FAMILY UNIONIDjE — UNIO. 191 



Lamarck received his specimens from the Susquehannah and Mohawk rivers ; Mr. Barnes, 

 from Wisconsin river and Lake Erie. My specimens were procured from Sandy creek in 

 Orleans county, Wolcott creek and Port bay on Lake Ontario, and from the Little falls and 

 Lake Champlain. It approaches U. tappanianus, but is not as much alated, is a more solid 

 shell, and is evidently distinguished from that shell by the teeth. 



Unio compressus. 



PLATE XXI. FIG. 245. 



(STATE COLLECTION.) 



Symphonota comprasa. Lea, Trans. Phil. Vol. 3, p. 450, pi. 12, fig. 22. 



Margarita (Unio) compressa. Id. lb. Vol. 6, p. 121. 



Unio compressus. Conrad, Fr. Wat. Shells, p. 68. Adams, Am. Jour. Vol.40, p. 276. 



Description. Shell flattened, moderately thin, compressed, subtriangular ; beaks with 

 double concentric undulations : ligament concealed within the valves. Hinge-margin nearly 

 straight, subangular, on the posterior margin. The posterior cardinal toolh in one valve 

 highest, curved, and passing into the lamellar tooth, which is narrowly channelled throughout ; 

 the central one often dentate : a single broad cardinal tooth in the other valve ; the lateral 

 tooth simple, with two rudimentary teeth parallel with it near its termination. 



Color. Olive brown or greenish, which increases in intensity towards the beaks, with occa- 

 sionally faint radiations with bluish white ; salmon-colored towards the cavities of the beaks. 



Vertical axis, 1 • 1 - 1 ' 7 ; transverse ditto, 1 ' 7 - 2 ' 8. 



Through the kindness of the late Dr. Boyd, I have received specimens of this species 

 from Sandy creek in Jefferson county, and Oak-orchard creek in Orleans county. It occurs 

 near Middlebury, Vermont. 



Unio nasutUS. 



plate xx. fig. sm. 



(STATE COLLECTION.) 



Unio namlus. Sat, Nich. Ency. Vol. 4, pi. 4, fig. 1. 



U. Tottralia. Val. Humboldt & Bonpland, Rec. de Zoologie, Vol. 2, p. 233, pi. 53, fig. 



U. nasutus. Barnes, American Jour. Science, Vol. 6, p. 273. 



U. id. Conrad, Monog. pi. 18, fig. 1. Rossel, Essex Jour. Vol. 1, p. 60. 



U. id. Lea, Synopsis, etc., p. 132. Gould, Invertebrata of Mass. p. 109, fig. 71. 



Description. Shell oblong-lanceolate and somewhat produced or rostrated at one extremity, 

 regularly rounded at the other. Valves thin in running streams, more stout and solid in the 

 lakes. Beaks small and little elevated, with a few corrugations. An elevated ridge runs 

 from the beaks to the rostrated extremity, and above this the valves are much depressed, with 

 a few broad radiating furrows on the surface. Lower margin regularly rounded, until it ap- 



