NO. nil. PROCEEDINaS OF THE NATIONAL MUSEUM. 373 



of the strong, sharp ridge on the posterior slope, which is usually char- 

 acteristic of that species. They are more compressed and thinner in 

 texture, and are much like ^4.. dejecta in the lurid color of the nacre, 

 general texture, and color of the epidermis, as well as the beak sculp- 

 ture j and the soft parts of the two are much alike. 



Hemphill states ^ that Anodonta angtilata burrows in beds of compact 

 sand and gravel in the Snake River, with the smaller end of the shell 

 downward, and the angular solid end level with the surface, and no 

 doubt this thickening of the shell and the prominent ridge tend to 

 strengthen it against the shocks of the current. The thinner and 

 more compressed specimens of A. angulata probably live in less rapid 

 water, and Dr. Mearns found A. dejecta in soft mud. 



The following is a description of A. dejecta, prepared from a large 

 number of individuals : 



Shell rhomboid or rhomboid-oval, sometimes slightly alate, com- 

 pressed anteriorly, gradually becoming inflated j^osteriorly, smooth 

 and shining, with numerous lightly marked growth lines, moderately 

 solid; having a thin epidermis which easily wears off" in exposed 

 places, varying from bright green to brownish and pale yellow, some- 

 times broadly and faintly rayed in the posterior region; beaks rather 

 compressed, sculptured with a half dozen or more wavy, concentric sul- 

 cations; nacre soft, lurid, brownish or purplish in the cavity of the 

 shell, shading to lighter color at the edges. 



Length of an average specimen 80, height 45, diameter 22 mm. 



San Bernardino ranch, Mexican boundary, Arizona. 



This species was found by Dr. Mearns in the following additional 

 localities: Tucson, Arizona; Colorado Eiver, near the Mexican bound- 

 ary; Santa Cruz River, near Tucson, Arizona; San Bernardino River, 

 Mexican boundary; New River, Laguua Station, San Diego County, 

 California; mouth of Colorado River. 



ANODONTA CALIFORNIENSIS, Lea. 



Anodonta californiensis, Lea, Trans. Am. Phil. Soc, X, pi. xxv, fig. 45; Obser- 

 vations on the Genus Unio, V, p. 42, pi. xxv, fig. XLVii. 



■ Specimens of what are perhaps this species, but which are too much 

 worn to be determined with certainty, were found at monument 219, 

 Mexican boundary line, and at New River, Laguna Station, San Diego 

 County, California. These were merely bleached valves, generally 

 without any epidermis, and in some cases lacking a part or all of 

 the outer shell layer. Wherever the beak sculpture remained it was 

 shown to be much finer and to have more numerous sulcations than 

 that of ^1. dejecta, and in this respect it is like that of A. californiensis. 

 The two species evidently approach closely, and I believe the group 

 typified by Anodonta angulata to be nearly related to that of which 

 A. californiensis is a member. 



1 Zee, I, No. II, p. 326. 



