208 



Unio riigosus, Barnes. SilUman's Jowrn., vol. 6, p. 126. Hil- 

 dreth, SilUman's Journ., vol. 14, j?. 282. 



Unio lacrymosus, "| Trans. Amer. Phios. Soc, i\^. *S^., vol. 3 

 Tfnio aspern'mus, j and 4:. 



Desc. Shell narrowed, compressed and thin before ; short, ob- 

 tuse, rounded and wider behind : beaks slightly elevated ; liga- 

 ment more elevated than the beaks ; hinge margin compressed, 

 carinate ; basal margin falcate, emarginate, and compressed ; an- 

 terior margin subangulate ; anterior dorsal margin sub truncate, 

 nearly straight; anterior basal margin projecting; epidermis dark 

 brown, under the epidermis pearly white ; sui-face rough and scaly, 

 wrinkled transversely and waved longitudinally, having distinct 

 irregular transversely compressed tubercles ; a broad nodulus, ele- 

 vated, somewhat double ridge extending from the beaks to the 

 anterior basal edge, and projecting on that part; a broad furrow or 

 wave behind the ridge ending in the emarginate basal edge, and a 

 furrow before separating the anterior hinge and anterior dorsal 

 margin ; cardinal teeth sulcated ; lateral tooth striated, rough, and 

 in the left valve somewhat double ; posterior muscular impression 

 deep and partly rough ; cavity of the beaks angular, compressed 

 and directed backward under the cardinal tooth; naker pearly 

 white, and on the fore part iridescent. 



Oh.'i. The above is Barnes' description of this strongly marked, 

 common species. It is an inhabitant of the Ohio and its tributa- 

 ries, and approximates, by its varieties to some of the varieties of 

 T'. lullatus, Raf. Barnes compares it with the U. verrucosus, 

 Raf., to which, however, it has but a remote affinity. I have re- 

 ceived specimens from Dr. Hildreth of Marietta and Mr. Barabino 

 of New Orleans. The impressions of the plate, with Barnes' name 

 of rugosus, were colored before I received the " Monograph of the 

 Bivalve shells of the Ohio," the faithftil translation of which, Mr. 

 Poulson presented to me. PL 53. 



Planorbis. — Shell univalve, thin, fragile, discoidal or revolving 

 in the same horizontal plane ; concave above and beneath, the spire, 

 being impressed ; aperture rounded-ovate, entire at base, the labia 

 interrupted by the convexity of the penultimate volution ; labrum 

 simple ; operculum none. Animal depressed, spiral sinistral ; foot 

 rounded, small ; tentaeula two, long, slender, contractile ; eyes at 

 the inner base of the tentaeula ; mouth somewhat exertile, armed 



