254 AMERICAN JOURNAL 



Dipsas of Leach, and if Dr. Gray had had a perfect specimen 

 before him when describing Anodonta tenuis, he never would 

 have placed it in that genus. The Dipsasian character was 

 evidently obliterated by age in the specimen from which he made 

 his diagnosis. The young specimens, and the mature perfect 

 ones, always have the tooth (so to call it) of the genus Dipsas. 

 I described this species in the Transactions of the American 

 Philosophical Society, March 15, 1833, under the name of 

 Symphynota discoidea, with a figure perfectly representing the 

 characteristic tooth, which consists of a single raised, slightly 

 curved line under the dorsal margin. In my ' Synopsis,' in the 

 first edition in 1836, as well as in the second and third editions, 

 I gave Dr. Gray's tenuis as a synonym to this shell, which I 

 therefore placed in the genus Dipsas, where it properly belongs. 

 It must therefore stand as Dipsas discoidea, Lea, with the 

 svnonym of Anodonta tenuis, Gray ; my date being 1833, and 

 Dr. Gray's 1834. 



"In this paper of Messrs. Baird and Adams, they have de- 

 scribed a supposed new species from Shanghai, under the name 

 Unio (Lampsilis) subtortus.- I previously published a descrip- 

 tion of a species which I believe will prove the same, under the 

 name of tortuosus, in the Proc. Acad. Nat. Sci. April 18, 1865. 

 Since then I have found in the 'Journal de Conchiliologie,' July, 

 1863, — which work for that year was not accessible to mo, — 

 that Messrs. Crosse and Debeaux had given a description and an 

 excellent figure of a Unio of the same twisted character, under 

 the name of Tientsinensis, which, if the figure be entirely cor- 

 rect, differs in the form of the posterior slope, and in the undu- 

 lations of that part. 



I may be permitted to express my surprise that neithe'r the 

 French nor the English authors should have observed the very 

 remarkable character of these Chinese species, which were before 

 them, in being inequivalve ! The figure in the Journal de Qon- 

 chyliologie seems to be very correctly delineated by the artist, 

 having represented the inequivalve condition of the right and 

 left valves. 



" Messrs. Baird and Adams refer to Tientsinensis, but con- 

 sider it to differ in some respects from their subtortus, which I 

 think very likely. If Tientsinensis prove to be the same as tor- 

 tuosus and subtortus, then the two last must be synonyms. If 

 not, then there will be two species, viz. : Tientsinensis, Crosse 

 and Debeaux, and tortuosus (nobis), — subtortus, B. and A., being 

 a synonym to tortuosus." 



