300 PROCEEDINGS OF THE ACADEMY OP [Sept., 



sculpture barely visible to the unaided eye, axial sculpture restricted 

 to strong and conspicuous incremental lines, occurring at irregular 

 intervals, and to low, obscure and unequal axial wrinkles on the 

 periphery of the whorl; spiral sculpture microscopically fine but 

 sharp, consisting of about fifteen closely spaced feebly impressed 

 lines to each of the whorls of the spire, but about thirty-five on the 

 sides and base of the body; suture simple and appressed, posterior 

 edges of whorls very sharp in front of suture; peripheral angle obtuse, 

 base of body broadly rounded; aperture holostomous, obliquely 

 ovate, angulated at the posterior commissure; outer lip rounded 

 and slightly effuse at the anterior, its curvature higher than that 

 of the inner lip; inner lip smoothly glazed and reflected concealing 

 the umbilical chink; parietal wash thin, columella smooth. 



Dimensions. — Altitude 31.5 mm.; maximum diameter 9.9 mm. 



Only one shell of this species is known and this individual aside 

 from the loss of its apical tip is as strong and well preserved as if it 

 were a recent shell. Chemnitzia cerithiformis Meek and Hayden^^ 

 from the Fox Hills group of the Upper Missouri Cretaceous no doubt 

 belongs to the same genus. In 1860, Meek and Hayden^- in a check 

 list referred this species to the genus Scala (Acirsa) but in their final 

 description it was assigned to the genus Chemnitzia. After a study 

 of Cossmann's very comprehensive work on the Scalidse^^ and three 

 species, including Chemnitzia cerithiformis, recently collected from 

 Coon Creek, it seems that Meek and Hay den's species was an Acirsa 

 and that the other two Tennessee species are congeneric. 



Acirsa corrugata n. sp. PI. XVIII, fig. 9. 



Description. — Shell small and slender; form elongate-conic, spire 

 acuminate; whorls eleven in number, slightly convex and increasing 

 in size regularly and very slowly; protoconch scar small; sculpture 

 elaborate, consisting of both axial and spiral elements; axial eleva- 

 tions strong and crowded on the early whorls of the spire, but becoming 

 lower and more widely spaced on the later volutions; spiral sculpture 

 overriding the axials, but very obscure on their summits; spiral sculp- 

 ture consisting of low, crowded thread-like lirae, sixteen to twenty in 

 number on the later whorls of the spire and with slightly wider 

 additional spirals on the base of the body; interspiral areas marked 

 b}^ very fine and regular pittings; suture distinctly impressed; 



« Meek and Hayden, 1876, U. S. Geol. Survey of the Terr., Vol. IX, p. 339, 

 PL 32, figs. 10a, b. 



"' Meek and Hayden, 1860, Proc. Acad. Nat. Sci. Puila., XII, p. 185. 

 "s Cossmann, M., 1912, Ess. de Pal. Comp., pp. 16-102. 



