Carboniferous Trilohites. TV) 



Lateral lobes moderately convex, with a slightly thickened, scarcely elevated 

 border of moderate width, on which the ribs become nearly obsolete. Axial 

 lobe marked by 9 rounded and distinct annulations, exclusive of the termi- 

 nal ones, strong in front and rapidly decreasing in size posteriorly. The 

 ribs of the lateral lobes are 10 in number on each side, simple, highly 

 rounded, and continuing entirely around tlie posterior margin of the shield, 

 the most posterior ones being very faintly marked." 



Geological posit io)i and locality. — Waveiiy group afc Logan 

 Caiion, Wahsateh Rauo-e, Uiali. __ 



PKOETUS PEKOCCIDENS, Hall & ^Vliitfield. 



Proetus peroccidens. Hall and Whitfield, 1877, U. S. Geol. Expl. 40th Par., 

 Vol. lY, p. 262, pi. 4. figs. 28-32. 



The authors give the following description of this species : " The glabella 

 is cc>nico cylindrical in form, once and a half as long as wide, very gently 

 narrowing from the base forward, and rounded-truncate in front ; very de- 

 pressed-con v^ex throughout, and marked by four pairs of transverse furrows, 

 the posterior ones stronger, curving backward at their inner ends, nearly 

 surrounding the posterior lobes, forming rounded convex tubercles, each of 

 which is equal in width to \ that of the entire glabella. The other three pairs 

 are faintly marked, and reach nearly'- \ across the gla-lDella ; 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 maiked. Fixed cheeks narrow ; palpebral lobe small, sit- 

 uated a little more than i of the distance from the posterior border of the 

 liead. angular in outline. Prontal border thickened and rounded, well de- 

 fined, but not distinct!}'- separated from the glabella in front. Posterior la- 

 teral 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 dis- 

 tant from the sides of the glabella equal to one-half its width at the anterior 

 end. and rounding inward with a gentle curvature to the anterior side of 

 the palpebral lobe, the cheek being very narrow at this point, thence pass- 

 ing along the top of the eye to the junction of the posterior lateral limb. 

 Surface of the glabella and cheeks smooth, except a few^ granules near the 

 base of the glabella. 



Movable checks of medium size in proportion to the glabella, flattened 

 convex from the base of the eye to the narrow, thickened, and chamfered 

 marginal rim ; occipital furrow narrow, not strongly marked, and reaching 

 nearly to the depression within the marginal rim ; posterior angles of the 

 cheeks extending backward in the form of short angular spines. 



Thoracic seii'ments unknown. 



