GRAPTOLITES OF NEW YORK, PART 2 



3 



Certain slabs of the collection from the Normanskill shale at Glenmont 

 near Albany contain nothing" but a smaller variety of this form [see pi. 25, 

 fig. 1 I ; the rhabdosomes while possessing all the true characters of this 

 variety, are uniformly smaller, hardly more than 20 mm long and 2 mm 

 wide. This type approaches in length closely to I ) . a n g u s t i - 

 folius, a form of similar thecal shape but always remains 

 notably broader. 



c Diplograptus foliaceus var. trifidus Gurley 

 Cf . D i p 1 o g r a p t u s foliaceus var. calcaratus Lapworth. 



Cat. "West. Scott. Foss. 1876. p. 6; pi. 1, fig. 30 

 Diplograptus trifidus Gurley. Geol. Sur. Ark. Rep't. 1890. 



3:417; pi. 9. fig. 3, 4 

 Diplograptus trifidus Gurley. Jour. Geol. 1896. 4:298, 307 



Dr Gurley has described in the Annual Report of the 

 Geological Survey of Arkansas a large Diplograptus which 

 occurs in that state in chocolate-brown limestone in association 

 with the Dicellograptus fauna and which is a striking form in 

 several regards. It is of large size, attaining 60 mm in length 

 and 6 mm in width and possesses a very broad nemacaulus 

 (2 mm) suggesting the inflated one of D. vesiculosus. 

 It is most conspicuous, however, by the three power- 

 ful spines of its sicular end, a long daggerlike 

 virgella and two strong, curved lateral spurs. Its 

 thecae number 8 to 10 in the space of 10 mm and 

 are those of a foliaceus. 



Gurley was at the time of drawing up his descrip- 

 tion not aware of the fact that Lapworth had already 

 proposed the variety calcaratus of D. foli- 

 aceus for a form with just such strong terminal spurs. Later [1896, 

 p. 307] he has stated that though "the identity of the two forms can hardly 

 be asserted at present as Lapworth's calcaratus rests solely upon the 

 figure of a basal fragment," he would not have described D. trifidus 



\ 



f 



Fig. 294, 295 Diplograptus 

 foliaceus var. trifidus 

 Gurley. Copies of Gurley's 

 original figures 



