CRUSTACEA. 
129 
Proetus Nevad^e, n. sp. 
PLATE XXIII, PIG. 19. 
Proetus marginalis, Walcott. Monogr. U. S. Geol. Surv., vol. viii: Pal. Eureka Dist., p. 210. 1884. 
The specimen identified by Mr. Walcott as Proetus marginalis, Conrad, in the 
work above cited, is a well-preserved and nearly entire individual, which ex¬ 
hibits points both of relationship and difference with the various representatives 
of the group of Proetus typified by P. Rowi, viz.: P. angustifrons, clarus, mar¬ 
ginalis (= Rowi) and Prouti. All these species are established upon differences 
which are of themselves slight but which nevertheless appear persistent. To 
any of these species, as here described, it becomes impossible to admit the 
Nevada form, as it differs from each member of this group in as many 
respects as those species differ from one another. It therefore seems neces¬ 
sary to regard it as having a distinct specific value founded upon characters 
which may be best expressed by a comparison with each of the species above 
mentioned. 
With P. angustifrons it agrees (a) in the character of the frontal border, which 
is convex near the marginal sulcus and slopes evenly to the edge, becoming 
faintly concave on the anterior limb ; (b) in the relatively narrow glabella, tan¬ 
gential upon the frontal border (in the type specimen the glabella has been 
slightly compressed laterally and thus appears somewhat narrower and more 
convex than is normal); (c) in the number of annulations upon the pygidium. 
It differs from this species in (a) the narrower and more elongate body; (b) the 
much smaller eyes; (c) the broader, more elevated and convex cheeks; (d) the 
longer and more slender genal spines; (e) the narrower and more elevated 
pygidial axis. 
With P. clarus it agrees in (a) the character of the frontal margin; (b) the 
length of the genal spines; (c) the form, contour and annulations of the pygi¬ 
dium. It differs from this species in (a) the much narrower and more regularly 
elliptical body; (b) the much narrower glabella; (c) the smaller eyes; (d) the 
narrower, more arched and more slowly tapering thoracic axis; (e) the narrower 
pygidial axis. 
