56 THE NAUTILUS. 



The glochidia have been figured by Lefevre and Curtis (Bull. 

 Bur. Fish., 30 [1910], 1912, pi. 8f.'l3, 14, 15), and the fig. 13 

 gives the shape correctly, but measurements have not been 

 published. Lefevre and Curtis (Journ. Exper. Zool., 9, 1910, 

 p. 95), point to the glochidia of this species as having a shape, 

 which might be regarded as transitional tovi^ard the '* axe-head " 

 (or "celt") glochidia oi Proptera. This is quite right; but 

 the glochidia found in the subgenus Micromya of Eurynia are 

 yet closer to the axe-head type. 



The same authors have published (1910, pi. 1, f. 2; 1912, pi. 

 6, f. 2), a general figure of the soft parts of the gravid female. 



In shell characters, this species is near E. nasuta (Say), but 

 the papillae of the mantle edge are somewhat larger, and not as 

 closely set. This makes it, to a degree, transitional between 

 typical Eurynia and the subgenus Micromya. With regard to 

 the glochidia, E. subrostrata is more closely allied to E. nasuta. 

 Also E. recta (Lamarck) has subovate, and not subspatulate 

 glochidia. 

 Lampsilis ventricosa satur (Lea). (See: Simpson, 1900, 



p. 527). 



A number of specimens from the Old River of the Ouachita 

 River, Arkadelphia, Clark Co., Ark., collected by H. E. Wheeler, 

 on May 19 and June 26, 1911, among them gravid females with 

 glochidia, discharging on the latter date. 



Soft parts entirely like those of L. ventricosa (Barnes). 



Glochidia like those of L. ventricosa in shape, subovate, but 

 distinctly smaller. Length, 0.22: height, 0.25 mm. (0.25 X 

 0.29 in ventricosa). 



This form, according to Simpson, is " a rather delicate, dark 

 colored variety of rew^ncosws." There is nothing "delicate" 

 about my specimens. The form satur was founded upon a 

 female, and the male has never been figured. I have males. 

 Both sexes differ from ventricosa by greater convexity of the 

 valves, more prominent umbones, and by dark color. The 

 peculiar emargination of the posterior margin of the female is 

 an individual character, restricted to old specimens. Some of 

 my younger specimens are lighter in color, dark olive-green, 

 and have rays. A very similar form is L. excavata (Lea) 



