44 
K. L. Prexdergast. 
Description . — The small size of this species is shown by the table of 
dimensions : — 
— 
Maximum 
width. 
Length 
hinge-line. 
Height. 
Synlypes : 
1. Conjoined valves 
8*0 
4-6 
6-5 
2. Pedicle valve 
8*5 
5* 7 
7-0 
3. Brachial valve .... 
6-7 
5-0 
5*4 
4. Conjoined valves 
9-0 
0-2 
8-0 
Irwin River Specimeyis : 
1. Fossil Ridge 
10-8 
6-8 
8-5^ 
7*1 ^ 
4-2 
7-1 J 
Brachial 
2. Fossil Cliff 
10-4 4 
5-0 
9-4 j 
Valves 
8-9 + 
5-3 
8-4 
15-9 
11-0 
15-4 
Pedicle 
\"alve 
The i)ediele valve is small, thin-shelled and moderately inflated; it 
diminishes in convexity gradually towards the lateral and anterior margins, 
somewhat suddenly towards the cardinal margin. The area is small, narrow 
and triangular, its lengtli less than that of the hinge-line. The shell sub- 
stance is lamellar and has a silky texture, the laminae interrupted by the 
spines, which closely adhere to the surface of the shell. A few erect spines 
are present on the ears. The muscle scars are situated high up in the valve 
and have a deltoid outline, the delta divided medially l)y a groove into the 
two triangular areas. They are non-dendritic. 
Cardinal Process of Stroplialosia etlieridgei in sp. (XH). 
The brachial valve is flat in the visceral region with geniculated margin 
and has a silky laminated and imbricated surface. The hinge-line is short 
and the cardinal angles are obtusely rounded. The area is distinct, triangular 
with the umbonal angle flattened; the pseudo-chilidium is triangular and 
wide with two deep, narrow sockets, inclined to the median septum at its 
base. The cardinal process is narrow near the hinge-line, but swells out to a 
