GRAPTOLITES OF xNEW YORK, PART 1 587 



Remarhs. This species was described by Hall as being associated at 

 Point Levis with Climacograptus antenna rius, etc., i. e. with 

 forms of the horizon of Diplograptus dentatus. 

 Hopkinson and Lapworth identified with Hall's species 

 a form obtained by them from the Lower Arenig of 

 Road Uchaf, Ramsey island, Wales. As they also 

 obtained Trigonograptus ensiformis at 

 the same locality it apparently occurs in Wales at 

 the same horizon as at Quebec and at the Deep kill, 

 but may, as indicated by the occurrence at the latter 

 place, appear already in the preceding horizon. 



Hall did not reach any definite conclusion as to 

 the generic position of the species ; Hopkinson and 

 Lapworth referred it with doubt to Dendrograptus, 

 stating that "in its mode of branching and in its gen- 

 eral aspect, it is a true Dendrograptus ; but its thecae 

 are quite unlike those of the typical forms of this genus, 

 being indicated only by minute indentations, as in the 

 genus Callograptus." They noticed however trans- 

 versal corrugations or joints which might represent 

 the thecae of Dendrograptus and therefore preferred /'g-.^o caiiograptus 



o -ST Jr cf. diffusus Hall. Ea- 



to place the species with Dendrograptus. In the the^thlc°a'i°lpertSres**' Deep 



writer's specimens, the apertures appear distinctly as 



appressed circular indentations, without traces of projecting thecae. 



PTILOGRAPTUS Hall. 1865 



Hall cited the following as the generic characters of this genus 

 [1865, p.l39] : "Frond plantlike, rooted ? single or branching. Branches and 

 branchlets plumose, the pinnules rising alternately on opposite sides of the 

 branches; celluliferous on one face only; branches cylindrical or flattened. 

 Substance corneous, dense ; apparently smooth exteriorly, or corrugated by 

 compression, or during fossilization." 



