262 PALEONTOLOGY. 



OEUSTACEA. 



' Genus PROETUS Stein. 

 7 >o Proetus peeoccidens n. sp. 



Plate IV, figs. 28-32. 



One of the most persistent and characteristic fossils of this formation 

 at the several localities where it has been recognized, and one that will 

 probably serve to identify it at other localities, owing to its marked features, 

 is a small species of Trilobite of the genus Proetus. Although specimens 

 of the pygidium have been obtained at all the localities yet recognized, no 

 other parts of the animal haA^e been noticed except from one locality. 

 These were collected, and sent, among other species, by J. E. Clayton, esq., 

 of Salt Lake City, from Dry Canon, Oquirrh Mountains, Utah. They 

 consist of some detached and imperfect examples of the glabella and cheeks ; 

 and as there are no other forms of Trilobites yet known from the locality, 

 and these occurring in the same blocks with the pygidia, it is reasonable to 

 infer that they belong -to the same species. 



The glabella is conico-cylindrical in form, once and a half as long as 

 wide, very gently narrowing from the base forward, and rounded-truncate 

 in front; very depressed-convex throughout, and marked by four pairs of 

 transverse furrows; the posterior ones strongest, curving backward at their 

 inner ends, nearly surrounding the posterior lobes, forming rounded convex 

 tubercles, each of which is equal in width to one-third that of the entire 

 glabella. The other three pairs are faintly marked, and reach nearly one- 

 third across the glabella; the anterior one transverse and very obscure, 

 distant from the anterior end of the glabella, equal to its width at the furrow; 

 second and third pairs distinct, slightly curving backward at their ends. 

 Occipital ring narrow, depressed-convex, and not strongly marked. Fixed 

 cheeks narrow ; palpebral lobe small, situated a little more than one-third 

 of the distance from the posterior border of the head, angular in outline. 

 Frontal border thickened and rounded, well defined, but not distinctly 

 separated from the glabella in front. Posterior lateral limbs not preserved, 

 but narrow at their junction with the fixed cheeks. Suture-line cutting the 

 frontal margin, with a slight curvature at a point distant from the sides of 



