262 PALAEONTOLOGY. 



CRUSTACEA. 



Genus PROETUS Stein. 

 Pkoetus pkroocidens n. sp. 



Plate IV, tigs. 28-:!2. 



One of the most persistent ;ind cliaracteristic fossils of this formation 

 at the several localities whei-e 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 Proetm. Although specimens 

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

 other parts of the animal have 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 Ibrms of Trilobites yet known from the locality, 

 and these occiuTiog 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 g-ently 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 svirrounding 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 fuiTow; 

 second and third jjairs dislinct, slightly curving backward at their ends. 

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

 cheeks narrow; palp( bral lobe small, situated a little more than one-third 

 of the (listMiicc iVoui tile posterior border of the head, angular in outline. 

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

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

 but narrow at tlu^ir junction with the fixed cheeks. Suture-line cutting the 

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



