﻿200 rKlKRSONIA 



and purplish helow the palHal line or sometimes silvery white 

 threughout). Pseudocardinal teeth compressed, rather small; 

 lateral teeth very short, about one-third the shell's length. 

 Ligament short. 



Length 47, height 26, diam. 15 mm." (Pilsbry.) 



Type locality, Ganina River, three miles southwest of San 

 Dieguito, Mexico. Also in the Valles River at and above 

 Mecos, Mexico. 

 Lotiiplisis semiraso Pii.sbry, Pr. Ac. N. Sci. Phila., 1909, p. 



534, pi. XXVI, figs. 7. 8. i). 



"Some specimens of the tyi)e lot are larger, length 55, height 

 28, diam. 16 mm. There is also some variation in the teeth^ 

 which may be more or less stout. 



L. semirasa differs from L. signata and L. imdivaga by lack- 

 ing corrugation on the convexity of the valves and on the pos- 

 terior-dorsal slope." 



The following are unfigured and unknown : 

 I.ampsilis fasciola Rafinesque, Ann. Gen. Sci. Brux., V, 1820,. 



p. 299. 

 Lampsilis fnlgens Rafinesque, Cont. Monog., 183 1, p. 7. 

 Lanipsilis argyratus Rafinesoue, Cont. Monog.. 1831, p. 7. 



Genus FRIERSONIA Ortmann, 1912. 



"Shell subelliptical, without distinct posterior ridge. Disk not 

 sculptured. P)eak-sculpture of the double-looped pattern, con- 

 sisting of six to eight fine bars, of which the later ones are 

 distinctly double-looped, and the latest are interru])ted (uncon- 

 nected) in the middle. Epidermis greenish-yellow, with rather 

 distinct, simple rays. Male and female shells hardly different. 



Inner lamina of inner gills connected with abdominal sac. 

 Edge of mantle in front of branchial slightly laminate, with 

 fine and distinct crenulations, disappearing gradually in front, 

 but without papilhe. A brown streak of pigment along this 

 part of the edge. Marsupium consisting of many ovisacs, 

 occupying the larger posterior section of the outer gill. When 



