Case and 
Column of 
Drawers. 
TREMADOC GROUP. 

Reference to McCoyv’s 
Synopsis: and Figures of Genera. 
17 

Names and References; Observations, &c. 

case 
case 


Tsotelus. Pl. 1F, fig. 8, p. 169. 



Univalve Shells. 
Pteropods. 



TRILOBITA. 
Angelina Sedgwickii, Salter (Decade Geol. Surv. 
11. pl. 7). The most abundant of the Tre- 
madoe trilobites: allied to Olenus, but with 
15 body rings (Olenus has 14), and greatly 
larger than any known species of that genus. 
Even size is a character of some importance 
in classification. Occurs in all sorts of com- 
pressed shapes in the slate and sandstone. 
Dicellocephalus furca, Salter (Mem. Geol. Surv. 
Vol. m1. pl. 8, fig. 9, 10). Belongs to the 
section Centropleura (ib. p. 303). 
Asaphus (Isotelus?) affinis, McCoy. Perhaps 
distinct from the following species. The 
facial suture is marginal in front. 
Asaphus (Isot.?) Homfrayi, Salter (Mem. Geol. 
Sury. Vol. m1. p. 311, pl. 8, fig. 11—14). The 
earliest known form of this genus in Britain, 
if indeed the entire form of the labrum do 
not prove it a distinct genus nearer Ogygia. 
(See Lower Bala.) b, 344 is the labrum. 
The subgenus Jsotelus is uncertain here, for 
the labrum is not notched as in that form. 
Ogygia scutatrix, Salter (Mem. Geol. Surv. Vol. 
11. p. 312, pl. 8, f. 8, pl. 9, fig. 1). 8 or 9 
inches in diameter, and nearly round. More 
like the French species from Brittany, O. Des- 
marestt. 
Cheirurus Frederici, Salter (Mem. Geol. Surv. 
Vol. 111. p. 322, pl. 8, figs. 1—3). A species 
with a general resemblance to the C. (Ke- 
coptochile) Sedqwickii, McCoy (see Lower 
Bala), but with spines to the hinder rings 
of the body. 
PTEROPODA AND HETEROPODA. 
Theca simplex, Salter? (Mem. Geol. Surv. Vol. 
IIL. p. 352, pl. 118, fig. 22—26). This, if the 
same as the Arenig group species, is the 
only fossil common to both formations. In 
Canada there may be a transition from the 
Primordial Group to the Upper Cambrian, 
or at least to the Arenig Group: but not in 
Britain. 
Theca sulcata, n.s. Broad and short ; with lon- 
gitudinal folds. 
Numbers and Localities. 



a. 32, Garth and Penclo- 
gwyn, at Portmadoc ; Car- 
narvon. (Mr. Ash.) a, 24, 
Reduced in length by 
cleavage. b. 337—840, 
Various ages of this fine 
species. (Mr. Homfray.) 
a. 30 (Mr. Ash.) Moel-y- 
gest; in the bottom beds of 
the Upper Tremadoce. a. 
30*, Garth. (Mr. Homfray.) 
a. 26, Tremadoc, over Iron 
Works (Sedgwick). N.W. 
of Portmadoe. 
a. 25, Garth and Penclo- 
gwyn, Portmadoc. (Mr. 
Ash.) b. 342, 344, 358, 
figured specimens in Sal- 
ter’s Mon. Brit. Tril. pl. 24. 
(Mr, Homfray.) 
Penclogwyn, Portmadoc. 
(Mr. Ash.) 
Garth, Portmadoc. (Mr. 
Ash.) b. 345, 346, 347. 
Mr. Homfray’s specimen is 
figured in Mem. Geol. Surv. 
Vol. 11. p. 323, fig. 10. 
Garth, Tremadoc. 
Ash.) 
(Mr. 
b. 322, Llanerch, W. of 
Portmadoc, base of Upper 
Tremadoc. (Mr. Homfray.) 
3 
