448 PROCEEDINGS OF THE ACADEMY OP [1881. 



A REVISION OF THE TERTIARY SPECIES OF ARCA OF THE EASTERN 

 AND SOUTHERN UNITED STATES. 



BY ANGELO HEILPRIN. 



In the following enumeration I have reduced all the species to 

 the single genus Area, the various modifications of form and 

 ornamentation not appearing to me to be either sufficiently well 

 marked, or of suflflcient importance, to constitute points for generic 

 subdivision. The Area gigantea Sind A. onochela are forms which 

 would fall in the subgenus Cucullaea. 



The names in parentheses are those under which the species are 

 indicated in the "Smithsonian Check Lists " of 1864 and 1866; 

 they are repeated here merely to facilitate comparisons with those 

 lists, and in no way represent the views of the author on the sub- 

 ject of generic relationship. 



Eocene. 



A. aspera Conr. (Barbatia; Calliarca) Jacksonian. Miss. 



Proc. A. N, S., vii, p. 258, as Navicula. 



A. cucuUoides Conr. (Cucullaroa). Ala. 



Tert. Foss,, 1st ed,, p. 37. 



A. gigantea Conr. (Latiarca). • Md. 



J. A. N. S., vi, p. 227. 



? A. lima Conr. Jacksonian. Tex. 



J. A, N. S., 2d ser., p. 125, as Byssoarca. 

 A. (Byssoarca) Misaissippiensis Conr, J. A. N. S., 2d ser., p. 125 



(young). 

 Cibota Missiasippiensis Gabb. J. A. N. S., iv, 2d ser., p. 387. 



I am somewhat doubtful as to the correct determination of his 

 species by Gabb. 



A. onochela Rogers (Latiarca), Va. 



Trans, Am, Phil, Soc, 1839, p, 372, as CumlloBa. 

 Latiarca idonea Conr. Proc. A, N. S,, 1872, p, 53 (no locality). 



This species appears to be very closely related to, if not identical 

 with the Cueullsea crassatina of Lamarck, from the lower 

 Soissonnais sands of the Paris basin, and possibly also from the 

 British Bognor rock, 



A protraota Rogers (Ana''ara). Va. 



Trans. Am, Phil. Soc, new ser,, v, p. 332. 



