which the surface is sometimes 

 entirely coated. The hinge consists of a delicate ledge, running 

 from the beak obliquely downward and backward, serving for the 

 attachment of a ligament, which is also attached to the edge of 



