434 MR. E. R. COWPER REED ON THE [Aug. 1 896, 



cheeks the neck-segment diminishes to about one-half the breadth, 

 and height of the neck-lobe. The fixed cheeks are produced as 

 regularly swollen ' anterior wings,' on each side of the glabella, and 

 these wings are about as wide as the glabella. In front of the 

 glabella they unite and constitute the convex frontal area, which is 

 as high as the ' anterior wings ' but wider, and has, like them, a 

 steep inner or posterior, but gentler anterior or outer slope. 



The facial sutures cut the front margin of the head-shield at a 

 distance one from another equal to about 1| times the basal width 

 of the glabella. Each runs at first backward and slightly inward 

 to the antero-lateral groove, which separates the frontal area from 

 the anterior wing of the fixed cheek; then it takes a slight outward 

 trend to the eye-lobe, which is very indistinct in our specimens ; 

 from this point it makes a sudden bend outward so as to become 

 nearly parallel to the hind border of the head-shield, finally bending 

 sharply backward to cut the margin. 



What appears to be the free cheek (badly preserved) is triangular 

 in shape and not swollen ; it bears a large, smooth, ovate eye, which 

 lies a little behind the middle of the glabella and at the sharp 

 re-entrant angle of the facial suture. The genal angle appears to 

 have been produced into a spine. 



The front and sides of the head-shield are surrounded by a narrow, 

 smooth, raised, rounded border, separated from the frontal area and 

 free cheeks by a marginal furrow, which is nearly as wide as the 

 axal furrows. 



The whole surface of the head-shield is covered with fine granu- 

 lations and scattered tubercles of various sizes without any definite 

 arrangement, but the middle point of the neck-lobe of the glabella 

 is generally marked by a specially large isolated tubercle. 



The thorax and pygidium are unknown. 



Affinities. — The close resemblance to Tornquist's Trilohites trira- 

 diatus l which our Keisley form bears led Messrs. Marr and Nicholson 2 

 to compare it with that species ; but on a minute examination of 

 our specimens by the side of Tornquist's figure and description, I 

 am convinced that they must be considered distinct. The shorter 

 length, more rounded and ovoid outline, and greater width of the 

 glabella ; the absence of the pair of notches or short furrows at its 

 base ; the n on- continuation of the median notch as a groove over the 

 frontal area ; and the more rounded and swollen character of the 

 anterior wing of the fixed cheek, are the chief reasons which lead me 

 to this conclusion. 



Tornquist's species and ours are, however, very closely allied, and 

 present in common important features, which mark them off from 

 a typical Gypliaspis, namely, (1) the absence of the basal lobes to the 

 glabella ; (2) the presence of the three radiating notches or grooves 

 at the front end of the glabella. 



1 Tornquist, ' Undersokn. ofv. Siljans. Trilob.' Sver. geol. Undersokn. pi. iii. 

 fig. 18, p. 92. 



2 Marr & Nicholson, 'The Cross Fell Inlier,' Quart. Journ. Geol. Soc. 

 vol. xhii. (1891) p. 507. 



