236 PA I"EO XTOL 00 V OF NE W YO RK. 



septum, and its walls are apparently nearly uniform and straight in its 

 passage through the air-chambers. 



The test, inferring from the crystalline matter remaining on some parts 

 of the surface, has had a thickness of about two mm. Surface marked by 

 irregular, lameilose striae. Internal cast smooth, with the exception of the 

 constriction of the outer chamber, before noticed, and without special eleva- 

 tion or depression of the interseptal spaces. 



This species differs from 0. Pelops, which it closely resembles, in the more 

 gradual expansion of the tube towards the aperture, and in the greater 

 proportional distance of the septa, which are about as five to seven, and also 

 in their greater concavity. In the gradual expansion of the tube, and distance 

 of the septa, it approaches some of the forms in the higher rocks, from which 

 it is otherwise very distinct. See 0. Eriense, plate 40, of the Hamilton group* 

 and O. Atreus, of the Portage group. 



Formation and locality. This species occurs in the upper beds of the Scho- 

 harie grit, near Clarksville, Albany county, N. Y. 



Orthoceras Ohioense. 



PLATES XXXV A, FIGS. 8, 9 ; XXXVI, FIG. 4. 

 Orthoceras Pelops, var. Ohioense, Hai.l. Illustrations of Devonian Fossils: Cephalopoda, pi. 36, fig. 1. 1876 



Shell slightly curved — curvature exogastric. Transverse section circular. 

 Cone regularly and gradually enlarging. Apical angle about 9°. Initial 

 extremity unknown. 



Chamber of habitation large, the portion preserved in an imperfect 

 specimen being about twice as long as its diameter at the base. Aperture 

 unknown, apparently slightly contracted. 



Septa thin, obliquely curved with regard to the axis of the shell, the mar- 

 gins being advanced further forward on the concave or dorsal side of the 

 shell ; in the smaller part of the shell (in the specimen figured), distant about 

 one-sixth, and in the larger portion, near the outer chamber, about one- 

 seventh of the diameter, varying in actual measurement from five to seven 



