248 
form palpebral lobes, but our specimen is not sufficiently per- 
fect to complete the comparison. 
On the same piece of limestone is a small portion of ano- 
ther glabella, and on another hand specimen part of a fron- 
tal border of a cephalon. This lends encouragement to the 
belief that additional, and it is to be hoped more complete, 
examples will be forthcoming in the near future. 
BRACHIOPODA. 
Genus Obolella, Billings, 1861. 
(Geol. Vermont, 1861, ii., p. 946.) 
Obolella wirrialpensis, sj). nov. 
(Plate XXV., figs. 2 and 3.) 
.S';;. CVmr.— Valve ( 1 pedical) ovate to subquadrate, 
gently convex, rising dorsally into a small umbo : rounded 
ventrally and without emargination ; lateral angles rounded. 
Internal muscular scars hardly at all curved, diverging from 
one another, extending far forward, and tapering to a tine 
poin,t. Surface characters very marked and distinctive, con- 
sisting of a series of clean-cut, flat, concentric steps, the 
'"tread" of each step practically at right angles to its ''riser"; 
no concentric or radial striae of any kind. 
Ohs. — Obolella wirricd/pensis may be regarded a^ the char- 
acteristic fossil of the band of limestone lately discovered by 
Mr. Howchin, and adds another welcome genus to our Cam- 
brian list of fossils. It is a more quadrate form than most of 
the American Oholellce, with the exception of 0. cingulata, 
Billings :* in fact, the outline is more that of Oholus than 
Obolella. On the other hand, the internal structure, so far 
as it is preserved, is that of the latter, and the outline is more 
that of the British than the American species. It is further 
remarkable for its size, being equal to the largest of the 
latter, and far surpassing the former. Three selected speci- 
mens measure as follows : — - 
Dorsal to ventral. Transverse. 
a. 7 mm. 8 mm. 
b. 11 mm. 10 mm. 
c. 11 mm. 12 mm. 
The step-like nature of the concentric laminae is very char- 
acteristic, and cannot fail to arrest attention, even in frag- 
ments. 
* Billings— Pal. Foss. Canada, 1871, i.. p. 8, figs. 8-10. 
