GRAPTOLITES OF NEW YORK, PART 2 375 



qlossograptus Emmons 



The writer has touched the history of this interesting genus in 

 Memoir 7 in regard to species from the third Deepkill zone but since the 

 latter are so indifferently preserved that no structural details can be 

 ascertained, no contributions to the still very imperfect knowledge of its 

 structure, were made. A splendidly preserved series of specimens of the 

 genotype from the Normanskill shale at Glenmont near Albany and 

 another series of a closely related form from the shales at Summit, New 

 have furnished a few of the desired facts. 



Owing to the incomplete knowledge of its structure, the taxonomic 

 position of the genus is still uncertain. It is currently assigned to the Dip- 

 lograptidi, and has even been recently considered as a synonym of Diplo- 

 graptus by Freeh [1897, p. 624] who divides that genus into a nonspinose 

 and a spinose section. 



The above-mentioned material shows that in the genotype the section 

 of the rhabdosome was subrectangular, with each of the lateral faces raised 

 somewhat, either rooflike, or winglike, along the median line at the base of 

 the lateral row of spines, so that the section approached a hexagon (for 

 this seems the only way of explaining aspects like that represented in plate 

 27, figure 3, where in an oblique view the .row of lateral spines com- 

 pletely hides the apertural margins of the other side). There were two 

 different sets of spines, as Lapworth has demonstrated before, one of paired 

 apertural spines of the thecae and another of stronger and differently 

 directed spines or spurs along the median line of the lateral faces. The 

 latter were so arranged that only to every second theca corresponded one 

 pair [jtfgpl. 27, fig. 3 and text fig. 329, where the lateral spines of both sides 

 are shown]. As a result of these different sets of spines the two aspects, 

 the lateral and the ventral, are entirely different. In the former, only the 

 widely separated, upward directed lateral spines are visible, in the latter the 

 four times greater number of slightly reflexed apertural spines alone are 

 exposed [see pi. 27, fig. 1]. It can, therefore, not be wondered at that the 

 two aspects have been taken for different species to the present day, the 



