3IAEGAEITAXA, 



G7 



IV. SUBGENUS MARGARITANA. 1 



PS 



< a 



TRIANGULAR. 



*complanata. Bar. Lea. 



Alas, complanata. Bar. Hild. Soiv. 

 Symph. complanata. Lea. Sh. <£■ Eat. 

 TJnio complanata. Desk. Hun. 

 My a complanata. Bat. 



QUADRATE. 



*confragosa. Say. Lea. 

 Alas, confrayosa. Say. 

 Unto confrayosa. Desk. Han. 



TRIANGULAR. 

 *arcula. Lea. 



Alasmodonta arcula. 



Chenu. Han. 



oains. Stimp- 



OBLONG. 



TJnio marginatus. Reeve. Han. 

 Mya regulosa. Wood. Han. 

 Mya rugosa. Eat. 

 Alas, corruyata. Dehay. 

 Vignouana. Bern. 



*rugosa. 4 Lea. Kirtl. 



Alas, rugosa. Bar. Sh. & Eat. Hild. 



Adams. Dehay. 

 Alas, abducta. Say. 

 Complanaria rugosa. Swc 



son. (Agass. MSS.) 

 TJnio rugosus. Chenu. Hun. 



| OBLONG. 



3 1 *Gesnerii. Lea. 



TRIANGULAR. 



*deltoidea. Lea. 



Alasmodonta deltoidea. Chenu. Han. 



*minor. Lea. 



Alasmodonta minor. Chenu. 



1 The genus Margaritana was proposed by Schumacher, in his Essai d 7 un Nouveau Systeme des 

 Habitations des Vers Testaces, published in 1817, for the Mya margaritifera, Lin. (Unio elongata, Lam. 

 and Alasmodonta arcuata, Bar.). Mr. Say, in 1818, proposed to establish this same division under the 

 generic name of Alasmodonta. The Danish zoologist, having priority of date, must have his name pre- 

 ferred. Mr. Gray, iu his Genera, adopts Margaritana, but he cites Baphia, Gevers, in 1787. H. and A. 

 Adams, in Genera of Bee. Mol., give Baphia preference, and cite Meuchen, in Museum Geversianum, 

 1787, as having priority, which I think is correct; and they make the following subgenera — Alasmodonta, 

 Sa}', Complanaria, Swain., Calceola, Swain. 



2 This species has a very wide geographical distribution. In the St. Lawrence and in the Northern 

 States, it is of ordinary size as it is in the Middle States ; but in Ohio it is found large and thick, and 

 very perfectly developed. In South Carolina, Georgia, and Tennessee, it is smaller; and in Kansas, in 

 Verdigris River, it is very much like those in Pennsylvania. 



3 Several specimens of fine marginata have been sent to me from the west, marked Alas, truncata, 

 Say, being one of his unpublished names, but specimens given by him to various conchologists under 

 that name. I have never considered it distinct from the marginata of the eastern rivers, although it is 

 generally larger and of finer color in the exterior. 



4 I found the oviducts of M. rugosa fully charged on the 20th May. 



