UTICA SLATE AND HUDSON-RIVER GROUP. 265 



GRAPTOLITES OF THE UTICA SLATE AND HUDSON-RIVER GROUP. 



The fossils of this genus are numerous in many localities of the Utica slate, as well as 

 in the succeeding greenish or olive shales. In the same shales and slates along the Hudson 

 river, they are more numerous, both as individuals and species, than in any other part of 

 the State, or perhaps of the Continent. This genus, which recently contained but a few 

 species, has become so augmented that it now numbers not less than twenty distinct 

 forms. In consequence of these fossils being usually imbedded in shale, and often 

 extremely compressed, some doubt of their true nature has been entertained, and by 

 some authors they have been placed among plants. When imbedded in calcareous matter, 

 they ofJen preserve their original form and proportions, and reveal more clearly their 

 true character. In this condition, they show a more close analogy with the Linnean 

 ViRGULARiA than with any other among living forms. This opinion has already been 

 advanced by Dr. Beck of Copenhagen ( Murchison, Sil. System, p. 695 ) ; and an inspec- 

 tion of the figures of G. bicomis, from specimens in limestone ( Plate LXXIII, figs. 2 

 m and m' ) , will sustain this view. Judging from this and several other well preserved 

 specimens, all the Graptolites possessed a semicalcareous body with a corticiform 

 covering ; which latter, entirely compressed, is all that is usually preserved in the slates. 



32], 2. GRAPTOLITHUS PRISTIS. 



Pi- LXXII. Fig3. 1 o - ». 



Prionotia prittis. HisnroCB, Leth. Suecica, 1837, pag. 114, pi. 33, sup. fig. S. 

 Compare Graptolithut foliaeeua, Murchison,* Sil. System, 1839, pi. 26, fig. 3. 



"Linear, straight, scarcely a line broad, compressed ; rachis central, capillary ; both sides 

 with broad acute teeth." 



This description of Hisinger corresponds precisely with the most abundant and widely 

 distributed species of this genus which we have in the older slates. The species occurs in 

 small short fragments, and in forms which appear to be nearly entire, having a length of 

 two inches. When the specimens are flattened, a central capillary axis is very perceptible, 

 extending the entire length. In some specimens where the serrated portion is removed, 



• PoBTLocK is inadvertentiy cited an authority for this species, on page 79 of this volume. 

 I PaljEontologt.] 34 



