124 
BULLETIN OF THE LABORATORIES 
erably smaller on the glabella, and far more numerous ; there is a 
greater distance between the eyes and the continuation of the occipi- 
tal furrow, and this is occupied by a greater number of rows of tuber- 
cles, three. This is evidently the most closely related species, but if 
his drawing is at all correct then our species is quite distinct. 
Encrinurus Mitchelli, sp. n. 
XIII, Figs. 2, 3, 20.) 
Glabella anterior to the facial suture not known in the larger 
specimen; the facial suture gives the anterior outline 6 f the remainder 
of the glabella an evenly rounded appearance. The sides of the 
glabella are moderately concave, widening anteriorly, having the 
greatest breadth at two-sevenths its length from the occipital furrow. 
On either side along the dorsal furrow are a row of large and very 
conspicuous tubercles or lobes which form a marked contrast with the 
rather small tubercles on the remainder of its surface. In the speci- 
mens before us there are five of these ; the fiist is compressed antero- 
posteriorly, the next three are well develeped, and the fifth is con- 
siderably smaller than these. The remainder of the glabella is rather 
thickly set with small tubercles. The fixed cheeks also have more 
conspicuous tubercles along the dorsal furrow, of about half the size 
of the corresponding tubercles on the glabella, and alternating with 
them, the eyes are about equally distant from the dorsal furrow and 
the continuation of the occipital furrow. Posterior to the eyes the 
facial sutures form a very sharp angle with the occipital furrow cut- 
ting the lateral margins of the head just at furrow; at first two rows 
of small tubercles separate them, quickly merging into one. The 
tubercles increase in size toward the dorsal furrow. A moveable 
cheek belonging to the more broken specimen shows that the deep 
dorsal furrow after sharply defining the anterior part of the fixed 
cheeks, makes an equally prominent depression as it enters the move- 
able cheek, quickly decreasing in depth and broadening as it turns 
backward along the margin of the head. The part anterior to this 
groove according to the general morphology of the genus Encrinurus 
once must have formed the anterior part of the glabella. Like the ad- 
jacent parts of the glabella, it is covered with small tubercles. The 
