11 



bioadly-roimded sides, its diameter equal to onetliird of the sbort diam- 

 eter of the shell ; septa smooth, convexity nearly uniform, reaching 

 farther forward at the narrower sides than at the broader ones ; annu- 

 lations broadly rounded, passing sinuously around the shell, the sinuosity 

 being greater upon one of the broad sides than upon the other; inter- 

 spaces corresponding nearly in width and curvature with the annula- 

 tions. 



The shell-substance is not preserved upon the specimen, and the 

 surface-markings are unknown. 



Long diameter, eighteen millimeters ; short diameter, fifteen millime- 

 ters; distance from center to center of the anuulations, six millimeters. 



Position and locality. — Strata of the age of the Quebec group, Fisli 

 Spring, House range, Utah. 



CEUSTACEA. 

 Genus Leperditia IJouault. 



Leperditia BiYiA {sp. Hov.) — Shell not quite equivalve, inflated, the 

 greatest transverse diameter being about midlength and below the 

 middle ; obliquely subovate in outline, widest anteriorly ; the straight 

 hinge line about equal in length to tAvo-thirds of the entire length of 

 the shell, and ending, both i>osteriorly and anteriorly, in a small, dis- 

 tinctly projecting angle, which it forms with the anterior and posterior 

 borders respectively ; anterior margin obliquely rounded, with a mod- 

 erately broad, somewhat flattened border ; posterior margin abruptly 

 rountled, having a similar, but rather narrower, laterally - flattened 

 border, the flattening of the borders of both valves and at both ends 

 becoming obsolete upon reaching the ventral margin, which is broadly 

 rounded. Ventral border of the right valve bent sharply inward and 

 even a little upward, producing a narrow, plain, area like surface there, 

 which tapers to a sharp point at each extremity', and is nearly equal in 

 lengtli to the hinge-line. Ventral border of the left valve not bent 

 inward like that of the right, but the general convexity of the valve 

 extends to the edge; ni)on the ventral border of this valve, near its edge, 

 there are two distinct, comparatively large pores which open diverg- 

 ingly upon the surface, the distance between them being equal to a 

 little more than half the length of the hinge-line. 



Eye-tubercle not detected; surface apparently smooth. 



Position and locality. — Strata of the age of the Quebec group. Queen 

 Spring Hill, Schell Creek range, Nevada. 



Genus Megalaspis Angelin. 



Megalaspis belemnurus {sp. nov.) — Pygidium subtriangular in 

 outline, moderately convex transversely and only slightl3' convex lon- 

 gitudinally ; length, compared with the width across the anterior end, 

 about as fifteen to twenty-two; outer margins with a wide, smooth 

 border, slightly convex, except near the anterolateral angles, where 

 the convexity increases and the angles are abruptly rounded; anterior 

 margin moderately convex ; posterior extremity ending in a spine-like 

 process; segmentation indistinct, but most apparent upon the anterior 

 portion of the axis ; trilobation somewhat obscure ; axis depressed, 

 slightly higher than the adjacent portions of the lateral lobes, only 

 about half as wide anteriorly as one of the lateral lobes, continuous 

 posteriorly with the elevated caudal portion of the pygidium, which 



