FAUNA OF THE TRENTON GROUP. 
9 
The inter-radial spaces are covered with small imbricating plates, 
and the anal opening is surrounded by a small pyramid of six 
triangular pieces. 
Just outside the tips of the rays is a ring of large thick plates 
ornamented with pits and rather large granules. Two or three of these 
plates are opposite each inter-radius, except the posterior one, which 
has four. They are much thicker and less scale-like than is usual 
in this group of fossils and such ornamentation is unique in the 
family. 
Chapman stated that his specimen was \ inch (12*7 mm.) in 
diameter. Specimen 1413 is 12 mm. in diameter, and another (5393) 
is only 10 mm. 
The plate structure as here described seems to be common to 
several species of Cameyella and Cytaster. 
Horizon and Locality . This species as now restricted is fairly 
common, but only at the type-locality. The original specimen was 
found at Peterborough, probably in the Cystid beds of the Prasopora 
zone in an old quarry near the entrance to Jackson park, where 
several specimens of Agelacrinitids have been collected. 
Cameyella youngi (Raymond). 
Plate HI, figure 4. 
Ottawa Naturalist, 1915, 24, p. 58, PI. 1, fig. 4. 
This species, named after G. A. Young of the Geological 
Survey, is very like C. billingsi , having straight rays, the same supra- 
oral structure, and about the same size. It differs in lacking the thick, 
ornamented plates of the outer ring, and the rays are broader. The 
inter-ambulacral areas are covered with large, transversely elongated, 
scale-like, imbricating plates, about fifteen to each of the lateral and 
anterior areas, whereas in the posterior inter-radius they are some- 
what smaller and more numerous. The anal opening is surrounded 
by two circles of small plates, five or six of which are in the inner 
circle. Outside the area to which the rays extend is a narrow 
margin of smaller imbricating plates. 
The liolotype (No. 3234, Victoria Museum) is from lot 12, eon. 
1, London, Ont., where it was collected from the upper part of the 
Prasopora zone of the Trenton by W, A. Johnston. 
Cameyella chapmani (Raymond). 
Plate II, figure 8; Plate III, figure 6. 
Ottawa Naturalist, 1915, 24, p. 58, PI. 1, fig. 3. 
This species differs from C. youngi in having longer and more 
slender rays, all of which show a slight curvature in the contra-solar 
10711—2 
