Ortmann; Families and Genera of Najades. 271 



Elliptio gibbosus (Barnes). 



Numerous specimens from the Ohio and Lake Erie drainage in 

 western Pennsj Ivania have been seen, and two males and two females 

 from Arkansas. Gravid females were found in the months of May, 

 J une, and July, and in one case as late as August 13. This is a typical 

 tachytictic form. 



The soft parts have been discussed by Lea (Obs., X, 1863, p. 417) 

 and Simpson (in Baker, 189S, p. 70). 



The beak-sculpture in this species is also similar to that of E. com- 

 planatus, but it is slightly heavier, though less distinct; that is to say: 

 the ridges are thicker, but less well defined. 



Soft parts essentially identical with the other species described in 

 this genus. It, however, should be mentioned that in a very few cases 

 the mantle-connection between the anal and the supra-anal was found 

 missing. The anal has distinct papilla?. 



When gravid the marsupium swells moderately, but the edge re- 

 mains sharp. The ovisacs are leaf-shaped, and the placentae are 

 moderately well-developed, but when the glochidia are formed, they 

 seem to be less distinct. Color of eggs and glochidia always white. 

 Glochidia (see Lea, Obs., XIII, 1874, pi. 21, fig. 10; and Ortmann, 

 191 1£», pi. 89, fig. 7) rather small, suboval in shape, without hooks. 

 Length 0.20, height 0.22 mm. 



Color of soft parts grayish white. Foot, gills, and mantle gray, edge 

 of the latter black posteriorly. Marsupium cream-white. 



Elliptio popei (Lea). 



Two gravid females, from Valles River, Mexico, collected by A. A. 

 Hinkley in December and January, 1906-1907, 18 were received from 

 L. S. Frierson. 



The beak-sculpture is somewhat different from that which is typical 

 of this genus. In the two specimens before me, it is poorly developed, 

 although the beaks are well preserved. It consists of two to three 

 fine concentric ridges, which are somewhat interrupted in the middle, 

 giving a faint appearance of double loops. But it is not by any means 

 double-looped, since no reentering angles are present. 



The soft parts are typical. The anal and supra-anal are separated 

 by a mantle-connection, which is shorter than the anal. Anal with 

 well-developed papilla?; papillae of branchial larger than those of anal. 



18 See Hinkley, 1907, pp. 68 and 79. 



