CONTRIBUTIONS TO PALEONTOLOGY. 71 



CYRTOCERAS JASON ( n. s.). 

 Shell large and strong : outer chamber very deep, uniformly ex- 

 panding towards the aperture ; section somewhat obtusely hexa- 

 gonal, the septate portion round. 



A fragment of the outer chamber, which shows no evidence of 

 septa throughout its entire extent, measures nine inches in length 

 and about three inches in the dorso-ventral diameter; the middle 

 of the side, for a width of nearly an inch and a half, is flattened or 

 depressed convex, and limited by very obtuse or rounded angles : 

 another similar flattened space occupies the ventral slope, and a 

 narrower one the dorsal slope; the ventrum is likewise flattened. 

 The surface is strongly lamellose-striate, and, at irregular intervals, 

 is projected from the sides in lamelliform rings which are deeply 

 sinuate and thickened upon the obtuse angles : there is apparently 

 a row of these upon the dorsum; but this cannot be satisfactorily 

 determined, in consequence of adhering stone. In a length of six 

 inches, there are thirteen of these lamellose extensions. 



A fragment of the septate portion of a specimen, measuring seven 

 inches in length, is two inches in diameter, and has three chambers 

 in the space of an inch. The outer chamber, of nine inches in length, 

 has a deviation from a straight line of one inch; and the septate 

 fragment of seven inches has a deviation of about three inches. 



In surface-characters, this species bears some resemblance to Gyroceras 

 {Cyrtoceras) spinosum; but in that one the striae between the rows of spini- 

 form processes are more undulatory, and, on the ventral side, are regularly 

 undulating, the retral curve being depressed so that the surface is marked 

 by low revolving bands. In a specimen of that species seven inches long, 

 and preserving part of the outer chamber, the curve or deviation from a 

 right line parallel with the outer chamber is five inches and a half. 



Geological formation and locality. In the Schoharie grit : Schoharie. 



CYRTOCERAS MORSUM ( n. s.). ^ A ^. 



A small species in the limestone, with a length of a little more than 

 two inches, has a diameter of a quarter of an inch at the smaller 

 imperfect extremity, and a little over half an inch at the larger 

 extremity : section circular. Surface marked by fine transverse 

 striae, which are aggregated in gently swelling ridges apparently 

 corresponding to the septa. 

 The specimen is too imperfect to be fully characterized. 



1861.] 



