38 BULLETIN OF THE 
long has a process of the usual type, namely, a small mucronate tubercle or 
spine at the posterior extremity. The species occasionally attains a length of 
head of 20mm. The average size is within 10mm. Anterior to the glabella 
is a groove which separates the anterior border of the head from the glabella 
and the ocular ridges. Within the border is a broad, shallow groove. It is 
of medium size, rounded and curved. The distance between the extremities 
of the border, at the facial suture, is slightly less than the distance between 
the grooves defining the palpebral lobes. In line with the anterior margin 
of the glabella, or slightly behind the same and parallel with the anterior 
border, are the ocular ridges, increasing in prominence with the size of the 
individual, joining laterally the anterior end of the palpebral lobe. The 
groove which more or less distinctly defines the posterior margin of the ocular 
ridge joins the more distinct groove which separates the palpebral lobe from 
the fixed cheeks, The palpebral lobes are obliquely curved, having a postero- 
lateral direction. The facia] sutures anterior to the palpebral lobes bend 
slightly outwards to meet the anterior margin of the head. Posteriorly they 
curve towards the side and backwards, cutting the posterior edge within the 
postero-lateral angles. The cheeks are more convex in young specimens; in 
larger individuals they are only moderately curved. The extension of the 
occipital groove over the sides of the head is quite deep and distinct. Numer- 
ous specimens of free cheeks show that the postero-lateral extremities of the 
head were quite strongly spined. 
Three specimens have been found preserving most of the segments of the 
thorax, the posterior ones being more or less injured. One of these specimens 
shows thirteen segments, but there may have been fourteen or fifteen in the 
complete individual. The pygidium, judging from the specimens at hand, 
must have been relatively very small, perhaps about the size of that of 
Ptychoparia Piochensis. The pygidium has not been found. 
The side lobes of the thorax are moderately broader than the axial lobe. 
The middle lobe is strongly convex, and marked with a median row of mu- 
cronate tubercles, or small spines. These in the individual best preserving 
them were more prominent along the middle segments, being of moderate size 
anteriorly and practically obsolete in the last three or four segments. The 
species, as already noted, is quite variable; but the variations are none of them 
of any marked character, and all are abundantly connected by intermediate 
specimens. It takes the place of the series of species from the Vermont sec- 
tions known as Ptychoparia Adamsi, P. Teucer, P. Vulcanus, and the type of 
fossils in which the border is separated only by a short interval from the gla- 
bella, as figured by Walcott under P. Adamsi (Bulletin U. S. Geol. Survey, 
No. 30, Pl. XXVI. fig. 1c). These specimens would have been placed under 
P. trilineata, Emmons, had not such a good observer as Walcott decided, 
from a personal observation of the types, that the species was properly a 
Conocoryphe, which our specimens decidedly are not. 
Locality and position. — Stations Nos. 2 and 3, North hate Mass., 
Cambrian, 300 specimens. 
