KTANTON.] 



NATTCIDiE. 137 



Locality and position.— The type was found on Clieycnne river, South 

 I >akota, in strata supposed to belong to the Fort Benton shales. The 

 additional examples above mentioned came from the Pugnellus sand- 

 stone on Williams creek and Poison canyon, Huerfano park, Colorado. 



Genus AMAUROPSIS Morch. 

 Amauropsis bulbiformis Sowerby (sp.). 

 PI. xxx, Figs. 2-4. 



Natica bulbiformis Sowerby, 1832, Trans. Geol. Soc. Lond., 2d eer., vol. in, p. 418, PL 



38, Fig. 13; d'Orb., Pal., Franc., Terr. Cr6t., Gastriropodes, p. 162, PL 174, Fig. 3; 



Goldfuss, Petrofacta Germ., p. 112, PL 199, Figs. 16 and 17; Zekeli, Die Gastro- 



poden der Gosaugebilde, p. 45, PL 8, Fig. 2. 

 Ampulliua bulbiformis Stoliczka, Sitzungsber. k. Akad. d. Wissenscbaften, Wien, 



13d. 52, p. 146; Pal. Indica, Cretaceous Fauna of Southern India, vol. n, p. 300, PL 



21, Figs. 11-15. 

 Compare Amauropsis alveata (Con.) Gabb, Pal. California, vol. i, p. 110, PL 19, Fig. 59. 



Shell large, elongate-ovate, not umbilicate, consisting of seven or 

 eight rapidly increasing, moderately convex, shouldered whorls; spire 

 elevated and prominent, the apical angle varying from about 50° to 

 65°; sutures deeply channeled; aperture elongate- ovate, contracted 

 behind where it is separated from the body of the shell by the chan- 

 neling of the suture, somewhat produced and subangular in front; 

 outer lip thin and sharp; inner lip nearly straight, moderately thick, 

 anteriorly flattened, and reflected so as to form a sharp projecting 

 ridge. Surface marked by lines of growth and by numerous revolving 

 lines of minute punctations that are always visible on well preserved 

 specimens, and on a few examples are situated in well-defined revolving 

 furrows, giving the shell in these rare cases a distinctly striate appear- 

 ance. 



Length of an average specimen, 77 mm ; breadth, 47 ram . The length of 

 the largest specimen in the collection is 92""". 



I have seen no good European examples of this species with which to 

 make direct comparisons, but, judging Irom the published figures and 

 the comments of the authors who have described it, it is quite variable in 

 form, several of the published figures differing more from Sowerby's 

 original drawing than our specimens do. In those in which the aper- 

 ture is represented as complete it is more broadly and regularly 

 rounded than in the shells before me. This and other very slight dif- 

 ferences that might be pointed out do not seem to me sufficient basis 

 for proposing a new name. The species is already known to have had 

 a wide geographic range in Cretaceous time, as it occurs in the Turonian 

 of France, in the Gosau beds of Austria, and in the Cretaceous of 

 southern India, where it is said to range through the entire Cretaceous 

 series developed there. I suspect that some of the California fossils 

 referred by Gabb to Amauropsis alveata really belong to this species, 

 although he states that they are nmbilicated. 



