48 The Fauna of the Keyser Member oe tije 



qass cephalopoda 



Subclass TETRABRANCHIATA 



Order NAUTILOIDEA 



Suborder ORTHOCHOANITES 

 Family ORTHOCERATIDAE 



Genus ORTHOCERAS Breyn 



Ortiioceras schucherti u. sp. 

 Plate LXXXVIII, Fig. i 



Description. — Shell subeylindrical, tapering very gradually; septa con- 

 vex, siphuncle not observed. Surface marked by numerous simple rounded 

 somewhat abruptly elevated concentric annulations, at least five occurring 

 in the space of 10 mm. Surface too badly weathered to observe any trans- 

 verse or longitudinal strias if present. 



This species closely resembles Oriliocems t e nv i annul aium (Hall) of 

 the Helderberg. It may be distinguished, however, by its smaller apical 

 angle and by possessing shallower and more numerous annulations. 



Occurrence. — Helderberg Formation, Keyser Member. Cumber- 

 land. 



CoUection. — U. S. National Museum. 



Ortiioceras rigidum Hall? 

 Plate LXXXVIII, Fig. 5 



Ortiioceras rigidium Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 344, pi. Ixx, 

 figs. 3a-d, 1861. 



Description. — "Shell elongate, gradually tapering; section circular. 

 Septa moderately convex, distant from each other about one-sixth the 

 diameter of the tube. Siphuncle central, narrow in its passage through 

 the septum. Surface marked by fine sharply elevated equal transverse 

 striffi." Hall, 1859. 



Occf/rrence.— Helderberg Formation", Keyser Member. Devil's 

 Backbone. 



Collection. — Maryland Geological Survey. 



