1917.] NATURAL SCIENCES OF PHILADELPHIA. 297 



Shell fairly large and simple, elongate conical; spire elevated and 

 acute; aperture less than one-third as high as the entire shell; whorls 

 of conch numerous, flattened and wide, increasing in size regularly 

 and slowly; protoconch small and trochoid, coiled about three times, 

 line between the conch and protoconch poorly defined; external 

 surface usually smooth and glazed; sculpture absent and subdued; 

 incremental varices occasionally present; suture simple and distinct; 

 body abruptly constricted in front of the periphery into the short, 

 curved pillar; aperture lenticular, angular behind and produced in 

 front into a short canal; outer lip thin and simple; inner lip excavated; 

 parietal wall glazed; columella smooth. 



This genus is proposed to include a group of gastropo'ds charac- 

 terized by simple, elongate-conical shells with unadorned external 

 surfaces. The aperture is subovate, considerably narrowed toward 

 each end, terminating anteriorly in a short canal. Besides the type, 

 two other species are known, one of which was described under the 

 name of Cerithium {Fibula f) detedum^^ by Stoliczka from the Arria- 

 loor group of beds from the Upper Cretaceous of South India: the 

 other under the name of Pseudomelania astonensis^^ by Huddleston 

 from the upper division of the Inferior Oolite of England. Nudivagus 

 differs from Cerithium, however, in the character of the aperture and 

 in the absence of a strongly twisted columella and from Clava in 

 having a non-plicate columella. Nudivagus is probably near Gymno- 

 cerithium^^ but differs from the latter in having less numerous whorls 

 which are of greater height and less convexity. The new genus 

 differs from Pseudomelania in the presence of an anterior canal. 

 Meek's genus Closteriscus^^ includes elongate-conical forms somewhat 

 similar to Nudivagus in outline and lack of external ornamentation, 

 but the former, however, possesses well defined tooth-like, internal 

 varices not found in the body cavities of the latter. 



Nudivagus simplicus n. sp. PI. XIX, figs. 4, 5. 



Description. — Shell fairly large and simple; thick but very friable, 

 outline elongate-conical; spire elevated and acute, its elevation more 

 than twice as great as the length of the aperture; whorls ten in num- 

 ber, closely appressed; obliquely flattened, increasing gradually and 



'2 Stoliczka, F., 1868, Geol. Survey of India, Pal. Indica, Cret. Faunas Southern 

 India, Vol. II, p. 192, PI. XV, fig. 1. 



33 Huddleston, W. H., 1896, Pal. Soc. London, Monogr. Inferior Oolite, Gastro- 

 poda, p. 245, PI. XVIII, figs. 8a, b. 



34 Cossmann, M., 1906, Ess. de Pal. comp., livr. VII, p. 36, PI. VII, fig. 17. 



35 Meek and Hayden, 1876, U. S. Geol. Survey of the Terr., Inv. Pal. Vol. IX,. 

 p. 306. 



