ORTMANN: FAMILIES AND GENERA OF NAJADES. 327 
In every respect like the two preceding species. Mantle-connection 
between anal and supra-anal shorter than anal, the latter with crenu- 
lations, the branchial with papilla. Inner mantle edge of the female 
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. Placente and 
glochidia unknown. 
Fic. 21. Nephronajas sapotalensis (Lea). Sterile female, from Hueyapam 
River, State of Vera Cruz, Mexico. (Carn. 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, 1900), 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, 
