GRAPTOLITES OF NEW YORK, PART 2 253 



observed in others. Its citation from the Utica shale of the Mohawk valley 

 is probably erroneous [see p. 35). Gurley has also recognized it in the 

 shales of the novaculite area in Arkansas and Elles and Wood record it 

 (probably in a variety) from the Glenkiln shales of S. Scotland and N. 

 I reland. 



Remarks. D . serratulus is well characterized by its large sicula, 

 its straight branches, and narrow, but rather rapidly widening branches (a 

 feature not well brought out in the original drawing of the species). A 

 varietal form is represented by a single specimen from the shales at Ken- 

 wood [fig. 156]. In this the thecae retain their nepiastic character for a 

 longer time and in consequence of this the branches remain as narrow as in 

 the sicular region of the typical form, lack the rigidity of those of the 

 typical serratulus and form a larger angle of inclination (150 ) while 

 the sicula possesses the characteristic long form of the species. This 

 variety may be distinguished as D . serratulus var. j u v e n a 1 i s. We 

 are also certain that the form referred by Elles and Wood to D. serra- 

 tulus is at least varietally distinct, for it possesses a smaller angle of 

 inclination, uniform width of branches and more loosely arranged thecae 

 (7 to 8 as against 9 to 10 in the typical material). 



Didymograptus subtenuis (Hall) 



Plate 14, figures i, 2 



Graptolithus tenuis (Portlock) Hall. Pal. N. Y. 1847. 1: 272; pi. 74, fig. 2a-d 

 G r apt oli thus subtenuis Hall. In Miller's Am. Pal. Foss. Ed. 1. 1877. p. 244 

 Graptolithus subtenuis Walcott. Alb. Inst. Trans, v. 10. 1883. (Advance sheet. 



l8 79- P-35) 



Dicellograptus tenuis Lapworth. Rov. Soc. Can. Trans, v. 5, sec. 4. 1886. p. 178 

 Leptograptus tenuis Lapworth. Ibid. p. 1 83 



Leptograptus subtenuis Walcott. Geol. Soc. Am. Bui. 1890. 1:338 

 Leptograpsus subtenuis Gurley. Jour. Geol. 1896. 4:296 

 Didymograptus tenuis Ruedemann. N. Y. State Mus. Bui. 42. 1901. p. 54of 



Description. Rhabdosome consisting of two very thin (initial width 



.2 mm) and very slowly widening, slightly flexed, nearly straight branches, 



which attain great length (fragments of branches 20+ cm long quite 



