202 TURNER. 



Other (Fig. 4, B), but neither spines nor other structures 

 project outwards (laterad) from it to the wall of the capsule. 



The testis lies within the wall of the shell and consists of 

 four concentric, unequal-armed, ^'^shaped tubes, which lie 

 above (dorsad of) the lateral diverticulum of the digestive tract. 

 The shorter arm of the U, which is situated above (dorsad of) 

 the long arm, is from one-third to one-half as long as the other 

 arm. Each tube is broadest at the free end of the longer arm, 

 from which extremity it gradually tapers to the free end of the 

 shorter arm, where it terminates in a point. Judging from a 

 half dozen specimens examined, the sperm mother-cells are con- 

 fined to the smaller arm, and the crook which unites that arm 

 to the longer limb of the U. Usually there is a pair of testes, 

 one in each valve of the shell ; but in one of the specimens 

 examined there was a well developed testis in one valve, but 

 not even a trace of a testis in the other. 



Clark University, South Atlanta, Ga., 

 December 24, 1898. 



