84 THE NAUTILUS. 



sterile females of the swollen form (dolabelloides) of the lower 

 Clinch and the French Broad Rivers. 



The structure of the soft parts is identical with that of Lex- 

 ingtonia subplana (Conr. ). (See: Ortmann, NAUTIL. 28, '14, p. 

 28.) It differs from that of the genus Pleurobema chiefly in the 

 cylindrical placentae of deep red color. 



Anal and supraanal openings separated by a short mantle 

 connection, which is sometimes absent (torn?). Branchial 

 opening with papillae, anal with crenulations. Posterior mar- 

 gins of palpi connected at base. Gills broad, the inner some- 

 what broader than the outer. Inner lamina of inner gills free 

 from abdominal sac except at anterior end. Outer gills mar- 

 supial; when charged very little swollen. Placentae well de- 

 veloped, of subcylindrical shape. 



Glochidia, in the specimens preserved, all unripe, but in one 

 of them, collected on July 5, they were sufficiently formed so 

 as to permit examination of shape and measurements. They 

 are subelliptical in outline, higher than long, L. 0.16, H. 

 0.13 mm. 



Color of soft parts orange, in most cases very intensely so, 

 chiefly the foot, adductor muscles, and mantle-margin. Rarely 

 the soft parts are paler, and occasionally they are whitish in 

 young specimens. Among the larger gravid females in one only 

 the shell is marked; " pale, marsupium cream; " but the speci- 

 men clearly belongs here, as is shown by the subcylindrical 

 placentae. Gonads, eggs and placentae generally deep red, but 

 in a few cases, the gonads have been marked as " orange," and 

 in a few other cases the marsupium has been marked as " pink " 

 or " cream color." However, in two male? of the swollen form 

 from French Broad River, the soft parts were pale. This is a 

 remarkable exception, and quite interesting in so far as also 

 other Naiades which the normally tinted tend to assume paler 

 color of the soft parts in French Broad River. 



According to the soft parts this species is a Lexingtonia. I 

 have (1. c. ) mentioned the beak-sculpture of L. subplana as a 

 possible additional character of this genus. In the present 

 species this consists of a number (six to eight) of fine, rather 

 crowded, irregular, and wavy bars, distinct only anteriorly, 



