554 bulletin: museum of comparative zoology. 



specimens are the property of the Geological Survey of Canada, and 

 were collected by Dr. August F. Foerste. 



An allied form is found at the same horizon at Kirkfield, Ontario. 

 The two pairs of anterior glabellar furrows in this form are fainter, 

 and the basal lobes of the glabella are more sharply isolated than in 

 the specimens from Goat Island. 



Ceraurinus scofieldi (Clarke). 

 Plate, fig. 4. 



Cyrtometopus scofieldi Clarke, Pal. Minn., 1897, 3, pt. 2, p. 735. 



The type of Cyrtometopus scofieldi Clarke shows only the cranidium. 

 The specimen figured (Plate, fig. 4), presents, in addition, a free 

 cheek, two thoracic segments, and a fragmentary pygidium. The 

 free cheek is relatively large, is roughly triangular, and is only slightly 

 convex. It has a relatively broad border, separated from the main 

 portion of the cheek by a narrow lateral furrow. The axial portion of 

 the thorax is, in width, slightly less than one third the total width. 

 The pleura are divided into an inner and an outer portion by a faint 

 constriction. The inner portion is cut by a diagonal furrow. 



The diagonal pleural furrows, the parallel sides of the glabella, and 

 the form and course of the pair of posterior glabellar furrows prevent 

 the identification of this species as Cyrtometopus. These features, the 

 furrow on the upper surface of the palpebral lobe, and the course of the 

 neck-furrow, are the characteristics of Ceraurinus. 



The specimen is apparently enrolled and the spines of the pygidium 

 seem to project from beneath the front of the cephalon. There is one 

 pair of relatively large spines enclosing a small notched plate. The 

 pygidium is smaller than in the other species of the genus. 



Ceraurinus scofieldi is apparently most closely allied to Ceraurinus 

 marginatus, C. icarus, and C. pompilius. These four species are all 

 characterized by the flatly cylindrical glabella with rounded front, and 

 by posterior glabellar furrows of about the same pattern. The first 

 three also agree in having the middle pair of glabellar furrows about at 

 right angles to the axis of the glabella, and the anterior pair at a very 

 slight angle, eyes similarly placed, palpebral lobes with a furrow on the 

 upper surface, and a broad cephalic border. Ceraurinus scofieldi 

 may be distinguished from Ceraurinus marginatus most readily by the 

 greater inclination backward of the posterior pair of glabellar furrows 

 of the former, the position of the eyes further back, and by a narrower 



