MUSSELS AND: PECTENS 29 
near Tucson, at Laguna Station, San Diego Co., 
Cal., and also in Mexico. 
Anodonta beringiana, Midd., Bering’s Anodon. 
This A. yuokanensis, Lea, of which the descrip- 
tion is as follows: ‘‘Shell smooth, elliptical, very 
much inflated, very inequilateral, somewhat  bi- 
angular behind, rounded before; valves somewhat 
thick, beaks a little prominent, somewhat undulate 
at the tips; epidermis dark brown, without rays; 
nacre whitish. This species lives in Kamchatka 
and vicinity.’’ Dr. Lea’s specimens were sup- 
posed to have come from the Yukon River. 
Gonidea angulata, Lea, the Angled Anodon, 
Figure 138, (Anodonta angulata). The typical 
form is very distinct, a sharp ridge dividing the 
shell into two unequal parts, as shown in the cut. 
This ridge fades out, however, in other specimens, 
and is sometimes nearly or quite wanting. The epi- 
dermis is dark brown, the shell pearly within, and 
