CONTRIBUTIONS TO PALAEONTOLOGY. 79 



adjacent to the outer chamber. A fragment two inches long and nearly 

 three-fourths of an inch in diameter at the larger end, and less than half 

 an inch at the smaller end, has somewhat more than eight annulations. 



Geological formation and locality. In the soft shales of the Hamilton 

 group : on the shore of Seneca lake, and at Ludlowville on Cayuga lake ; 

 and in the coarser shales at Cazenovia, Hamilton, and other places in New- 

 York. 



ORTHOCERAS NUNTIUM ( n. s.). ^/- ^^ > Y 



Shell somewhat slender, very gradually tapering from the outer 

 chamber : septa convex, the convexity nearly equal to twice the 

 distance between the septa; siphuncle small, central. 



Surface annulated by about one annulation to each septum; and 

 the fine thread-like longitudinal strise are crossed by fainter 

 transverse striae, which are more conspicuous near the aperture, 

 but often scarcely visible on well-preserved specimens. 



A specimen a little less than half an inch in diameter at the larger 

 end, has sixteen annulations in the length of an inch and a half. Two other 

 specimens, of about half an inch in diameter, have nine or ten annulations 

 in the length of an inch. A specimen a quarter of an inch in diameter at 

 the smaller end, has over thirteen annulations in the length of an inch. The 

 annulations are slightly oblique to the axis ; but in a well-marked specimen, 

 are limited to a single division, being on one side at the upper margin, and 

 on the opposite side at the lower margin of the chamber, making the obli- 

 quity equal the distance between two septa. 



This species is less rapidly attenuate than the preceding ; the annulations 

 sharper, and twice as numerous on specimens of the same size. The nume- 

 rous annulations, and their relations to the septa, are distinctive characters. 

 The shell tapers less rapidly than 0. crotalum. 



This and the preceding species bear a very close relation to O. ibex (So- 

 werby), or 0. ibex and O. articulatum as united ; but I am unable to 

 identify them satisfactorily. 



Geological formation and locality. In the soft shales of the Hamilton 

 group : on the shores of Seneca lake ; and in the coarser shales east of 

 Cayuga lake. « 



1861.] 



