HYDE: CAMAROPHORELLA. 39 
variation in external characters. Following is a series of measure- 
ments in millimeters made from the molds. 
No. 
Height. 
Breadth. 
Thick- 
ness. 
No. 
Height. 
Breadth. 
Thick- 
ness. 
1. 
9.0 
9.9 
5.5 
15. 
19.0 
18.7 
10.0 
2. 
11.7 
13.0 
6.0 
16. 
19.3 
21.4 
11.0 
3. 
13.5 
14.4 
6.2 
17. 
20.4 
22.4 
13.2 
4. 
13.7 
15.0 
7.6 
18. 
21.0 
22.4 
11.6 
5. 
14.5 
15.0 
7.8 
19. 
21.6 
26.0 
15.8 
6. 
14.8 
16.8 
8.0 
20. 
22.0 
25.0 
12.7 
7. 
15.9 
15.7 
7.8 
21. 
22.1 
25.0 
14.3 
8. 
16.3 
20.1 
9.2 
22. 
22.3 
24.5 
14.6 
9. 
16.4 
15.1 
8.8 
23. 
22.6 
23.6 
15.8 
10. 
17.5 
19.8 
24. 
22.8 
25.3 
11. 
17.7 
20.4 
25. 
23.0 
28.7 
15.7 
12. 
18.2 
20.0 
11.2 
26. 
24.3 
26.8 
15.0 
13. 
18.2 
21.5 
9.6 
27. 
24.5 
28.0 
15.5 
14. 
18.3 
20.0 
9.1 
The surface of the shell is somewhat irregularly marked by fine 
concentric striae and occasional slight wrinkles of growth. These are 
crossed by very fine but distinct radiating striae, eight or ten of which 
occupy the space of one millimeter. These striae are sharply rounded 
and the flat furrows between are considerably broader. 
The beak of the pedicle valve is only moderately incurved, not con- 
cealing the delthyrium which is entirely closed by the deltidial plates. 
The pedicle opening is subterminal and in the adult stages is carried 
into the shell substance considerably beyond the original limits of the 
delthyrium. The deltidial plates and pedicle opening are not com- 
monly seen owing to the nature of the material. In one specimen 
showing the interior of the shell (pi. 9, fig. 44) the inner surfaces of 
the deltidial plates are shown between the tip of the cardinal plate 
and the pedicle opening. 
Pedicle valve. — A spondylium is present in the pedicle valve formed 
by the coalescence ventrally of the dental lamellae. It is strongly 
concave toward the interior of the shell and is supported throughout 
its entire length by a low median septum, except occasionally in the 
tip of the beak where it may rest for a very short distance on the valve. 
The median septum extends for one third of its length beyond the 
anterior end of the spondylium, and its total length is less than half 
that of the valve. It does not penetrate into the cavity of the spondy- 
lium, but a faint ridge only is discernible on the floor of the platform. 
