54 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE. [VOL. XI 
PELECYPODA 
MODIOMORPHA (?) ACUMINATA, Parks. 
Plate IV, Figures 12, 13 and 14. 
MODIOMORPHA ACUMINATA, Parks. Bur. Mines of Ont., 22nd Rep., pt. I, p. 194, 1913. 
This species is represented by nine specimens more or less com- 
plete. Some variation is shown in the general shape of the different 
examples, but this may be due partly to age; it is quite possible, how- 
ever, that more than one species is represented. 
The best preserved specimen is about 70 mm. long. The anterior 
end is very narrow and acuminate. The greatest height is well towards 
the posterior (about 35 mm.). The umbo is almost if not quite at the 
anterior end, and the hinge line is slightly arcuate. The surface is orna- 
mented by lines of growth only; these are more pronounced at intervals. 
There is a very slight depression in the sides of the valves giving a 
sinuate ventral margin. The left valve of this shell is shown in Figure 
12 and a cast of the right valve in Figure 13. This cast shows a.simple 
pallial line, a large anterior adductor scar and evidence of a fairly wide 
and heavy hinge plate. Unfortunately the posterior scar is not shown, 
nor is the detail of the hinge preserved. The figure, therefore, is not to 
be regarded as a restoration, but as showing only what is revealed 
in the specimen. A second cast shows some evidence of a large posterior 
scar in the dorsal region. This cast also shows evidence of the continu- 
ation of the hinge plate posteriorly and a peculiar wrinkling of the median 
portion of the shell which does not appear on the exterior. The speci- 
men figured as No. 14 is the interior of the left valve of a smaller shell 
which shows the hinge very well, but in which the tip of the beak is - 
broken off as well as the posterior margin. The edge of the actual 
specimen is shown in the figure with the probable correct outline dotted. 
The ventral part of the shell is filled with matrix and does not show the 
pallial line. Other examples present an anterior outline even more 
acuminate than the one figured, and these shells show scarcely any 
lateral depression. Despite the variations, I am inclined to include all 
the specimens in one species and to refer them to the genus Modio- 
morpha. This genus is Devonian, but its essential features are presented 
by one or other of our specimens; it has a heavier hinge plate than typical 
examples of Modiolopsis, it possesses a fairly strong tooth over the 
muscular scar in the left valve and, in the type specimen at least, pre- 
sents a slight depression in the lateral aspect with a consequent sinuosity 
of the ventral margin. It is freely admitted that more than one species 
may be represented, but the features revealed present common generic 
characteristics suggesting Modiomorpha; in view of this genus being 
