SI I.r HI AN A OK. 9 



sequent!) proposed genera. The other names applied },\ Cm-da fall into the list of 

 ynonynu, juri a> it'the\ had IK en proposed l>\ an\ other author at an\ subsequent 

 time. 



Owciii. 



Arlom.llui (rr<-;,,V./,Aa/iii) Ovmi, UKEK & lUti.px, I'roceed. Acad. Nat. Sol. Phlla., December, 1861, p. 43. 

 ArioHttlmtt thctni, UKKK It UATI.KX, Am. Jour. Bel. Bee. Bcr. XXXIII, 74, January, 1862. 



-. -mi . in-iilar, or nearly semlelliptic in outline, iU length equalling about two-third* its breaillh, rather dis- 

 tiiu-tly convex ; posterior margin more or \ea concave in outline, anil provided with a deep, rounded marginal 

 along each lateral slope. Glabella oblong-subovate, rather gibboat, elevated above the cheeks and tapering 

 towards th rounded front with slightly convex lateral margins ; greatest convexity near the middle and behind ; 

 separated from the cheeks, on each side and in front, by a distinct furrow ; neck furrow passing entirely across, but 

 >! i. litly !..-]. .TOII each .tide than at the middle ; lateral grooves three, very short, obscure, or (In casts) nearly obsolete, 

 :ui.i I. nt .-Ii.-litly ..l,li,|... (Yrvk-al segment a little convex at its posterior outline, less eliirated than the glabella, 

 .Aiit--n.il >1>(K- in advance of the glabella less than half as wide as the length of tin- latter, and provided with a 

 distinct, ronnilml transverse furrow, which pause's around slightly in front of the middle of the space parallel to 

 the anterior and antero-lateral margins. Cheek* convex, and sloping towards the lateral and autero-lateral bor- 

 ders. (Surface and facial sutures unknown.) 



Length of cephalic shield, measuring from the posterior side of the neck segment to the front margin, 0.57 Inch ; 

 greatest breadth, measuring across at the posterior extremities of the cheeks, 0.87 inch ; height, 0.31 inch. Length 

 of glabella, including the Deck segment, 0.40 inch ; breadth of glabella, 0.35 inch. 



D 



^^^ ^^^ llrld of Tounf 



Proal* view of haul. \M I I indindu.i 



Agraulut (lietnl. 



A. Side view of a cephalic shield of Ayrattloi Owtni, the position of the eyes (which have not been distinctly seen) 

 Indicated by a dotted line. 



/.'. Another view of the same, and of a sin.ill pygidinm supposed to belong to the name species, with the body restored 

 in outline. In this cut the marginal furrow pausing around the front of the head is made to terminate rather 

 too abruptly on each side; while the lateral furrows of the glabella are Indicated too distinctly. In the 

 specimens these furrows are very obscure, and it is difficult to see whether there were only two, or more on 

 each side. 



I'. Head of a young individual, same species. 



Tlu> only specimens of this species yet obtained are casts, which show no traces 

 of the sutures, and retain no remans of surface <rraiuilations, stria>, or other mark- 

 ings, if there ever were any. Nor are they in a condition to show whether or not 

 the jxjstero-lateral extremities of the hueklcr are pointed, though they probahly arc. 

 At a point nearly opposite the middle of the glahella, there is on each cheek, less 

 than half way down the slope from the furrow l>etwcen the fixed cheeks and the 

 glahella, the remains of a small eye, though the specimen heing unfortunately a 

 little defective here on both sides, the exact form of these prominences cannot 

 be clearly made out. 



In the same slab containing the cephalic shield above descrilx-d, we observe a 

 p)gidium which probably belongs to the same species. It is sub-semicircular in 

 form, moderately convex, and rather distinctly, as well as nearly equally trilobate. 



2 February, 1864. 



