Ortmann: Families and Genera of Najam . 327 



In ever j respect like t he two preceding species. Mantle-connection 

 between anal and supra-anal shorter than anal, the latter with crenu- 

 lations. the branchial with papillae. Inner mantle edge of the fem lie 

 in front of branchial very slightly lamellate, with fine crenulations, and 

 a black streak accompanying it. Palpi with posterior margins con- 

 nected at base. Inner lamina of inner gills entirely connected 

 with abdominal sac. Marsupium formed by numerous (twenty 

 and more) water-tubes, occupying a section of the posterior half of- 

 the outer gill. In the sterile females at hand, the margin of the mar- 

 supium is rounded, projecting slightly beyond the edge of the gill, 

 beaded, and marked with brownish black pigment. Placentae and 

 glochidia unknown. 



mp 



Fig. 21. Xephronajas sapolalensis (Lea). Sterile female, from Hueyapam 

 River, State of Vera Cruz, Mexico. (Cam. Mus., No. 61, 5,000.) 



Color whitish, with the margin of the mantle brown and blackish 

 in the region of the anal and branchial, a blackish streak in front of 

 the branchial, and black pigment on the edge of the marsupium. 



Genus Amygdalonajas Crosse and Fischer. (1893.) 

 Simpson, 19006, p. 604 (as subgenus). 



Shell ovate-triangular, inflated, truncated at posterior slope, with 

 a distinct and often sharp posterior ridge. Disk not sculptured. 

 Beak-sculpture consisting of a few fine ridges, of which the later ones 

 are more or less distinctly sinuated or double-looped. Epidermis yel- 

 lowish green, with a pattern of broken or arrow-marked rays. Male 

 and female shells differing but little, the female shell somewhat inflated 

 at the post-basal region. 



Inner lamina of inner gills entirely connected, or free for a short 

 distance. Inner edge of mantle in front of branchial in the female, 



