Casey — Notes on the Pleurotomidae. 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 ram. Lower Claiborne Eocene of 

 Lee Co., Texas genii iva n. sp. 



7 — Whorls with two rather widely separated cariuae below 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 cariuae 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. L3ngth of a specimen having 9 

 body whorls, 27 mm.; width, 7.3 mm. Lower Claiborne Eocene of 



Smithsville, Texas margnrilosa n. sp. 



Whorls 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 10 



9 — Embryo forming a regular sharply pointed cone, much higher than wide, 



the upper three or four whorls smooth, the lower two with riblets, 

 those of the basal whorls coarser, those of the one immediately above it 

 very feeble; space between tiie peripheral cariuae and the subsutural 

 usually with a single spiral thread. Length of a specimen having 4 

 body whorls, 9.5 mm; width, 3,2 mm. Jacksonian Eocene of the Red 

 River Kimbrel bed conjancta n. sp. 



Embryo forming a regular sharply pointed cone, much higher than wide, the 

 upper three whorls smooth, very small aud together higher than wide, 

 the three lower having a beautifully regular system of strong close-set 

 equal ribbing, occupying the entire embryo except the very small smooth 

 3-coiled tip; feebly concave surface above the periphery generally 

 having several close-set spiral threads. Length of a specimen having 4 

 body whorls, 8.9 mm.; width, 2.8 mm. L'^wer Claiborne Eocene of St. 

 Maurice, La., and also of Lee Co., Texas [Aldrich] nncleata 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 

 close-set threads. Length of a specimen having 3£ body whorls, 7.7 

 mm.; width, 2.8 m.m. Upper Claiborne ferruginous sands, Ala. 

 {— acutirostris Con . ) childreiii Lea 



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 



