334 Annals of the Carnegie Museum. 



Proptera purpurata (Lamarck). 



One male, and two sterile females from Bayou Pierre, De Soto 

 Parish, Louisiana, have been sent by L. S. Frierson, and three males 

 from Ouachita River, Arkadelphia, Clark Co., Arkansas, by H. E. 

 Wheeler. 



Description of soft parts given by Lea (Obs., X, 1863, p. 436). 



This species is closely allied to the foregoing, and is its representative 

 form in the south. The close relationship is borne out by the soft 

 parts, which are absolutely identical. I have not seen the glochidia, 

 but they have been described and figured by Lea (Obs., XIII, 1874, 

 p. 73, pi. 21, fig. 13). They much resemble those of P. alata, but since 

 Lea does not give the proportions, a closer comparison is impossible. 



Proptera laevissima (Lea). 



I myself found a young male in the Ohio River, Portsmouth, Scioto 

 Co., Ohio, and received, from R. L. Moodie, four males, and three 

 gravid females from the Kansas River, Lawrence, Douglas Co., 

 Kansas. 



Soft parts described by Lea (Obs., X, 1863, p. 425). 



Simpson places this species near L. gracilis, but the shape of the 

 glochidia (see Plate XX, fig. 2) shows that it belongs to Proptera, 

 and is related to P. alata. The soft parts, although similar in the 

 genera Proptera and Paraptera, are more like Proptera, because of the 

 shorter mantle-connection between the anal and the supra-anal. 

 The glochidia are of the Proptera-type, but they differ distinctly from 

 those of P. alata in being considerably smaller, and in having the 

 ventral margin broader and more curved. The difference in shape is 

 well expressed in Lea's figure (Obs., VI, 1858, pi. 5, fig. 24; see also 

 Coker and Surber, 1911, pi. I, fig. 1) while that of size is not. 

 Length 0.12; height 0.18 mm. (Coker and Surber give length 0.095 

 mm.; height 0.15 mm.). 



Genus Medionidus Simpson. (1900.) 

 (Simpson, 1900&, p. 588.) 

 Shell elongated. Posterior slope plicately or nodulously wrinkled. 

 Beak-sculpture of the double-looped type, indistinct. Epidermis 

 yellowish green, with green rays and blotches. Shell of the female 

 different from that of the male, somewhat swollen just behind the 

 middle of the base. 



