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NEW YORK STATE MUSEUM 



nent author. Our own observations do not warrant such con- 

 servatism but demonstrate the Fort Cassin, as well as the annu- 

 lated Isle La Motte types to be different from O . b i 1 i n e a t u fn . 

 As a matter of fact they even belong to different genera. In describ- 

 ing here the Fort Cassin form as new we take particular pleasure 

 in naming it after Prof. Whitfield, who has so 

 carefully described and figured the Fort Cassin 

 fauna. 



Description. Slender orthoceracone of rather 

 small size. The specimen figured by Prof. Whit- 

 field has a length of 84 mm, but lacks living- 

 chamber and apical portion and indicates an 

 original length of the individual, at least three 

 times that of the fragment. The greatest width 

 of the fragment is 25 mm. The rate of growth 

 of the conch is very small, 1 mm 

 in 12 or 13 mm. The section is 

 .CJ^; circular. The outer wall possesses 



concentric annulations which are 

 mostly rather oblique or undulat- 

 / ing, in exfoliated specimens they 



( appear as ridges with rounded 



edges, but on the surface the}- were 

 more sharply elevated and angular. 

 They are closely arranged, exactly 

 corresponding in interval to the 

 depth of the chambers, the sutures 

 falling into the interspaces, which 

 are of equal width with the ridges and uniformly concave. There 

 are 5 of these annulations in the space of 20 mm, where the diam- 

 eter of the conch is approximately 20 mm. 



The cameras are very shallow, there being counted 5-6 in the space 

 of 20 mm, the sutures pass obliquely or undulating around, the 

 same as the annulations; the septa are fiat, their depth mostly not 

 icaching and never surpassing that of the cameras. The living 

 chamber has not been observed. The siphuncle is large, one third 

 the width of the conch, tubular and situated slightly excentrically in 

 such a way that its inner margin coincides approximately with the 

 axis of the conch [see text fig. 17]. 



The surface on the fragments observed is marked with fine en- 

 circling lines only and lacks longitudinal ridges. 



Position and locality. In the Fort Cassin beds at Fort Cassin. 



Fi 



Protocycloceras whit- 

 sp. nov. Longitudinal section. 

 Natural size. Fig. 17/* Enlargement of 

 the ectosiphuncle of the same. X3 



eld 



