482 Systematic Paleoxtology 



Genus DIAPHOROSTOMA Fischer 



Diapiiorostoma ventricosum (Conrad) 

 Plate LXXXVII, Figs. 1, 2 



Platyostoma ventricosa Conrad, 1842, Jour. Acad. Nat. Sci., Phila., vol. viii, 



p. 275, pi. xvii, fig. 5. 

 Platyostoma ventricosa Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 300, pi. Iv, 



figs. 9a, &, c, d; p. 469, pi. cxii, figs. 1-10; pi. cxiii, figs. 7, 8; pi. cxv, fig. 8, 



1861. 

 Platyostoma ventricosa Nicholson, 1874, Kept, upon the Pal. of the Province 



of Ontario, p. 117, pi. ii, fig. 4. 

 Diaphorostoma ventricosum Clarke, 1900, Mem. N. Y. State Mus., No. 3, vol. 



iii, p. 30, pi. iii, figs. 25-28. 

 Platyostoma ventricosa Weller, 1903, Geol. Survey, N. J., Pal., vol. iii, p. 361, 



pi. xlix, figs. 7-11. 



Description. — " Globose : whorls somewhat scaliform, or flattened 

 above; lower part of columella prominent; labrnm reflected; width and 

 length of aperture nearly equal." Conrad, 184.2. 



" Shell globose or depressed globose and often obliquely ovoid, varying 

 in form. Spire moderately elevated, consisting of three or four volutions, 

 the last of which is extremely ventricose; volutions flattened upon the 

 upper side; aperture circular or subovate; columellar lip reflexed. Sur- 

 face marked by fine closely arranged strige parallel to the lines of growth." 

 Hall, 1859. 



Length of maximum form 7 cm. ; diameter 9 cm. 



This species is very common in the Oriskany of Maryland. Some forms 

 of Platyceras gebhardi bear a strong resemblance to this fomi, but the 

 latter always has an elevated spire which, with the prominence of the lower 

 part of the columella, serves to distinguish the species. 



Occurrence. — Oriskany Formation, Eidgely Member. Cumberland, 

 Hancock, east side Nicholas Mountain, Maryland ; Warren Point, Penn- 

 sylvania; Knobly Mountain, West Virginia. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



[Ohern.] 



Diaphorostoma depressum (Hall) 

 Plate LXXXVI, Figs. 11, 12 



Platyostoma dcprcssa Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 301, pi. Iv. 

 figs. 4a. lb. 



