

a. 



UTICA SLATE AND ilUDSON-RIVEH GROUP. 205 



GRAPTOLITES OF THE UTICA SLATE AND HUDSON-RIVER GROUP. 



Tlie fossils of (his genus are numerous in many localities of tlie 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, hoth as individuals and species, than in any other part of 

 the State, or perhaps of the Continent. This genus, which recently contained Init 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 j)lnced among plants. When imltedded in calcareous matter, 

 they often preserve their original form and proportions, and reveal more cleaily their 

 true character. In tliis 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. bicornis, from specimens in limestone ( Plate LXXIII, figs. 2 

 7n.andm'), 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. 



321. 2. GRAPTOLITHUS PRISTIS. 



Pl. LXXII. Figs. 1 a-s. 



Piioiiotus pristis. Hisinger, Leth. Suecica, 1S37, pag. Ill, pi. 33, sup. fig. 5. 

 Compare Graptolithus foHaceus, Murchison,' Sil. System, 1839, pi. 20, fig. 3. 



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

 with broad acute teeth." 



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

 distributed species of this genus wiiicii we have in the older slates. Tlie 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 inadvertently cited as authority for this species, on page 79 of tliis volume. 

 I Palaeontology.] 34 



