39 



shells. Color of the nacre white to deep pink. 

 This and the preceeding species are closely 

 related and yet constantly distinct. 



123. Unio rubiginosus Lea. Common in the river and 



canal. Nacre milky white to salmon colored. 



124. Unio subrotundus Lea. River, abundant, and 



very variable. In some specimens, the beaks 

 are verj- prominent, even so that extreme 

 forms resemble U. pyramidatus, while others 

 are hardly distinguishable from large U. 

 coccineus, in shape; the soft parts, however, 

 and also the nacre are characteristic enough 

 to separate them. The following are forms 

 more remote from the type. 



rar kirtlandianus Lea. Little inflated, with the out- 

 lines snbquadrate. 



var. — Umbones very large and quite anterior; striae 

 of growth coarse and regular; little con- 

 nected with the type and found only in 

 certain localities. 



125. Unio aesopus Green. Frequent in the river a 



few miles above Canal Dover : scarce else- 

 where. 



126. Unio clavus hcim. River, not common. 



127. Unio gibbosus Barnes. Common in the river; 



rare in the Ohio canal. Many old specimens 

 are strongly curved downward in the 

 posterior part. The female shells are more 

 inflated, in the average, than the male. 

 F. arctior Lea. Not common; nacre white 

 or salmon colored. Also specimens inter- 

 mediate in color between the type and this 

 form, which can not even be regarded as a 

 variety. 



128. Unio complanatus Sol. A single, large and well 



formed specimen was found in a mill race on 

 the river, at New Philadelphia ; the first 

 instance of its having been collected in the 

 Ohio drainage. This eastern species has evi- 



