342 KANSAS UNIVERSITY SCIENCE BULLETIN. 



which are directed upwards at the dorsal margin. Epidermis 

 dark brown to black in color, rough except over the umbones. 

 Lines of growth coarse and continuous, imbricated margin- 

 ally. Ligament long and stout, black. Lunule large. 



Interior: Pseudocardinals large, high, heavy, ragged, 

 double in the left, and single and sometimes double in the 

 right valve ; when double the right anterior tooth is small 

 and low. Laterals of moderate length, stout, curved slightly 

 downward. Interdentum broad, flat, cut away in the right 

 valve to receive the posterior left pseudocardinal. Anterior 

 muscle cicatrices large, long, and narrow, of only moderate 

 depth, with roughened floors ; adductor cicatrix often curved 

 a little around the anterior pseudocardinal. Posterior scars 

 large, lightly impressed, fused. Pallial line heavily impressed 

 and crenulate anteriorly. Cavity of the beaks not large, of the 

 shell fairly large. Nacre white, very iridescent posteriorly. 



<). plicata ranges from Lake Winnipeg and Lake Erie south 

 to the Arkansas and Tennessee rivers. It is common in all 

 Kansas drainage areas, although it is not as abundant as the 

 closely related Q. undulata. It is reported as far west as the 

 Whitewater river in the Arkansas drainage (Call ) , and as 

 Wild Cat creek, Riley county, in the Kansas drainage (Pope- 

 noe). I do not think that the species ranges much further 

 west than this latter point. Plicata is found buried in deep 

 mud in from two to ten feet of water, along with such forms 

 as Symphynota complanata and Tritogonia turberculata. In 

 favorable conditions the shell becomes very massive and at- 

 tains some size ; a specimen from the Blue river was 165 mm. 

 in length and the dry shell weighed 800 grams. Another 

 specimen was 195 mm. in length. 



Q. plicata is separated from the other undulate Unios by its 

 full, high beaks and curved dorsal margin. The plications 

 are very variable in extent and distinctness. 



