46 THE NAUTILUS. 



b c Posterior ridge of shell distinct, rounded or rather 

 sharp. Posterior slope more or less truncated, with 

 distinct corrugations. Cardinal teeth weak, com- 

 pressed, not stumpy, sometimes even obsolete. Epi- 

 dermis with rays which generally break up into a pat- 

 tern of spots. Beak sculpture very heavy, bars slightly 

 sinuate. Female shell not distinguishable from that 

 of the male. Subgenus: Rugifera Simpson. 



(Type: A. marginata Say). 



The position of A. collina (Conrad) is yet doubtful. The 

 type-species of Pressodonta is unknown in its anatomy, but 

 it is very closely allied to A. minor, in fact, the two may be 

 only forms of the same species, so that we may safely assume 

 that they agree in structure. 



ALASMIDONTA (PRESSODONTA) MINOR (Lea) (See: Ortmann, 

 1912, p. 295). 



I collected a number of specimens in the North Fork Hol- 

 ston Eiver, Saltville, Smyth Co., Va. (September 17, 1912), 

 and in Clinch River, at Richland and Cedar Bluff, Tazewell 

 Co., Va. (September 20, 1912). 



The soft parts of this species were described previously 

 from a single male and a single gravid female. In these, the 

 inner lamina of the inner gills was free from the abdominal 

 sac, except at the anterior end. 



From Saltville, I have preserved the soft parts of three 

 males and two gravid females, and they all have the inner 

 lamina of the inner gills entirely connected with the abdomi- 

 nal sac. From Richland I preserved two males and three 

 gravid females : of these, the males have the posterior part of 

 the inner lamina free for about half the length of the abdomi- 

 nal sac, one of the females shows the same condition, but the 

 second has even a larger part of the inner lamina free ( about 

 two-thirds), and the third has it almost entirely connected, 

 only a small hole remains open at the posterior end of the 

 foot. From Cedar Bluff I have the soft parts of a gravid 

 female, and here the inner lamina is free for a little more 

 than one-half of the abdominal sac. 



