INSTITUTE OF SCIENCE, PHILADELPHIA. 255 



Transitions will be found between these different groups whenever a 

 sufficiently large series is examined. 



The angle at which the sinistral tip is inclined is not absolutely con- 

 stant, even in the same species, but in general is nearly at right angles to the 

 axis of the adult shell. The larval whorls, so far as yet observed, are always 

 smooth ; the ribs are usually more pronounced toward the apex, if not uniform ; 

 but the spiral sculpture, if variable, tends to be stronger on the later whorls ; 

 from which we may surmise that the ancestors of the group were smooth, 

 that the axial ribs were subsequently acquired, while the spiral grooving is, on 

 the whole, a still later development. 



Pasitliea lugubris Lea, P. secale Lea, and /-". elegans Lea, from the Clai- 

 bornian, are probably referable to this genus. 



Turbonilla virgata Dall. 



T. exarata Holmes, Post-Pl. Foss. S. Car., p. 82, pi. xiii. figs. 2, 2 a, 2 b, 1859 ; as of H, C. 



Lea, 1S45. 

 Not Pasitliea exarata Lea, Trans. Am. Phil. Soc. ix., extras p. 25, pi. 35, fig. 44, 1S45. 



Later Miocene of North Carolina at Mrs. Purdy's marl-bed on the Cape 

 Fear River, Johnson ; Pliocene of the Caloosahatchie beds and the Myakka 

 River, Florida, Dall and Willcox ; living from North Carolina to Florida in 

 12 to 80 fathoms, U. S. Fish Commission and other collectors. 



This species resembles T. nivea Stm., but has more numerous, slender and 

 oblique ribs, which cease at the periphery. The pillar is straight, especially in 

 the young, and none of the specimens show any plait. It does not appear to 

 be identical with Lea's species from the Virginia Miocene, to which it was 

 referred by Holmes. Some fragments from the Waccamaw beds may be 

 referable to this species. 



Turbonilla nivea Stimpson. 



Cliemnitzia nivea Stm., Proc. Bost. Soc. Nat. Hist. iv. p. 114, 1851 ; Shells of N. E., p. 



40, iSsr. 

 Turbonilla nivea Stm., S. I. Checklist of Sh., 1865 ; Binney's Gould, p. 331, 1870 (figure 602 



excluded); Holmes, Post-Pl. Foss. S. C, p. 83, pi. xiii. figs. 3, 3 a, 3 b, 1859. 



Pliocene of the Waccamaw beds, N. Carolina, Johnson ; Post-Pliocene of 

 John's Island, Cainhoy and Simmons's Bluff, South Carolina, Holmes; living 

 from Eastport, Maine, to the Carolinas. 



The figure given by Binney does not represent this species and does not 

 agree with Stimpson's types in the National Museum. Holmes's specimens 

 were partly identified by Dr. Stimpson, and his figure agrees with authentic 

 specimens. The species has been distributed by the late Col. E. Jewett, 

 under the erroneous name of " T. gracilis De Konig." 



A few worn fragments from Tilly's Lake appear to be referable to this 

 species. They do not show any plait on the pillar. 



