A NEW GENUS OF CAMBRIAN TRILOBITES. 
35 
Protolenus elegans, (W. D. Matthew, sp. m.s.s.) n. sp. 
Head-shield semicircular and more decidedly vaulted than 
in the succeeding species. 
Middle piece oblately subquadrate. Front Margin broadly 
arched, front area sloping down from the glabella and cheeks, 
and limited by a narrow, well 
defined marginal fold. Gla- 
bella prominent, about one 
quarter longer than wide, 
marked at the sides by three 
distinct furrows, directed 
backward. Occipital ring 
broadly rounded behind, sep- 
arated from the glabella by a 
distinct furrow. Fixed Cheek 
broad, subquadrate, bounded 
in front by a heavy ocular fil- 
let which is broadest at the 
inner end, where it rises from a depression in the shield on 
the line of the dorsal furrow. Ocular lobes prominent, long, 
moderately arched ; suture extending almost directly to the 
margin, both before and behind the eyelobe. Posterior Mar- 
gin bounded by a narrow fold somewhat geniculated one-third 
from the end, furrow broad, widening toward the end. 
Movable cheek with a narrow area, narrow marginal fold, 
and a long slender spine, arched inward behind, and nearly as 
long as the body of the cheek. 
Thorax of many segments, the joints having a prominent 
ring, grooved across at the anterior third ; pleura with a broad 
shallow groove, fading out one-third or one-half from the end 
of the pleura; the posterior bounding ridge of the pleura is gen- 
iculated about one-third from the end of the groove, and the 
pleura itself is continuous with the anterior bounding ridge 
and is prolonged into a slender spine. 
Pygidium unknown. 
Sculpture consists of minute shallow pits invisible to the 
unassisted eye. In one form of the species (perhaps a sexual 
variety) the slope of the head in front of the glabella and 
one joint of the thorax. All of the nat- 
ural size. 
