ARENIG OR SKIDDAW GROUP. 
MippLe Camprian. f. ARENIG or SKIDDAW GROUP (Sedgwick). 
Base of Arenig and Arran Fowddy. The Stiper Stones Rocks, 
19 
4000—5000 feet thick. 
N.B. Some few of the Graptolites must 
be identified with those of true Lower Bala rocks, which overlie the Skiddaw Group proper in the Skiddaw 
district ; but all the rest are distinct. 
The graptolitic or upper portion of the Quebec Group of Canada is iden- 
tical with this: so are the graptolite gold-bearing shales of Victoria; and Prof. McCoy thinks several of the 
forms the same in each. I think the Victorian species are representatives only, but the genera are the same; 
while those of Canada are exactly ours in species and genera. 
The Angers slate is of this age. 
The whole 
group is unconformable upon the Tremadoc slate, and only one fossil is common to that formation. 



Names and References; Observations, &c. 
Numbers and Localities. 


Cake and Reference to McCoy’s 
Drawers. Synopsis: and Figures of Genera. 
Graptolites, 
Simple, double-celled, and 
twin-graptolites; dichotomous, 
and bushy forms. 

Gi G. sagittarius, p. 6. 
FL esses 
ED TEED 
Gi Synopsis, p. 7. 
Gi Synopsis, p. 8. 
Gi 




HYDROZOA or POLYZOA. Some natural- 
ists, as above said, have referred the Grap- 
tolites to Bryozoa or Polyzoa. More believe 
them Hydroid Zoophytes of the Sertula- 
rian type. 
Graptolithus Hisingeri, Carruthers (Geol. 
Mag. 1868, Vol. v.). G. sagittarius, Hisin- 
ger (Salter, Quart. Journ. Geol. Soc. Vol. 
vu. pl. 21, fig. 8). The Skiddaw specimens 
are only doubtfully referred to this very 
common Lower Bala species. 
Diplograpsus mucronatus, Hall (Pal. N. York, 
Vol. 1. pl. 73, fig. 1). These spinose species 
of Graptolites are now undergoing much 
revision, and it is probable great changes 
will be made in their names. D. barbatulus, 
Salter, is one of them, found at Ty Obry. 
Diplograpsus pristis, His. (Leth. Suec. pl. 35, 
fig. 5). A most common species, with only 
slightly prominent square-ended cells. 
Phyllograptus angustifolius, Hall (Grapt. 
Quebec Group pl. xvi. figs. 17—21). A re- 
markable leaf-like form, four rows of cells 
being placed crosswise on the stem or axis, 
instead of two, as in Diplograpsus. (Quart. 
Journ. Geol. Soc. Vol. xrx. p. 137, fig. 7). 
P. typus, Hall (1. c. pl. 15), is a larger species, 
but very like this. 
a. 33, Haykin Gill. a. 35, 
Knockmurton in Skiddaw 
slate. a. 34, Scaw Gill. 
a. 36, Craig ddu Allt, over 
Tremadoc Iron Works. 
a. 37, Ty Obry, east side 
of Tremadoc Estuary. (A. 
Sedgwick.) 
Tyddyn Dicwm, Tremadoc 
Estuary. (A. Sedgwick, 
1847.) 
a. 45, Skiddaw Slate. 
(From Bryce Wright.) 
