UTICA SLAtE AND HUDSON-RIVEK GROUP. 271 



326. 7. GRAPTOLITHUS SCALARIS. 



Pl. LXXIII. Figs. 4a-g. 



Graptolithua tcalarit. Linne. 



Prionotiu acalaris. Hisingeb, Leth. Suecica, Supplement, 1837, pag. U5, pl. 35, fig. 4 a J. 



Linear, straight, rigid, compressed, with a capillary central axis ; margins smooth ; spaces 

 on each side of the axis marked by transverse slits or dissepiments, which do not reach the 

 margin ; stipe narrowing towards the base, and terminating in a thickened expansion. 



This appears to be identical with the figure and description of Hisinger. I have other 

 specimens which show no central axis, and have but a single range of transverse dissepi- 

 ments ; these I have arranged with the former, believing that this difference is due to 

 accidental causes, or to one side of the specimen only being shown. 



This species is more rigid than either of the preceding, except G. bicornis, and is readily 

 distinguished by the absence of serratures on either margin. 



Fig. 4 a. A specimen showing the radical termination. 



Fig. 4 ft. A portion of the same magnified. 



Fig. 4 c. A more slender and tapering specimen, with a single range of dissepiments. 



Fig. 4 i. A portion of the same magnified. 



Fig. 4 «,/ A small fragment, with oblique dissepiments and smooth margins. This resembles the G. 



sagiltarius, with both margins uninterrupted. 

 Fig. 4 ^. A specimen with, apparently, a single range of dissepiments, and a central capillary axis 



projecting beyond the stipe. 



The forms given are quite variable, possessing a single character in common, that of 

 continuous smooth margins. The specimens are all exceedingly compressed, and it appears 

 as if the apparently continuous margin may be fallacious, or due to the expansion of the 

 thin covering of the stipe beyond the edges of the serrae. This conclusion appears more 

 reasonable when we compare the nearly direct and oblique dissepiments, corresponding to 

 the G. bicornis and G. Sagittarius. The same character has been observed by Capt. Portlock 

 (id dt., pag. 321, pl. 20, figs. 2, 3 and 4) . I cannot doubt but this one ( represented in 

 fig. 4 a, b) is the form to which Hisimger applies the name of Prionotus scalaris. 



Position and locality. This species, fig. 4 c, occurs in the Utica slate, on West-Canada 

 creek. The other specimens figured were all obtained from the Norman's kill, near Albany. 



(State Collection.) 



