136 THE NAUTILUS. 



CONTRIBUTION TO A KNOWLEDGE OF UNITED STATES UNIONID.E. 



BY S. HART WRIGHT. 



Unio Pinkstonii sp. nov. 



Shell flask-shaped or triangular, clavate, inflated below the beaks, 

 rounded anteriorly and very bluntly pointed behind. Epidermis 

 olive with transmitted light, with numerous close lines of growth ; 

 rayless. Beaks elevated, blunt and nearly on a line with the an- 

 terior margin in old specimens, but the shell very inequilateral in 

 the young. Sides very convex and descending in front very 

 abruptly. Basal margin very convex. Umbonal ridge very blunt, 

 and only slightly raised. Posterior slope narrower, its margin not 

 keeled. Cavity of shell deep, cavity under the beaks slight, bluntly 

 rounded. Cardinal teeth erect, striate ; the anterior cardinal trun- 

 cate. Cardinal in right valve single. Cavity between cardinals 

 with a deep conical pit. Lateral teeth straight and short. Dorsal 

 cicatrices over the beak-cavity. Nacre white, without iridescence, 

 except at the posterior end, where the nacre is thin, it being thick 

 elsewhere. Cicatrices all distinct and well-impressed. Width 1| 

 inches, length 1|, diameter 1. 



Habitat: Tuscaloosa River, Macon Co., Ala. 



Remarks: Affinity, U. castaneus Lea, from which it differs in 

 having a tray-shaped cavity, instead of bowl-shaped, as in the former. 

 Its rings of growth are low and fine, not ridgy and coarse as in old 

 U. castaneus. The U. mix group probably includes this and U. cas- 

 tnii<'iin, U. concolui; U. brumbyanus and U. perovatus, species more 

 or less related to our shell, in which the nacre is laid unevenly in 

 plates and ridges, which form two or more pits where they meet. 

 The species is dedicated to Miss M. S. Pinkston, who assiduously 

 collects Unionidiu, and found this among her collections. 



Unio Kirklandianus f\>. m>v. 



Shell ovate, brilliantly polished, rather thin and somewhat in- 

 flated. Sides dilated in the middle and attenuated at each end. 

 Base very convex ; anterior end rounded and the other bluntly 

 pointed. Epidermis yellowish horn-color, with broad green rays on 

 all the sin-face, which are interrupted near the base with narrow 

 yellow bands. Lines of growth only two or three and ferruginous, 

 lieaks blunt and broad, slightly raised; umbonal ridge raised and 

 abruptly rounded. Posterior area abrupt, narrow and slightly 



