92 AMERICAN JOURNAL 



Adanson's Senegal, p. xv, et. seq., where he will find that the 

 eminent French naturalist, on account of the dire confusion 

 caused in science by the frequent changes of names from their 

 real or fancied inapplicability, was driven to the expedient of 

 inventing "nonsense names," which should have no meaning at 

 all, in order that no one should have an opportunity of changing 

 them on the ground that if one were "thick" another was 

 "thicker," and hence name number one must be discarded ! 



It may not be amiss to add that the younger specimens of A. 

 tenuis before me, such as Prof. Gabb had for description, are 

 decidedly thinner in proportion than those of the other species 

 with which he was acquainted. 



CORBULA (ANISOTHYRIS ?) LED^EFORMIS, n. S. PI. 16, fig. 14, 15. 



Shell somewhat compressed, nearly equivalve. Posterior end 

 much produced ; truncated obliquely at the extremity. Anterior 

 end rather long ; dorsal margin forming an acute angle with the 

 ventral margin ; the last nearly straight. Beaks erect, incon- 

 spicuous, not oblique, slightly curved anteriorly. Teeth in gen- 

 eral as in the other species, slender, small. Externally sculp- 

 tured as in Leda, with a carina extending posteriorly and giving 

 a somewhat double-tube-like appearance to the interior of the 

 siphonal produced extremity. Length -3 in., height 44 in. 



A single specimen of this very distinct species was found in a 

 lump of the agglutinated fossiliferous clay sent by Prof. Orton 

 to the Smithsonian Institution. It is very much longer and 

 more compressed than young specimens of A. carinata, of the 

 same size relatively, and bears no resemblance to any of the 

 others. It is probably young, but not the young of any of the 

 described species.* 



List of the bivalves of the formation. 



Gorhula (Anisothyris) obliqua, Gabb. 



" " tenuis, Gabb. 



" " ovata, Conr. 



" " cuneata, Conr. 



" " erecta, Conr. 



" " carinata, Conr. 



" " ledosformis, Dall. 



Tellina Amazonensis, Gabb. 

 Anodon Batesii, H. Woodward. 



*Mr. Woodward is in error in stating that Ebora " closely resembles 

 Lacuna," which is not a " North American genus " exclusively, nor does 

 it "inhabit brackish water," but is found in the littoral and laminarian 

 zones in salt water. 



