Maryland Geological Survey 469 



laterally compressed, thus making identification impossible. The writer 

 is very much in doubt as to the horizon to which this specimen belongs. 

 Length 4 cm. ; diameter 3.2 cm. 



Occurrence. — Helderberg Formation. Cumberland. 

 Collection. — George M. Boeder. 



[Ohern.] 

 Genus ORTHONYCHIA Hall 



Orthonychia toktuosa (Hall) 

 Plate LXXIX, Figs. 10-12 



Platyceras tortuosum Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 472, pi. cxiii, 



figs. 1-5, 1861. 

 Orthonychia tortuosa Clarke, 1900, Mem. N. Y. State Mus., vol. iii, No. 3, p. 30. 

 Platyceras tortuosum Weller, 1903, Geol. Survey N. J., Pal., vol. iii, p. 362, 



pi. xlix, figs. 13-17. 



Descnption. — " Shell spirally ascending, making a little more than one 

 free volution : volutions widely separated, very gradually increasing in 

 size towards the aperture, which is scarcely expanded; peristome very 

 oblique. A broad spiral fold sometimes marks the inner side of the spire." 

 Hall, 1859. 



Surface marked by irregular, undulating lamellae, the undulations evi- 

 dently marking the position of sinuses. As high as three distinct folds are 

 observable on the interior of the spire. 



Length 5 cm. ; maximum diameter 3 cm. 



Occurrence. — Oriskany Formation, Eidgely Member. Devil's Back- 

 bone, Hancock, Knobly Mountain near Cumberland. 



Collections. — Maryland Geological Survey, Maryland Academy of 

 Sciences. 



[Ohern.] 

 Genus PLATYCERAS Conrad 



Platyceras nodosum Conrad 



Plate LXXIX, Figs. 13, 14 



Platyceras nodosum. Conrad, 1841, Ann. Rept. Pal. N. Y., p. 56. 



Platyceras nodosum Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 473, pi. cxv, 



figs. 1-6; pi. cxvi, figs. 1-4, 1861. 

 Platyceras nodosum Clarke, 1900, Mem. N. Y. State Mus., No. 3, vol. iii, p. 31. 



