ORAP'roi.rn;;^ oi' new yoiik. p.mit i 715 



Position and localities. In the last layers; of graptolite bed 2 (Tetra- 

 graptus horizon), and throughout the horizon Avith T) i dy m ograp t u s 

 b i f i d u s . Also in the next horizon with D i p 1 o g r a p t u s d e n t a t u s 

 as well at the Deep kill, as at Mt Moreno. In Canada this form has been 

 found, according to Hall and Lapworth, onl}- in the 

 St Anne beds, representing there the horizon with 

 D i d y ni o g r a p t u s b i f i d u s . Ami records it also 

 from an outcrop near the city hall of Levis, in association 

 with Didy m ograp tus bifidus, etc. and from a 



1 T 1 /-,! TV • /-(I 1 ^ -1 ^ Fiff. 98 P hyl 1 ograp tus 



locality on the Chaudiei'e river, (xurley observed it also anna Haii Mar-inai por- 



J J tioa ol rhabdosome, to show 



• , n xTj. X' xi T>1 i. T J i? the appearance of the thecal 



in suites ot graptolites troin the l^eekmantown beds or apertures in the compressed 



_ condition. Deep kill. x4.5 



Arkansas and Nevada. It is known from the Middle 



Skiddaw slates of the Lake district of England, where it is found associated 



with P. an g u s ti f o 1 1 u s; and from south Scotland. 



Remarhs. This form is easily recognized, as pointed out by Hall and 



Elles, by its small size and the great number of thecae in a given unit of 



length. This is greater than in any other species and goes, in the Deep 



kill specimens, beyond the number obtained by the above cited authors. 



The greater width of the end is also, though not an unfailing, }^et a strik- 

 ing character of the majority of the specimens, and the 

 acute slender form of the mucros serves also to distin- 

 guish this species from the associated forms; specially 

 from dwarfed specimens of P. ilicifolius, which 

 have been noticed in the material. 



The specimens observed in the last horizon of the 

 Fig. 99 phyiiograptus Dccp kill sectiou have a still more condensed aspect, 



anna Hall. Ashjull quarry 



at Mt Moreno, xo their thccac number as much as 22 in the space of 



10 mm, and the total size attained is not more than 3.6 mm. They represent 

 clearly a last dwarfed and paracmic mutation of the species, which might be 

 designated as P. anna mnt. ultimus [pl.l5, fig.29, 80]. 



In the beds with D i p 1 o g r a p t u s d e n t a t u s exposed at Mt Moreno 

 a form of P. anna is extremely common, \vhich, while, by its outline, 



