— 10 — 



able; some older, large specimens have lost the 

 epiconch all over. In some the nacre is rose col- 

 ored; one shell has three well formed cardinal 

 teeth in either valve. — A very peculiar observa- 

 tion has been made on a large female specimen. It 

 was in sand, under about ten inches of clear, quiet 

 water; the posterior, protruding part of its mantle, 

 was widely expanded and regularly undulating, 

 waving, probably to produce an increased current 

 of water for the benefit of the embryones in the 

 branchial uteri. This is the first and only time I 

 noticed this movement, which, however, must be 

 further observed, as it could not be such an excep- 

 tional phenomenon. 



105. Unio multiradiatus Lea. River, not rare. 



106. Unto rangianus Lea. River, rather scarce. 



107. Unio iriss Lea. River, rather scarce. 



108. Unio novi eboraci Lea. River, noc rare. This 



and the preceding, while rather different in the ex- 

 treme forms, are nearly related and some specimens 

 seem to be intermediate. 



109. Unio fabalis Lea. River, not scarce; the female 



average smaller than the male. In July, 1893, an 

 adult male was found with a byssus thread. 



110. Unio parvus Barnes. Scarce in the river; common 



in the Ohio canal. At the margin of the posterior 

 part of the mantle, there is a comparatively large 

 pallial eye on either side. 



111. Unio lens Lea. Common in the river, sometimes 



with the nacre purple. The branchial uteri are of 

 the same type as. in U. ligamentinus, subovatus, 

 multiradiatus, etc.; this and the corresponding dif- 

 ference in shape of the shells with the sexes, as well 

 as characters of the hinge, range U. lens under a 

 group with those species, while in the outer appear- 

 ance of the shell it shows similarities with the coe- 

 cineus, etc., group, 



112. Unio circulus Lea. Common in the river. This is 



one of our most peculiar shells. (Identified by Mr. 

 Chas. T. Simpson.) 



