20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



Monocheilus anatinus (Hall) 



Conocephalitcs anatinus Hall, i6th Ann. Rep. New York State Cab. Nat. 



Hist., p. 158, pi. 7, figs. 34, 35, 1863. 

 Conaspis anatina Hall, idem, p. 152. 

 Conaspis anatina Walcott, Smithsonian Misc. Coll., vol. 57, no. 13, p. 357, 



1914. 



Upper Cambrian, Franconia; Trempealeau, and other localities in 

 Wisconsin. 



Holotypc. — A.M.N.H. no. 329; cast, U.S.N.M. no. 89931. 



Monocheilus micros (Walter) 



Conaspis micro Walter, Iowa Geol. Surv., vol. 31, p. 185, pi. 11, figs. 5, 6; 

 pi. 12, fig. 2, 1926. 



Upper Cambrian, Franconia ; 3 mile southeast of Lansing, Iowa. 

 Holotype. — Univ. Iowa no. 9239. 



ONCHOCEPHALUS, n. gen. 



A group of trilobite species lies between the genera Inglefieldia 

 and ProUostraciis on the one hand, while on the other hand there 

 are features like Ponlscnia, Antagmus. Considered in another sense 

 these forms are about midway between Syspacephalus and another 

 new genus being described in a paper on the southern Appalachians. 

 For a long time the question was repeatedly considered from all angles, 

 and finally the conclusion was reached that matters would be simplified 

 if another genus were added. In order to stress the features separating 

 the new genus from those mentioned above, the name Onchoccphalus 

 was chosen to center attention on the development of the brim. 



Diagnosis. — Small trilobites in which the cranidium is usually 

 longer than wide. Glabella rather wide, slightly tapered, truncated in 

 front. Glabellar furrows faintly shown to the anterior end of glabella. 

 Contrary to the usual structure in this genus, the anterior pair is more 

 deeply impressed than the others. Fixigenes of nearly even width 

 throughout. Brim of variable width, but always well developed. Pre- 

 glabellar area convex, but variable in width; rim heavy, sometimes 

 greatly expanded, particularly in the center. Eyes small, situated 

 somewhat behind the midpoint of the glabella. Eye lines present. 



Genotype. — Ptychoparia thia Walcott. 



Namie. — oy/cos = protuberance ; Ke<^aAos = head. 



Onchocephalus thia (Walcott) 



Ptychoparia thia Walcott, Smithsonian Misc. Coll., vol. 67, no. 3, P- 96, pl. 

 12, fig. 6, 1917. 



