Casey — Notes on the Pleurotomidae. 131 
sinus, and a conspicuous system of lines of growth, bi- 
oblique toward the peripheral carina and composed of exca- 
vated lines, which are less evident in the very early forms 
and most conspicuous inthe modern species. The type is P. 
cochlearis Con. of the Vicksburg Oligocene. Pleuwroliria 
comprises two groups, which, although strongly resembling 
each other in general form and type of sculpture, are in reality 
almost subgeneric in value as shown below: — 
Group 1.— Embryo multispiral and acute. 
Lines of growth less pronounced, uneven and never deeply incised; species 
small in size and older geolOgicall y....-s.se rece ee eeee rece ceees Snape 2 
Lines of growth deeply incised and CONSPICUOUS... -seeeeeeereesererees 3 
2—Shell rather slender, each of the spire whorls with a moderate sub- 
sutured carina, the surface immediately below it being concave and 
rather rapidly expanding to a stronger peripheral carina perfectly 
smooth and uniform, and situated at some distance above the middle, the 
surface thence cyclindric or very feebly descending to the suture below 
and having two slightly smaller and somewhat approximate carinae at the 
middle, the lower margin also carinulate. The two carinae below the 
periphery become more widely separated on the larger whorls, sub- 
equally trisecting the space between it and the lower margin, and, on 
the body whorl, continue thus unaltered to the base of the shell. The 
concave surface above the periphery has a fine spiral thread above the 
middle. Embryo moderately stout, conical, closely coiled, rather 
higher than wide, with five whorls, the four upper smooth, broadly, 
evenly convex and polished, the lowermost with longitudinal riblets; 
beak moderately long, the aperture proportioned nearly as in cochlearis. 
Length of a specimen having 5 body whorls, 9mm.; width,2.7 mm. 
Lower Claiborne Eocene of St. Maurice, La..... -.+e---Simplex n. sp. 
Shell nearly as in the preceding but with the embryo shorter and stouter, 
fully as wide as high and not eveuly conical but becoming substyliform 
toward the very acute tip, of five whorls, the lowermost covered with 
riblets. Spire whorls shorter; carinae below the periphery more equal 
and close-set, the peripheral carina finely, obtusely crenulate. Length 
of a specimen of 2 body whorls, 3.4 mm.; width, 1.2mm. Lower Clai- 
borne Eocene of St. Maurice.....c+s+.----- >eeeeee-+e-Crenulosa n. sp. 
3 — Embryo of four whorls, evenly conical, short, fully as wide as high, the 
upper three whorls smooth polished and broadly convex, the lowermost 
bearing acute but rather widely spaced longitudinal riblets. Shellrather 
short and stout, with slender beak, the spire whorls very short, each 
with two strong thick and equal carinae, one just below the suture, the 
other near basal third; between the latter and the basal margin there is 
a fine spiral thread first appearing on about the third whorl; lines of 
growth only moderately distinct and somewhat irregular. Length ofa 
specimen having 3 body whorls, 4.5 mm.; width1.7 mm. Jacksonian 
Eocene of Montgomery, La........+seeseeee+  eeeeee Jacksonella nu. sp. 
