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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. bilineatum^ 

 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, i mm 

 in 12 or 13 mm. The section is 

 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 they 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 flat, their depth mostly not 

 reaching • 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 [sec 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, 



C": 





tja 



Fig. 17a Protocycloceras whit- 

 fieldi sp. nov. Longitudinal section. 

 Natural size. Fig. ij/> Enlargement of 

 the ectosiphuncle of the same, x 3 



