NEW UNIONID/E OF THE UNITED STATES. 97 



is of a reddish brown ; but when the nacre is white, it inclines to lighter brown. Five 

 specimens are rosaceous, two salmon tinted and two white. None of the specimens 

 had perfect tips on the beaks, and therefore the character of the undulations is un- 

 known. It is likely they will be found to be the same as those of rubiginosw, closely 

 corrugate. 



Unio flavidulus. PI. 15, fig. 245. 



Testa laevi, elliptica, subinflata, valde inoequilaterali, postice obtuse angulata, antice rotunda ; valvulis sub- 

 tenuibus, antice crassioribus; natibus prominulis; epideroiide vel luteo-fusca vel luteo-viridi, eradiata ; 

 dentibus cardinalibus parviusculis, ereetis, conipressis, in utroque valvulo duplicibus; lateralibus sub- 

 longis, lam.ellatis, subreetisque ; ruargarita alba et iridescente. 



Shell smooth, elliptical, rather inflated, very inequilateral, obtusely angular be- 

 hind, round before; valves somewhat thin, thicker before ; beaks slightly prominent ; 

 epidermis yellowish brown or yellowish green, without rays; cardinal teeth somewhat 

 small, erect, compressed and double in both valves ; lateral teeth rather long, lamellar 

 and nearly straight ; nacre white and iridescent. 

 Proe. Acad. Nat. Sci. 1861, p. 39. 



Hah. — Stream near Columbus, Mississippi. Wm. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

 Diam. -6, Length -9, Breadth 1-5 inch. 



Shell smooth, elliptical, rather inflated, very inequilateral, obtusely angular behind, 

 round before ; substance of the shell somewhat thin, thicker before ; beaks a little 

 prominent; ligament small, thin and dark brown; epidermis yellowish brown or 

 greenish on the sides, without rays, with rather close, equidistant lines of growth ; 

 umbonial slope somewhat raised and round, or very obtusely rounded ; posterior 

 slope rather narrow, elliptical, yellow with two greenish lines on each valve from the 

 beaks to the posterior margin ; cardinal teeth rather small, erect, compressed, double 

 in both valves ; lateral teeth somewhat long, lamellar and straight ; anterior cica- 

 trices distinct, small and well impressed ; posterior cicatrices distinct, rather large 

 and slightly impressed ; dorsal cicatrices under the plate, and across the base of the 

 cardinal tooth; cavity of the shell moderately deep and wide; cavity of the beaks 

 rather shallow and subangular ; nacre white and iridescent. 



Remarhs. — This is a small species of a nearly regular ellipse. The largest of four 

 is 1 J inches wide and nine-tenths long. In outline it is very near to the male of 

 parvus, Bar., but it belongs to the natural group of which Hanleyanus (nobis) may 

 be considered the type ; it is not, however, an oblique species having a nearly 

 regular transverse elliptical form. It is totally different from ^xutus in the color of 

 the epidermis, and the nacre is not pearly but rather a dead white. In color and 

 general aspect it reminds one at once of Hanleyanus, but it is not so thick and is not 



25 



