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NEW YORK STATE MUSEUM 



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majority of the specimens having 14 thecae in 10 mm even in the mature 

 parts. But the most conspicuous difference from the typical C . ty p i - 

 calis is the presence of the two straight, thin spines reminding of the 

 sicular spines of C . bicornis. There are no such lateral spines observ- 

 able on an)' of the multitude of specimens of C . t y p i c a 1 i s covering the 

 slabs of Utica shale in the Mohawk valley or on those from the Cincinnati 

 beds, while they are clearly a constant character in the Saratoga county 

 specimens. 



But the best preserved of the Cincinnati specimens of C . typicalis 

 show a thin needlelike virgella and a mucro at the 

 opposite side of the sicular aperture [see text fig. 361]. 

 The two spines of our mutation are now quite clearly, 

 from their angle of divergence and their place of inser- 

 tion further prolongations of these sicular spines, hence 

 not homologous at all to the two lateral spines of 

 C . bicornis, which grow from the first two thecae. 

 The question could arise whether since Hall's first 

 figure of C . bicornis represents a specimen belong- 

 ing to this mutation, the latter should not be considered 

 the type of C . bicornis, but the reading of Hall's 

 Fi ? . 363. ciimacogra^tus original description will convince any one that he took 



typicalis mm. spinner b i ' 



nov. Sicular end of rhabdosome. , tvt i-iir r 1 • 1 r /— l • 



x 5 the Normanskul form for the typical one ot L . bicor- 



n i s and his later erection of the species C . typicalis corroborates this 



view. No confusion can, therefore, be possibly caused by referring this 



first figure of C . bicornis to the mutation of C. typicalis where it 



properly belongs. For the latter we propose the name C . typicalis 



var. spinifer. The exact horizon at which it occurs has not yet been 



established. 



Climacograptus ulrichi sp. nov. 



Plate 28, figures 10, n 



Description. Synrhabdosomes not observed. Rhabdosomes small 

 (12-18 nun). Sicular end as in C. typicalis, narrow and acutely 

 pointed, furnished with short stout virgella and an opposite, parallel, sicular 



