252 Annals of the Carnegie Museum. 



the wider. Anterior attachment of gills as 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, 1911a, pi. 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 sphaerica (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 these 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. I 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. sphcerica, is before me. 



Since there is only a male, the characteristic (2»adrM/a-structure 

 cannot be made out. But I have no doubt that this is a Quadrula on 

 account of its close affinity to Q. sphcerica. In fact all the details, 

 both of the shell and the soft parts, are identical with the latter, 

 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. sphcerica in this character. 

 I should not be astonished, if refulgens should turn out to be a mere 

 " form " of sphcerica. 



