28 A COXTRIBUTIOX TO THE LoWER DeYOXIAX FaUXAS OF MaEYLAXD 



scription. In general aspect it is not unlike H. antiqua, but any attempt 

 at further identification is hazardous till further collections are made. 



Occurrence. — Helderbkeg Formatiox. Cumberland. 



Collection. — George M. Eoeder. 



HOLOPEA sp. 



Plate LXXIX, Fig. 9 



Description.— The large specimen figured represents a form which is 

 referred with doubt to this genus. A part of the body whorl has been 

 broken off, all surface features have been obliterated and the whole shell 

 laterally compressed, thus making identification impossible. The writer 

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



Length -i cm.; diameter 3.2 cm. 



Occurrence. — Helderbekg Formatiox. Cumberland. 



Collection. — George M. Eoeder. 



Genus ORTHONYCHIA Hall 



Ortiioxychia tortuosa (Hall) 

 Plate LXXTX, Figs. 10-12 



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



figs. 1-5, 1861. 

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

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



pi. xlix, figs. 13-17. 



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

 free volution : volutions widely separated, very gradually increasing in 

 size towards the aperture, which is scarcel}' expanded; peristome very 

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

 Hall, 1859. 



Surface marked by irregular, undulating lamella?, the undulations evi- 

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

 observable on the interior of the spire. 



Lenirth 5 cm. ; maximum diameter !^ cm. 



