332 NEW YORK STATE MUSEUM 



We have preferred to consider this form as a full species for several 

 reasons, the principal one of which is that there exists again a distinct and 

 characteristic variety of it in D. spinifer van geniculatus, which 

 fact indicates the thoroughness of the final separation of D. spinifer 

 and D . ramosus, 



Position and localities. In the Normanskill shale at Mt Moreno but 

 one or two fragments of r a m osus have been observed, while this species 

 is there the dominant form of one of the layers [sec plate 22]. It is there 

 associated with Climacogr. par v u s and L as i o g r. m u cronat u s. 

 It is also the prevailing form at Glenmont, from where I have before me a 

 specimen, one of whose fragmentary uniserial branches reaches the remark- 

 able length of 164 mm. It is associated with Climacogr. parvus, 

 L a s i o g r. mucronatus, D i c e 1 1 o g r. g u r 1 e y i, etc. There are also 

 a few specimens from the Stockport collection referable to this species. 



Finally the specimens from the Utica shale at Oxtungo creek, a 

 southern affluent of the Mohawk river, which have been referred by 

 Whitfield and Gurley to D. ramosus, represent quite evidently a late 

 mutation of this type ; for they possess the fusiform biserial portion, the 

 somewhat greater angle of bifurcation of the branches [sec pi. 23, fig. 2] and 

 also the mesial spines can be seen in spite of the poor preservation of the 

 old museum specimens to which the above mentioned authors had reference. 

 The biserial part of the rhabdosome is not longer than in ramosus. 

 These specimens are associated with Leptobolus i n s i g n i s and 

 Climacogr. t y p i c a 1 i s. 



A slab of the museum collection, ticketed as Utica shale and of 

 unknown locality, bears besides the Utica mutation of Climacogr. 

 typical is and Corynoides curt us var. comma large ami typical 

 specimens of D. spinifer, identical in their characters with the Mt 

 Moreno individuals. 



In Great Britain this form occurs in S. Scotland in the Glenkiln and 

 Lower Hartfell shales (Balclatchie beds). 



