726 NEW YORK STATE MUSEUM 



end of the latter provided with two longer outei- aud two shorter inner 

 spines. 



Position and locality. Yery rare in the horizon with Diplograptus 

 dentatus at the Deep kill. 



Hemarhs. This species appears to be a vicarious form of the British 



G . f i m b 1 i a t u s of the same horizon, similarly as G . h y s t r i x 



^ resembles G. arraatus, another species of the British 



^^^^ Ellergill beds. Our type possesses a shape of the 



^■^^ rhabdosome, thecae and spines, much like G. fimbri- 



^■^ a t u s , but is larger, broader and has larger and less 



^^ closely arranged thecae. The spines are also, judging 



Fig.102 Giossograptus from the drawings of the British foim, stouter in our 



echinatus sp. nov. The- O ' 



cae. Deep kill. x6 • T j.1. 1 x i! xi • xi ^ 



species. In the character ot the spines the present 



species would seem to approach G. hincksii, from Avhich it differs 



however in the relative distance of these spines, which are more closely 



set in the Deep kill form (one to each theca, while in G. hincksii, 



according to Elles, probably only every second or third theca possessed 



spines). 



TRiGONOGRAPTus Nicholsou. 1869 



Nicholson proposed this genus [1869, p.231] for a form, which was 

 discovered by him in the upper Skiddaw slates and cited the following as 

 its principal characters: "Frond simple, diprionidian, rapidly tapering 

 toward the base and having perfectly plain lateral margins without denticles. 

 Cell partitions alternating with one another, and springing from an undulat- 

 ing or zigzag solid axis. A common canal is probably present, in which 

 case the axis must be excentric; but the evidence on this point is 

 incomplete." 



Of the features noted here, only the perfectly plain margins without 

 denticles remain as a distinguishing charactei' from the other Diplograptidae ; 

 for the frond is rapidly tapering only in the type species, T. lanceola- 

 tus, but not in the species here described, which has also been referred 

 by Nicholson to his new genus ; the cell partitions alternate in all Diplo 



