824 SYSTEMATIC PALEONTOLOGY 



ORTHOCEKAS TEANSVEESUM Miller 

 Plate LV, Fig. 27 



Orthoceras transversum Miller, 1875, Cincinnati Quart. Jour. Sci., vol. ii, 



p. 129. 

 Orthoceras transversum Miller, 1889, North. Amer. Geol. Pal., p. 452, text 



fig. 755. 



Description. "Shell medium size, rather rapidly enlarging; septa 

 strongly arched and distant about one-fourth or one-fifth the diameter 

 of the shell ; siphuncle excentric, its form not observed ; outer shell thin 

 and marked by strong transverse lines, distant from l-100th to 4-100ths of 

 an inch in a specimen having a diameter at the large end of three-fourths 

 of an inch. The distance between these lines seems to increase as the 

 diameter of the shell increases, but their distance apart is not uniform in 

 different specimens of the same size. About four or five of these trans- 

 verse lines will mark the distance between the septa, though they do not 

 seem to have any connection with the arrangement of the latter" 

 Miller, 1875. 



The well-marked transverse lines of this species cause its recognition 

 to be quite easy. 



Occurrence. MAETINSBUEG SHALE (Eden division). Jordans Knob, 

 one and one-half miles northeast of Fort Loudon, Pennsylvania; and 

 Eickard Mountain, Washington County, Maryland. Eden shale at Cin- 

 cinnati, Ohio. 



Collection. U. S. National Museum. 



OETHOCERAS LAMELLOSUM Hall 

 Plate LVIII, Figs. 5, G 



Orthoceras lamellosum Hall, 1847, Pal. New York, vol. i, p. 312, pi. Ixxxvi, 

 figs. 2a-e. 



Description. Shell slender and gradually tapering ; septa distant from 

 each other one-fifth to one-fourth of an inch and having a convexity about 

 equal to their distance apart; siphuncle slightly excentric; surface 

 apparently lamellose or subimbricate. 



