362 Mr. Barnes's Reclamation of Unios. 



not the generic characters of that genus. It always wants 

 the loxg, compressed lateral tooth, which Lamarck in- 

 serts as a part of his generic description, (alter (sc. dens) 

 elongatus, compressus, lateralis, infra pubem productus,) 

 Lam. Genus Unio, vol. vi, p. 69 ; and yet, Lamarck himself, 

 has put a shell of exactly this kind, at the head of his genus 

 Linio. This fact led me into a mistake concerning the Alas- 

 modonta arcuata, which is Lamarck's Unio sinuatus, and the 

 Mya margaritifera, of authors; and Lamarck has again de- 

 scribed the young of this same species, under the name of 

 Unio elongatus. Neither of these ever has the long, com- 

 pressed, lateral tooth. They, therefore, belong properly to 

 Mr. Say's genus, alasmodonta. Am. conch, p. 14 — 15. 

 Both the young and the old, answering to the two species of 

 Lamarck, just mentioned, are figured in the Journal, vol. vi. 

 pi. 12. The same shell is figured by Pennant and Lister. 

 It is very remarkable, that a shell found in our waters, should 

 be so exactly like one found in Europe. This species, though 

 so well known abroad, was unknown to Mr. Say, when he 

 published his treatise. It was brought to me from Tappan 

 and Canada creek, in this state, and being unknown to Mr. 

 Say, I supposed it new, and so described it. 



I find it difficult to believe, what seems to be a very plain 

 fact ; I suspect there must be some mistake : the figures and 

 description of this shell seem to show an exact identity, and 

 we have compared ours with specimens labeled, Mya marga- 

 ritifera, from Liverpool, Eng. They are the same ; and yet, 

 if the Unio sinuata, of Lamarck, has the long, lateral, lamelli- 

 form tooth, ours is a different shell, and the original name 

 must stand. If that is the fact, neither of us has made a mis- 

 take. In the case of the Unio Mans, of M. Valenciennes, we 

 seem to perceive the same error as that above imputed to La- 

 marck. His shell is from our waters, and we have numerous 

 fine specimens, all of which are destitute of the lateral tooth, 

 by which the genus Unio is characterized. 



This natural and useful genus contains now six species, as 

 follows : — 



1. Alasmodonta margaritifera, Mya L. Unio, Lam. 



2. " complanata, ) American Journal, vol. vi, 



3. " rugosa, 5 P* ?5 — 80. 



4. marginata, ? Say , Am . conch . 1. c. 



5. " undulata, ) 



6. " purpurea, of M. Valenciennes, mentioned 



below. 



