252 ANNALS OF THE CARNEGIE MUSEUM. 
the wider. Anterior attachment of gillsas usual. Diaphragm normal. 
Inner lamina of inner gills free from abdominal sac except at anterior 
end. 
Gills with well-developed septa, which are rather distant in the male. 
In the female, all four gills are marsupial, the septa being close together, 
and the water-tubes narrow. In the inner gill the septa are slightly 
less crowded near the base, but they have the characteristic marsupial 
structure (see Ortmann, 191Ia, pl. 7, fig. 1). 
The glochidia are figured by Lefevre and Curtis (1910, p. 97, fig. F). 
Length 0.23; height 0.32, which is unusually large for this group of 
genera. 
The color of the soft parts is grayish, or yellowish white. 
Quadrula spherica (Lea). 
Three sterile females from Pearl River, Jackson, Hinds Co., Missis- 
sippi, are at hand, collected on Nov. 5, 1910, by A. A. Hinkley. 
Structure essentially as in Q. pustulosa. Anal opening with fine 
crenulations, almost smooth. In all three specimens all four gills 
possess the marsupial structure, and the water-tubes of the inner gills 
are also not quite so narrow as those of the outer gills, chiefly near the 
base. 
By its shell this species is very closely allied to the foregoing, and 
the soft parts are practically identical. JI hardly think they are speci- 
fically distinct, and among the specimens of pustulosa from Ouachita 
River, mentioned above, there are intergrades between the two forms, 
Quadrula refulgens (Lea). 
One male, collected together with Q. spherica, is before me. 
Since there is only a male, the characteristic Quadrula-structure 
cannot be made out. But I have no doubt that this is a Quadrula on 
account of its close affinity to Q. spherica. In fact all the details, 
both of the shell and the soft parts, are identical with the Jatter, 
except that the shell is more compressed (lenticular) in Q. refulgens. 
My specimen is more rounded in outline than the original figure of 
Lea, and thus more nearly approaches Q. spherica in this character. 
I should not be astonished, if refulgens should turn out to be a mere 
“form” of spherica. 
