GRAPTOUTKS OK NEW YORK, PART 2 



359 



is simply one and one half times the natural size. Admitting this (which 

 seems to me almost certain) I sec; no reason to question Emmons's identifi- 

 cation, or any necessity for doubting- his statement that "It is confined to 

 the Hoosic roofing slate." I have seen numerous examples of J), folia- 

 ceus Murchison (in forma secalinus Eaton) from those beds and 

 man)' of them agree very well with Emmons's description and figure. In 

 passing I may note that the remainder of Emmons's text tends to confuse 

 these views. 



That the species (cited above) found by Mr Walcott in the lower Cam- 

 brian (Georgia) shale of Parker's ledge could not be identical with the 

 species indicated either by Emmons's text or the one which (on the supposi- 

 tion that his figure is natural size) he figured, is shown (apart from other 

 considerations) by the extreme disproportion between the thecae in the same 

 spaee. Thus Mr Walcott's figure (stated to be "natural size") shows 36 to 

 40, Emmons's text states 24 and Emmons's figure shows 15 or 16 to the inch, 

 the last as I have shown above corresponding to the enlarged scale. 



a D. rugosus Emmons 



As already suggested by Professor Lapworth [Ann. & Mag. Nat. Hist. 

 1880, v. 5, p. 168-69] tn ^ s f° rm should I think be approxi- 

 mated to D. foliaceus Murchison. Pending an exami- 

 nation of material from Emmons's locality (Parrottsville, 

 Tenn.) it will perhaps be better to retain the name varie- 

 tally, although I strongly suspect it is rather a preservation 

 facies than a bona fide variety. 



b D. dissimilaris Emmons 



This form is only an obliquely compressed facies of 

 D. foliaceus Murchison. Among the specimens from 

 Magog (Upper Dicellograptus zone) I saw one which 

 completely paralleled Emmons's figure ; indeed the latter Fi g . 3 oi Di P iogra P - 

 might have been practically reproduced from it. ^ylKx^di^.™*' 



c D. obliquis Emmons. 1856 

 Am. Geol. v. 1, pt 2, p. 106, fig. 22 



" Straight, serrations turned obliquely outward, exposing the mouth of 

 the cell. 



The substance of the graptolite is olive-green ; thin and membranous. 

 There are 24 cells in an inch. The sides are similar ; axis, if any, con- 

 cealed. Found in Augusta county, Virginia." 



\. his species is another preservation facies of D , foliaceus Murchi- 



