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. 11. 



{PlaieY^lW, Figs. 2, 3, 20.) 



Glabella anterior to the facial suture not known in the larger 

 specimen; the facial suture gives the anterior outline of 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 develcped, 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 



