OF CAPE BRETON AND NEWFOUNDLAND. 155 
II—SELENOPLEURA, Ang. 
1.—SELENOPLEURA COMMUNIS, Bill. 

Fic. 4.—Selenopleura communis, Bill—Centre piece of the head shield. Natural size. 
4 a. Same seen in profile. 4 b. Same seen in front. 
In “ Paleozoic Fossils” (Vol. IL. p. 72), Mr. Billings describes the above species, but 
without any figure. I reproduce his description here, with figures in illustration of the 
species, drawn from the type specimen in the museum of the Geological Survey at 
Ottawa :— 
“Glabella conical, convex, about two-thirds of the whole length of the head, about 
one-third wider at the neck furrow than at the front, on a side view considerably elevated 
above the fixed cheeks ; neck furrow well defined all across; neck segment thickened in 
the middle and bearing a small tubercle. The fixed cheeks are strongly convex, but not so 
prominent as the glabella. The dorsal furrows are deeply defined all around the glabella. 
The front margin has a strong rounded rim, separated from the front part of the cheeks 
by a narrow, but distinct groove; between the groove and the front of the glabella there 
is a gentle depression, which separates the anterior angles of the fixed cheeks. The eyes 
are small, situated a little in advance of the mid-length of the head, distant from the side 
of the glabella a little less than half the length of the head, and are connected with the 
front of the glabella by an obscure ocular fillet. Surface with a few scattered tubercles, 
just visible to the naked eye, and between these numerous minute tubercles, only seen 
when magnified. The glabella exhibits traces of two or three obscure furrows on each 
side. Length of the largest head collected, five lines. Occurs at Chapel Arm, Trinity 
Bay, Newfoundland.” 
On comparison of the above figure and description with that of Selenopleura Acadica, 
Whiteaves, it will be seen that the two forms are closely allied, and it is not improbable 
that the latter may be a variety of Billings’ species. The form of Selenoplewra Acadica 
figured in my former paper is the broad form, but in the narrow form the resemblance is 
closer. The broad form (as preserved in the shales of the St. John Basin of Cambrian 
rocks) is easily distinguished from Mr. Billings’ species by the complete separation of the 
anterior part of the fixed cheeks, and by the sharply upturned and narrow anterior 
marginal fold, and from both broad and narrow forms of the Acadian species, S. communis 
is distinguished by a difference in the granulation of the test. 
This species of Billings may be compared with Selenopleura brachymetopa, Ang., from 
which, however, it differs in the form of the glabella and in other respects; it comes 
nearer to the S. cristata of Linnarsson; it differs, however, in the eyes being nearer to the 
glabella, as well as in having a test which is granulated only (not tuberculated). 8. parva 
of the same author is also very near, but differs in the more sinuous anterior extension of 
the facial suture, the more gibbous cheeks, and the smoothness of the glabella; it is also 
a smaller species. 
