62 THE NAUTILUS. 
Pachychilus glaphyrus Morelet. 
This species is an exceedingly variable one, more so perhaps than 
any other Mexican Melanian. The American student, however, 
will readily call to mind cases of equal variability among the species 
of our Southern States. The material sent by Prof. Rovirosa com- 
prises a number of varietal forms not before made known. 
P. glaphyrus Rovirosai Pils. (PI. I, figs. 9, 10.) 
Shell large and heavy, elevated conical, the lateral outlines 
straight above, modified by the slight convexity of the whorls below. 
Spire more or less truncated at tip, half-grown specimens, (PI. I, fig. 
9,) possessing 8 remaining whorls ; adults, (PI. I, fig. 10,) having one 
or two whorls less. 
Surface most minutely spirally striated the striz visible only 
under a lens. Young and half-grown specimens are otherwise 
smooth, except for very slight spiral lire toward the base. When 
a little more than half-grown, there appear coarse, oblique, curved 
wave-like folds on the body-whorl, extending to the periphery but 
not below it. Simultaneously with these undulations, begin spiral 
spaced lirze crossing them, which are slightly more prominent on 
the crests of the waves. This sculpture continues upon all subse- 
quent volutions. The last volution of an adult specimen is slightly 
compressed below the suture, then quite convex. It has ten waves, 
and about nine spiral lire, but the number of these last is quite 
variable on different specimens. 
The color is olive in young, blackish in old examples: interior of 
the mouth white, maculated with brown at the position of the 
periphery and folds. This marking is also seen on the eroded spire 
in some specimens. 
Aperture ovate, acute above, slightly exceeding one-third the 
total length of the shell. Columella white, regularly arcuate, 
spreading in a brown-tinted callus. 
Dimensions. An adult specimen measures: Alt. 78, diam. 28 
mm. Aperture, alt. 25, width 18 mm. A younger specimen 
measures: Alt.56,diam.20 mm. Aperture, alt. 20, diam. 123 mm. 
Collected from a spring which gushes from the western brow of 
the little ridge of the Limon, State of Tabasco, Mexico. 
This form is allied to P. glaphyrus typical, and to the var. scam- 
nata, but it is distinct from both. The form is notable for its stout, 
straight-sided spire, non-impressed sutures, and the unsculptured 
young. 
