THE NAUTILUS. 33 



mentina. Except eventually for that, U. crassus cannot be regarded 

 as a synonym of the species named, and it would be best to drop the 

 name. 



Unio plicata. Unfortunately, the author failed to cite the dimen- 

 sions. To judge from the description and also the locality, Lake 

 Erie, it seems that not the large " typical " plicata of e. g., the Mis- 

 sissippi and Ohio rivers was understood, but the well marked 

 " variety," known also e. g., from the Kankakee river. 



U. ochraceus. Description and figure evidently are drawn from a 

 young, resp. adolescent specimen, two or three years old, and the 

 differences as pointed out from cariosus (the figure represents a 

 mature female) are mostly due to this fact. 



Oyclas similis. The description shows decidedly that the mussel 

 understood is not what has been taken for Sphserium simile, resp. 

 G. sulcatum Lam.; the size given is: long. 10, alt. 8.75 mill. Any 

 specimen of G. sulcatum, 10 mill, long, is rather young, not " sub- 

 orbicular," but elongate, and little inflated. The figure also, how- 

 ever imperfect it may be, cannot represent a G. sulcatum. The 

 species described seems to be either G.striatinum Lam, or stamineum 

 Con., probably the former. The statement that "a specimen 

 measured in length 1 nearly three-fifths of an inch," makes it prob- 

 able that a G. sulcatum was mixed in. Whether there are any 

 authentic specimens in u collection, and what they prove, I know 

 not ; but from what has been said, we will do well to revert to the 

 name G. sulcatum Lam., which seems well established. 



There are a number of typographical and other errors, and mis- 

 takes in the article ; e. g., under Paludina, three species are desig- 

 nated as " L." : Siibcarinuta, Virginica, Vivipara ; evidently the 

 author had ranged them under Lymncea previously, and then forgot 

 to change the genus initials. Under Anodonta marginata, pi. 3, 

 fig. 3, is cited; evidently it should be fig. 5, although the dimensions 

 do not agree exactly with the description, as they do with respect to 

 other species. Helix thyroidus is described. What good reason is 

 there now to spell thyroides, after the original spelling had been gen- 

 erally adopted until 1850, and partly later? I allude to this, as 

 compared with Planorbis exacitous, which is not in the article con- 

 sidered, that Say himself changed, corrected, the nonsensical and 



Probably altitude, in conformity with Say's terminology ; no "breadth " is 

 given. 



