340 PROCEEDINGS OF THE ACADEMY OF [1892. 



entire body-whorl spirally lirate (liri^ on body-whorl 9, on penulti- 

 mate whorl 3) and strongly plicate. 



P. glaphyrus potamarchus. (PI. XIV, fig. 7.) 



This is one of the largest forms of Pachychilus known, and it is 

 the most aberrant of the glaphyrus stock. The shell is rather 

 slender and acutely conical, the outline of the spire being straight. 

 The aperture is ovate, narrowed above, and one-third the length of 

 the shell. Whorls 10-11 remaining, several of the earlier being 

 lost by erosion. The microscopic sculpture is the same as in var. 

 Rovirosai. There are no traces whatever of the waves or folds so 

 prominently shown by the other varieties of glaplnjms, and the 

 spiral cords are also completely obsolete, or indicated by the faintest 

 traces on the base. The color is olive-green or olive-brown. 



Alt. 99, diam. 33 mill. 



Alt. 87, diam. 29 mill. Tabasco, Mexico. 



This variety differs from the pyramidalis of Morelet in being 

 larger and smoother, lacking altogether the chestnut colored spirals 

 of that form. 



P. chrysalis Brot. 



The specimens are large (alt. 60, diam. 27 mill. ; alt. of aperture 

 25 mill.) and have nearly perfect apices. They were collected at 

 Ixtacomitan, Chiapas, where they are called " Shote." There can be 

 little doubt that P. larvatus Brot is a synonym of chrysalis. 



P. corvinus Morelet. 



The specimens were collected at the Montanas de Poanji, Tabasco. 

 They differ from Crosse and Fischer's figures in having the callus 

 at the upper termination of the inner lip much heavier. 



Pachychilus n. sp. 



This is a form resembling closely in contour and sculpture the P. 

 subexarahis C. & F. and also P. largillierti Phil., but differing from 

 both in possessing an extremely heavy deposit of callus at the upper 

 termination of the inner lip. The specimens were collected on the 

 mountains of Poana, state of Tabasco. As none having the cuticle 

 preserved are at hand, I refrain from giving a full description or 

 name. 



Potamanax subgen. nov. 



Shell solid, oval with short conic spire, spirally sculptured or 

 banded. Aperture ovate, acute above, broadly rounded below; 



