Casey — Notes on the Plewrotomidae. 135 
Peripheral double carina distinctly below the middle of the whorls, broader, 
the denticulation coarser and more close-set; form not quite so slender 
though about equal in length to rotaedens; aperture and canal com- 
bined more than a third of the total length. Length of a specimen having 
6 body whorls, 11.5 mm.; width, 3.4 mm, Lower Claiborne Eocene of 
hee: Cou, TERA 6a) caeren es oes Neo <s else ncaa ssicS abs s PONILVA IN. SDs 
7 — Whorls with two rather widely Seated carinae Balen the suture; em- 
bryo relatively small in size, somewhat higher than wide, with about three 
small smooth apical whorls, gradually increasing as usual, and two 
whorls covered with coarse and rather widely spaced riblets; peripheral 
duplex carina not strongly elevated, the space between it and the lower 
and larger of the subsutural carinae about twice as wide as the peripheral 
baud and having two spiral threads and sometimes three other smaller 
ones in addition; space below the periphery with several spiral carinules; 
shell rather large, the beak straight but somewhat feebly, obliquely 
swollen toward tip; length of the aperture and canal together nearly 
two-fifths the length of the shell. Length of a specimen having 9 
body whorls, 27 mm.; width, 7.3 mm. Lower Claiborne Eocene of 
SmMibhsvillé Texas ce cic. ssicie aeeeeels sinsieate ness sees MAT ERritOss, 0. Sp. 
Wohorls with a single subsutural carina; species very small in size........8 
8 — Embryo large, much higher than wide and elaborately sculptured..... 9 
Embryo smaller, about as high as wide, with three smooth rapidly increas- 
ing apical whorls and two basal covered with the usual riblets.......19 
9 — Embryo forming a regular sharply pointed cone, much higher than wide, 
the upper three or four whorls smooth, the lower two with riblets, 
tbose of the basal whorls coarser, those of the one immediately above it 
very feeble; space between the peripheral carinae and the subsutural 
usually with a single spiral thread. Length of a specimen baving 4 
body whorls, 9.6mm; width, 3.2mm. Jacksonian Eocene of the Red 
River Kimbrel bed.......2 eee cece seoecee sooeveeeeCONjUNCtA D. Sp. 
Embryo forming a regular sharply pointed cone, much higher than wide, the 
upper three whorls smooth, very small and together higher than wide, 
the three iower having a beautifully regular system of strong close-set 
equal ribbing, occupying the entire embryo except the very small smooth 
8-coiled tip; feebly coucave surface above the periphery generally 
having several close-set spiral threads. Length of a specimen having 4 
body whorls, 8.9 mm.; width, 2.8mm. Lower Claiborne Eocene of St. 
Maurice, La., and also of Lee Co., Texas [Aldrich]....-nucleata n. sp. 
Embryo large, much higher than wide, the lower three whorls subcylin- 
drical and covered with fine arcuate and rather widely spaced riblets, 
the upper smooth part consisting of two or three whorls very rapidly 
diminishing in size and together much wider than high; moderately 
concave surface above the duplex peripheral carina usually having two 
elose-set threads. Length of a specimen having 34 body whorls, 7.7 
mm.; width, 2.8 m.m. Upper Claiborne ferruginous sands, Ala. 
(= acutirostris COD.) .s.s.seee scenes pid’eiel sidivristobie dan e's COMIGTONE en 
10 — Denticulation of the duplex peripheral carina unusually small and 
widely spaced, the concave surface, between the periphery and subsu- 
tural carinule usually with two fine spiral threads; beak nearly 
straight, very slender, the aperture and canal combined but little less 
