THE NATURAL HISTORY SURVEY. 267 



opposite the posterior lateral glabellar furrows where they 

 bend much more abruptly downward to the frontal margin and 

 continue across the front as a marginal furrow. The glabella 

 smooth, sub-globular, comprising nearly the entire head, strongly 

 protuberant anteriorly beyond the frontal margin; the two 

 anterior pairs of lateral furrows and lobes often entirely ob- 

 solete, although the furrows are sometimes represented by 

 slight undulations at the sides of the glabella; posterior furrows 

 strong and deep, describing nearly a half circle and extending 

 from the dorsal furrows in front to the occipital furrows behind, 

 isolating the posterior, lateral lobes which appear as two nearly 

 circular nodes at the base of the glabella; occipital furrow 

 deep and rather broad in its meglian portion, becoming narrower 

 t back of the posterior glabellar lobes, the occipital segment 

 narrower, its surface elevated nearly as high as the surface of 

 the glabella in front of the occipital furrow. Cheeks reduced in 

 size, sub- triangular in form; anterior limbs of facial sutures 

 extending upward from the anterior margin parallel with and 

 close to the outer margin of the dorsal furrows to the eyes, 

 the posterior limbs directed at nearly right angles to the an- 

 terior limbs and cutting what appears to be the posterior margin 

 of the head; eyes small, situated opposite the outer extremities 

 of the posterior lateral glabellar furrows; fixed cheeks in front 

 of the eyes occupied entirely by the dorsal furrows, back of the 

 eyes they are broader, sub-triangular in outline with a deep 

 post-marginal cheek furrow extending from the lateral ter- 

 minations of the occipital furrow; free cheeks sub-quadrangular 

 in form, flattened in their outer half, elevated within to the 

 margin of the eyes, they are produced posteriorly to such an' 

 extent that the posterior limbs of the facial sutures seem to cut 

 the posterior margin of the head as in the order Opisthoparia. 



Thorax with ten segments, strongly trilobed, the axis oc- 

 cupying more than one- third the total width, the inner half of 

 the pleural lobes flattened, the outer half bent abruptly down- 

 ward to the lateral margins. 



Pygidium small, sub-semicircular in outline; the axis 

 broad and strongly convex with three segments and a terminal 

 flattened region; the pleural lobes much reduced in size, divided 

 into three segments all of which are produced distally as free 

 points. 



The dimensions of a small but nearly perfect cephalon are: 

 maximum width 14 mm., maximum length 10 mm., height 

 from frontal margin to occipital segment 1 1 mm. 



