8 



the center and outer margin of the head, which distance is also about 

 equal to the length of the eye. Glabella distiuctlj^ lobed, the furrows 

 extending nearly or quite to its center ; frontal lobe prominent, tumid, 

 regularly rounded in front, and a little wider than the remainder of the 

 glabella. 



The remainder of the body is unknown except a single specimen of 

 the long third pleura of the right side and another short one. Both of 

 these are grooved and marked as is usual in the genus. 



This species is nearly allied to 0. Vermontana, the type specimens of 

 which are from strata of the Potsdam epoch in the town of Georgia, Vt. 



Position and locality. — Eocks of the Potsdam epoch at Pioche, Ne- 

 vada. 



Olenellus Howelli Meek (manuscript). — Head semi-oval in out- 

 line, strongly convex, the length on the median line being to the great- 

 est breadth about as three to five ; exterior margin having a strong 

 raised border of nearly uniform width all around, and which is also con- 

 tinuous with the moderately strong spines of the posterolateral angle 

 of the head ; length of the spines equal to about one-half the length of 

 the head on the median line; posterior margin also with a raised bor- 

 der, extending on each side from the occipital segment to the base of the 

 spines ; width of this border not uniform like that of the exterior mar- 

 gin, but is widest a little beyond the midlength of each side, and 

 narrowest near the base of each spine, where it again suddenly widens 

 outward, blending with both the spine and the lateral border. This 

 widening of the border there rounds the angle between the posterior 

 margin and the spine, and also rounds the posterolateral angle of that 

 portion of the cheek which is inclosed within the raised borders. A 

 shallow, linear depression runs around the head, just within the raised 

 border, giving the broad cheek-surfaces the appearance of being slightly 

 inflated. Eyes large, very prominent, extending from opposite the 

 anterior furrow of the glabella to nearly opposite the middle of the 

 occipital lobe; the palpebral lobe of each eye blending with the outer 

 ends of the anterior, middle, and posterior lobes of the glabella. 



Glabella large, very prominent, distinctly lobed ; the furrows, espec- 

 ially the occipital one, not extending quite to the center on either side; 

 the occipital and posterior lobes of about equal size ; the middle and ante- 

 rier ones about equaling each other in size, a little smaller than the two 

 first named ; frontal lobe large, tumid, extending forward to the shallow, 

 linear depression just within the raised border of the head, regularly 

 rounded in front, a little wider than the remainder of the glabella, 

 bordered on each side by a shallow, linear depression, which ends ante- 

 riorly in the marginal depression just named. 



Surface apparently smooth. Pemaiuder of the body unknown. 



This species is related to 0. Thompsoni from strata of the Potsdam 

 epoch in the town of Georgia, Vermont. 



As the genus Olenellus is held by geologists to mark a distinct and 

 characteristic horizon in American strata, its discovery in that distant 

 locality is peculiarly interesting. It is also an interesting and signifi- 

 cant fact that the two si)ecies here described respectively represent in 

 their specific characters the two originally-described species of the genus 

 found associated in the primordial rocks of Vermont and Canada, as 

 these are found associated in rocks of the same period in Nevada. 



The specimens from which the descriptions of the two species of 

 Olenellus herein recorded were made are the same that were used by 

 Mr. Meek in his original descriptions and naming of the species. 



Fosition and locality. — Pocks of the Potsdam epoch, Pioche, Nevada. 



