ADmTlONAL NOTES ON THE CAMBIUAN OE CAPE UUETON 
393 
The dorsal valve is orbicular in outline ; its height is less than 
half of that of the ventral. The valve is strongly arched in the 
posterior half, but somewhat flattened on the posterior lateral 
slopes. Interior . — This is marked by three strong radiating ridges in 
the posterior half of the valve ; at the origin of these ridges are a pair 
of pits with a small tubercle in each, marking the position of the 
cardinal muscles. Of the three radiating ridges, the central is a nar- 
row median ridge, with three sharp keels ) for half of the length of 
the valve this ridge is prominent, but fades away in the anterior third 
of the valve; at the end of this ridge would be the scars of the 
anterior laterals (“j-”) The lateral ridges are broader than the 
mesian one, but not so long ; outside of them are the impressions of 
the lateral muscles. 
Sculpture . — The roughness of the matrix prevent a good presenta- 
tion of the surface characters of this species. Some examples of the 
ventral valve show fine concentric ridges, of which there are about 
ten in half the length of the anterior slope {i. e. about 10 to 1 mm.) . 
the surface of these ridges appears to be granular. 
Size . — The largest dorsal observed was 3 mm. across, but the 
greater number are not more than 2 mm. The full-grown ventral is 
about 2 mm. high, and the dorsal less than one. 
Horizon and locality . — In gray flags of Div. 2c on the eastern 
slope of the valley of McNeil Brook, on the road to Trout Brook. 
Found in various attitudes in the sandy bed. The ventrals are both 
upright, inclined and lying on their sides in the layers. From this 
locality Mr. Fletcher has reported Obolella, a genus in which, at the 
time his report was written, many of these small brachiopods were 
included. 
liinnarsson described very fully a species like this from the Para- 
doxides beds of Sweden.* He found it to range through the whole of 
the Paradoxides Zone. Our form belongs somewhat higher up. 
From A. Bailey i of the (lower) Paradoxides beds in New Bruns- 
wick! this species is distinguished by its smaller size, narrow umbonal 
ridge to the ventral valve, higher cardinal area, and by the enclosing 
longitudinal pits that enclose the umbonal ridge. It diflfers from A. 
* Loc. cit. 
t Trans. Roy, Soc. Can., Vol' iii, sec. iv, p. 36, pi. v, figs. 13, 13a, h and 
