227 



SPH^ROPHTHALMUS FLETCHERI. Plate xvii, figs. la-f. 

 Bull. Nat. Hist. Soc. of New Brunswick, voL iv, p. 280, pi. v, figs. 7 a-f. 

 General outline of the middle piece of the head shield, square, with a Sphseroph- 

 large, nearly cylindrical, glabella, which in front overhangs the narrow 

 marginal fold. The glabella has a width two-thirds of the length of the 

 glabella and occipital ring together. A strong furrow divides off the 

 third of the glabella. The occipital ring is narrower than this lobe of the 

 posterior glabella, and bears a tubercle at the middle. 



The fixed cheek is much drawn in behind and then arches downward 

 and outward to the posterior margin. The front of the cheek is tumid 

 and traversed by an ocular fillet directed diagonally backward. 



To the movable cheek is attached the large globular eye, placed near the 

 back of the cheek, the cheek is prolonged outward into a flat spine of 

 abnormal size ; this spine is as wide in the front quarter as the 

 cheek itself, and curves backward in a regular arch at first, but toward 

 the extremity becomes nearly straight. Of the two ribs which traverse 

 it, one is an extension of the posterior marginal fold, and the other is a 

 prolongation of the elevated middle part of the cheek. The flattened area Parts of this 

 on each side of the spine is a special expansion of the anterior and tr 

 posterior marginal folds, and towards the tip of the spine, narrows more 

 rapidly than the area occupied by the ribs ; of the flat areas, the outer 

 is hollowed on the upper side, and the inner one somewhat convex on 

 that side, especially toward the base of the spine. 



A young hypostome, imperfect at the front, which may belong to this 

 species, has a narrow, elevated obconical anterior lobe extending two- 

 thirds of its length ; and an encircling, more depressed posterior lobe, 

 occupying the rest of the hypostome ; both lobes are convex, and no border 

 fold is visible. 



The pygidium of this species is broadly triangular, and has a strong 

 obconical rachis of three segments, the third nearly as long as the two 

 anterior. These latter have each an obscure lobe at each side. The side 

 lobes are narrow triangles, with a tubercle at each anterior outer 

 corner. There is a distinct but narrow border fold at the sides and 

 posterior end of the pygidium. 



Sculpture. This is exceedingly minute and appears to consist of very 

 fine granulations with a smooth, shining surface on the front lobe of the 

 glabella; this part of the glabella shows occasional scattered small 

 tubercles. 



15 c. R. 



