A Nczv Lower Cambrian Fauna. — Burr. 47 
the heads are considerably larger. The largest head found 
has a length of 15 m m. and a maximum width, without the 
free cheeks, of 20.5 m m. The glabella is 12.5 m m, long and 
9 m m. in its greatest breadth. 
Microdiscus. cf. M. Helena Walcon. 
Microdiscus Helena Walcott, 1889. U. S. Natl. Mus. Proc, vol. 12, 
p. 40. 
A single pygidium of Microdiscus has been found. It 
stands. in relief on the surface of a fragment which has been 
exposed to the weather. The details of its structure have be- 
come obscured, but the general outlines are quite distinct. 
It is the pygidium of a small individual, being but 2+ m m. 
in breadth and a trifle less in length. . It appears to show not 
more than five segments. It is strongly convex. It resem- 
bles M. helena rather closely, but is not perfect enough for 
positive identification. 
Leperditia cf. L. solitaria Barrarvde. 
Leperditia solitaria Barrande. Syst. Sil. de la Boheme, vol. r,suppl. 
:pi. 23. 
Five individuals have been found which apjicar to be os- 
tracods of the Leperditia type. The smallest of these is 8.5 
m m. long, and 5 m m. in hight. Its hinge line is nearly 
straight, and curves abruptly at the ends. The valve is only 
moderately convex. The two ends are apparently symmetri- 
cal. Three of the other individuals resemble this one in size' 
and shape. The fourth is considerably larger, having a length 
of 1 1.5 m m. It differs from the others in form, also. The 
hinge line is less straight and the valves more convex. It 
shows distinct lines of growth. It bears a ridge comparable 
to the umbonal ridge of a lamellibranch. This specimen is 
only provisionally referred to Leperditia. 
Obolella atlantica Walcott. 
Obolella atlantica Walcott, 1889. U. S. Xatl. Mus. Proc, vol. 12, 
p. 36. 
Nine individuals are referred to this species. In no case 
is the preservation suf^ciently good to bring out clearly the 
details of structure and ornamentation. In all, however, the 
lines of growth are traceable, while two specimens show 
faintly the radiating striae. The largest specimen has a length 
