28 THE NAUTILUS. 



typical form described," represented in PI. I, fig 6 (1. c. No. 7). 

 Probably I had a greater number of examples at disposition than 

 Mr. Pilsbry ; the two forms proved to be distinct by an entirely 

 different formation of the lamelL^e as well as of the basal part of 

 the shell. And among the whole number I found not one interme- 

 diate or doubtful specimen. There is no doubt but that we have to 

 consider them as being specifically distinct, the more so since they 

 live together in the same locality. For the new species I would 

 propose the name : P. Hemphilli, in honor of the man to whom we 

 owe so many valuable additions to our malacological fauna. 



As in shape and general appearance the two species are almost 

 alike, it may be the best way to characterize the one in question by 

 comparing it with P. calamitosa, Pilsb. P. Hemjjhilli averages a 

 trifle larger than its companion, but either is somewhat variable in 

 size. While calamitosa has a minute perforation, hemphiUi is 

 iimbilicated in quite a peculiar way : there is a nodule-like projec- 

 tion on the umbilical part of the last whorl producing a rima 

 beside the umbilicus ; in calamitosa there is nothing of this forma- 

 tion. On the other hand, the latter has a small but distinct groove- 

 like impression just at the base, near the aperture appearing as a 

 slight projection inside ; this feature is wanting in hemphilli. — 

 Lamellae : in the latter species, when looking from front only one 

 is generally seen in the palatal wall, corresponding to the superior 

 one in calamitosa, but longer, i. e., beginning deeper in the throat, 

 and fairly seen on the outside, also marked there by a corresponding 

 impression, ascending in a curve from near the base ; a little distant 

 from its inner end, just above the projection mentioned, there is 

 another lamella beginning, directed toward the base and ending 

 there, also seen on the outside. Quite generally there is a very 

 small, thin, but well formed lamella in the palatal wall near the 

 j^rojecting auricle. The columellar fold is quite short and small in 

 hemphilli yet consisting of a vertical and a horizontal part ; the 

 (main) apertural lamella is decidedly longer in our species, and the 

 supra-apertural higher and entire while in calamitosa it is evidently 

 composed of two parts marked by an indentation in the middle, or 

 even entirely separated, in quite mature specimens. 



About 20 examples, collected at San Diego, Cal., by Mr. Hemphill, 

 are all P. hemphilli, no cahonitosa among them. They are little 

 diflferent from the St. Thomas River specimens, except by a some- 

 what shorter palatal lamella. 



