372 MEXICAN BOUyDARY SHELLS— BALL. vol.xix. 



vertical; anterior adductor scar small and deep, posterior round and 

 well impressed; palleal line well defined; nacre a soft, silv^ery wliite. 



Lengtli of type 55, height .'j3, diameter I'O mm. 



Guadalupe Eiver, Victoria County, Texas, J. D. Mitchell. 



This species, which was first sent to the National Museum by Mr. 

 Mitchell, taken at the above locality, has since been received from 

 Mr. J. A. Singley from the Guadalupe Eivcr at Xew Braunfels, and 

 from the United States Agricultural Exploring Expedition from the 

 Eio Salado, New Leon, Mexico; and in all there are now in the collec- 

 tion fourteen specimens. The species varies greatly in size and consid- 

 erably in form, the Mexican shell being 92 mm. in length by oo mm. 

 in heiglit. Young s])ecimens show faint traces of dark rays in the mid- 

 dle of the shell, and some individuals have slight traces of pustules. 



In other shells there are very slight plications on the disk and on 

 the posterior slope. Two specimens from the Guadalupe liixer in Vic 

 toria County are much shorter and wider, and are lighter colored than 

 the rest, and recall Unio aureus to some extent. The species probal)ly 

 groups with Unto roiveUi and seumnatus, though no other members ol 

 the group have pustules or plications. 



Genus ANODONTA, Bruguiere. 



ANODONTA DEJECTA, Lewis. 



(Plate XXXII, figs. 4,5.) 



Anodonta dejecta, Lkwis, Field and Forest, August and September, Nos. 2 and 3, 



1875, p. 26. 

 Anodonta mearnsiana, Simpson, Nautilus, YI, No. 12, April, 1893, p. 134. 



This species was described by Dr. Lewis, but not figured, in Field 

 and Forest. It was brought with the material of the expedition under 

 Lieut. George M. Wheeler west of the one hundredth meridian, and was 

 said to have been collected by Dr. H. C. Yarrow, naturalist of the expe- 

 dition, in the Arkansas River or its tributaries. The types werei)laced 

 in the ^STational Museum, but by some accident were put away with a 

 lot of rubbish. 



When Dr. Mearns sent the shell from San Bernardino ranch the 

 writer could not identify it with anything and concluded that it was 

 new and named it in honor of its discoverer. Subsequently in going 

 over and arranging the entire naiad collection of the National Museum, 

 I found Lewis' types, and saw at once that his species and my matrns- 

 iana Avere the same. Lewis' types consist of a pair and a left valve, 

 all considerably broken and somewhat distorted, j'et from their jteculiar 

 form, the color of the nacre and epidermis, and the texture of the shell, 

 there can be no doubt of the identity of the two. 



Though differing much in appearance from Anodonta angulata, Lea, 

 the two species are closely related — a fact that would never be sus- 

 pected if it were not that intermediate specimens almost connect the 

 two. Certain specimens of A. amjulata are almost entirely destitute 



