(JUAITOLITES OF NEW VOUK, I'AltT 1 



713 



FiK.97 Ph yllograpt us ang'usti- 

 r o 1 i u s Hall. Middle portion of rhab- 

 dosome enlarged. Shows the shape of 

 the apertures in compressed state, and 

 the central canal. Deep kill. x4. 8 



D iplo gr :i p t u s d e n t ti t u s ) , specially in the lower part of the same, 

 exposed in the Ashhill (piarry at Mt Moreno, Iludson, Avhere it is very 

 common. llalFs types came from the shales of Point Levis; Ijiit, as no 

 associated forms are meutioued, the horizon is not determinable from his data. 

 Ami, however, cites it from several localities near Point Levis and Quebec in 

 association Avith species of the zones of T) i d y m ogr ap t u s bifid us 

 and of Tetragraptus. It can be thus inferred 

 that, in the Quebec region as well as at the Deep 

 kill, it ranges throuj^h several zones. A similar 

 range of the species has l)een observed by Elles 

 and Wood in (Jreat Britain. Also in Sweden 

 (Scania) it appears to be a form of the Tetra- 

 graptus horizon as well as of the Pliyllograptus 

 cf. typus zone. Broggei- found it associated with 

 P. typus and numerous varieties or mutations 

 of the two species, in the upper beds of the 



Phyilograptus shale of Christiania. Holm obtained his material from the 

 gray Orthoce'ras limestone of Oeland. 



Heinarlcs. While this species persists beyond the range of P. ilici- 

 f o 1 i u s into the horizon with D i p 1 o g r a p t u s d e n t a t u s , it begins 

 in the Tetragraptus l)eds, where P. ilicifolius is prevalent, with forms 

 that possess the long linear outline of P . a n g u s t i f o 1 i u s and the 

 uniform direction and curvature of the thecae in the middle portion, a 

 characteristic that seems to be dependent on the narrow development of 

 the rhabdosome, while in the antisicular part the ' thecae are still more 

 ascending than in P. an g u s t if o liu s , but not so strongly as in typical 

 P. ilicifolius. The apertural mucros are not yet as strongl}- developed 

 as in the P . a n g u s t i f o 1 i u s from the higher horizon, but of the same 

 character, viz extensions of the lo\ver margins. Indeed from a comparison 

 of the drawings of the apertural extensions of P. an gu s t if oliu s fur- 

 nished by Holm [text fig.94J with those of P . ilicifolius [text fig. 95], 

 it is to be inferred that they are of exactly the same character and differ 



