ORTMANN: FAMILIES AND GENERA OF NAJADES. 239 
known in European forms, where they incline toward the type of the 
subfamily Anodontine. I have no doubt that this finally will be a 
very important systematic criterion, but unfortunately we do not 
know the glochidia of a single Asiatic species. 
The following provisional division into genera in accordance with 
what has been hereinbefore said is here submitted: 
a. Beak-sculpture ranging from the concentric to the zig-zag type. Mantle con- 
nection between anal and supra-anal absent, deciduous, short, or of 
medium length. Inner lamina of inner gills free from abdominal sac. 
bi. Mantle connection absent or short. Beak-sculpture concentric to zig-zag. 
Glochidia subovate, without hooks. 
ca. All four gills serving as marsupia. Mantle connection between anal 
and supra-anal present, short and deciduous.’ 
d,. Ovisacs and placente subcylindrical, the latter rather persistent, 
generally red. Shell simple, without sculpture upon disk. Beak- 
Sculpture: sitnple, cOncemtricia. cs. ers. ei eieleta ee ns Fusconaja. 
d». Ovisacs and placentz leaf-shaped (compressed and lanceolate), the 
latter rather poorly developed, generally white. Shell with 
sculpture of various patterns. Beak-sculpture concentric, 
double-looped, or zig-zag. 
e1. Shell with oblique undulations upon the disk. Beak-sculpture 
concentric, nearly obliterated, or of zig-zag pattern and 
extending more or less upon the disk............ Crenodonta. 
eo. Shell-sculpture tuberculous or nodulose. Beak-sculpture con- 
centric and disappearing upon the disk, or of the double- 
looped or zig-zag pattern, more or less extending upon the disk. 
Quadrula. 
c.. Marsupium formed by the outer gills only. 
d;. Mantle-connection above anal opening absent, no supra-anal formed. 
Shell tuberculous, beak-sculpture of zig-zag pattern, much 
broken up, extending somewhat upon the disk. Nacre deep 
PUBP LS rey Morse cutee lest eheceeere seme CUS Inrtahe esa ke Rotundaria. 
dy. Mantle connection between anal and supra-anal present, short, or 
deciduous. Beak-sculpture concentric, obliterated toward 
the disc. 
é1. Shell tuberculous. Soft parts of a peculiar orange color. Pla- 
cente pink (at least in one species)........... Plethobasus. 
§ Under this division apparently belong two species occurring in Georgia and 
Florida, infucata Conrad and kleiniana Lea, the soft parts of which have been partly 
described by Lea (Obs., X, 1863, pp. 404 and 407). Inthese species we observe the 
most beautifully developed zig-zag sculpture among North American forms. The 
soft parts are imperfectly known, but the marsupium is formed by all four gills. 
Probably they should form a genus by themselves. 
10 Called ‘‘egg plates”’ by Lillie (1895), and ‘‘conglutinates’’ by Lefevre and Curtis 
{1Q10). 
