Casey — Notes on the Pleurotomidae. 155 
covered with fine acute longitudinal riblets. The periphery 
is more or less obtusely swollen, the ribs small and numerous 
and reduced in size and reversed in curvature on the broad 
fasciolar surface, generally attaining the suture or small sub- 
sutural collar above. The canal is rather tapering in form, 
straight, moderate in length, and, together with the aperture, 
about half as long as the shell. Of the two following species 
the first is to be regarded as the type: — 
Shell very small, with two or three body whorls, moderately stout, the em- 
bryo of five whorls which gradually and evenly increase in size, the 
apical whorl or nucleus very minute, acutely rounded and relatively 
higher in form, the second to fifth broadly convex and closely covered 
with an elaborate system of fine riblets, becoming more widely spaced 
on the fifth and gradually merging without break into the ribs of the 
subsequent whorls; these ribs are some twelve in number, elevated, 
rounded, extending throughout the convexity of the body whorl below 
and to the very fine subsutural collar above, becoming reduced and 
arcuately reversed in curvature across the fasciolar surface; spiral 
lines moderately coarse, even and flat, rather widely spaced and without 
intermediate lines, becoming close-set near the base and slightly 
smaller and more close-set on the fasciolar surface. Length of a speci- 
men of 2 body whorls, 4.8mm.; width ,1.5 mm. Lower Claiborne 
Eocene of St. Maurice, La.............. aecisidiesine aasas o ECIOOIM NSD. 
Shell slightly larger and rather more slender, with more elevated and less 
obtusely rounded periphery, the aperture and canal combined notice- 
ably shorter than the remainder; embryo relatively larger, higher than 
wide, of about five whorls, the four uppermost smooth, forming alarge 
even cone, the two lower whorls of which are relatively more inflated 
toward base, the fourth acquiring coarse feeble riblets which grow 
stronger on the fifth, where they are broadly arcuate and widely spaced; 
the fifth whorl is large, and more evenly convex and gradually acquires 
spiral sculpture but no defined peripheral swelling; subsequent whorls 
with about eighteen small but distinct ribs, gradually becoming obso- 
lete at the lower margin, attenuated and arcuate in reverse on the fasci- 
olar surface but not quite attaining the rather distinct cariniform sub- 
sutural collar; on the second body whorl the ribs form acute nodules 
on the peripheral ridge but do not extend materially below the latter, 
and, while still distinct on the fasciolar surface, come still further from 
attaining the subsutural collar; spiral lyrae on and below the peri- 
phery moderately coarse, even, well spaced and without intermediate 
threads, becoming close-set on the beak; on the fasciolar surface they 
are finer and close-set. Length of a specimen of 2 body whorls, 6.4 
mm.; width, 2.0 mm. Lower Claiborne Eocene (from a well seven miles 
south of Jewett, Texas) — Mr. T. H. Aldrich...........bellula n. sp. 
This genus will also include P. georgei Harr., from the 
Lignitic Eocene of Wood’s Bluff, Ala., and an undescribed 
