INSTITUTE OF SCIENCE, PHILADELPHIA. JOr 



Csecum tortile n. s. 

 Plate 13, figure 9 a. 



Newer Miocene of the Cape Fear River, N. C, at Mrs. Guion's marl-bed, 

 Johnson ; PHocene of the Waccamaw beds at Tilly's Lake, S. C, Johnson ; 

 living twenty-five miles off Cape Hatteras, N. C, in 63 fathoms, U. S. Fish 

 Commission. 



Shell rather large, solid, moderately tapered, slightly twisted, so that it is 

 curved in two directions ; aperture simple, nearly at right angles to the longi- 

 tudinal axis ; posterior margin simple, plug conical, slightly inclined to the 

 right; longitudinal sculpture of numerous sharply incised lines, with wider 

 interspaces, which in passing from the posterior to the anterior margin make 

 as much as one-fourth of a revolution around the shell. Lon. of shell 6.12 ; 

 diam. of anterior end 1.12 ; of posterior end 0.6 mm. 



The amount of twist varies considerably in different specimens ; some 

 show very little, but in the best-preserved specimens it sometimes reaches one- 

 quarter of a revolution. The following species is the only one which ap- 

 proaches C. tortile, apart from the torsion. 



Caecum (tortile var. ?) ibex n. s. 

 Plate 20, figure 10 a. 



Newer Miocene of the Cape Fear River, N. C, at Mrs. Guion's ; Pliocene 

 of the Waccamaw beds at Tilly's Lake, S. C, Johnson. 



Shell resembling C. tortile, except in the following particulars : it is 

 slightly more slender, with fewer and coarser ribs, which are separated by per- 

 ceptible channels, across which the lines of growth are rather strong, giving 

 the shell a faintly reticulated aspect; the anterior aperture is slightly con- 

 tracted and the external edge bevelled ; the form is slightly more conical. 

 Max. lon. of shell 5.5 ; diam. of anterior end 0.8 ; of posterior end 0.4 mm. 



The shells sometimes, like nearly all the elongated and longitudinally 

 sculptured Caecids, exhibit a moderate amount of torsion, but most of them 

 are straight. C. Stevensoni Meyer is a similar species, but smaller, shorter, and 

 with annulations often visible near the extremities. 



Genus MBIOCBRAS Carpenter. 



Meioceras Cpr., P. Z. S. 1858, p. 26. 



Inflaiulum Cpr., Mazatlan Cat. B. M., p. 314, note ; ex parte. 



Bovicornu Meyer, Ala. Geol. Rep., p. 79 (under Pteropodd) 1886. 



The species of this group cannot be determined from the shell in its 

 younger stage, as individuals vary considerably. 



