398 



Prof. P. M'Coy on the Classification of 



Faceted pleitrcs of Trilohites. 



a, Calymene ; h, Ellipsocephalus ; c, Asaphiis ; d, Phacops; e, Odontochile ; 

 /, Dysplanus; g, Illaenus; h, Forbesia ; i, Homalonotus ; k^ Trimero- 

 cephalus. 



*TIk iililik lililito^ liilite^ ..rfiiaafeK 





Nonfaceted pleurcE of Trilohites. 



/, Ogygia; m, Lichas; n. Bronteus ; o, Ampyx ; p, Harpes; q, Conocepha- 

 lus ; r, Paradoxides ; s, Zethus; t, Cryphaius; u, Acidaspis; v, Stau- 

 rocephalus ; w, Olenus ; x, Trinucleus ; y, Ceraurus. 



^'~\::;:: — i Z 6 \ IS 1 -r 



10 



4. Harpedime ; 5. Agnostince. The British genera would arrange 

 themselves as follows, and where the value of any of the groups 

 was not previously settled, I have added a few explanatory words. 



1st Subfam. AsAPHiNiE. 



Pleurae bent down at the ends, each with a distinct trigonal facet 

 at the anterior edge. 



These are the most perfectly organized Trilohites ; they have 

 a compact ovate form, and from the deflexion of the margin are 

 of considerable depth ; they all, I believe, have the power of roll- 

 ing into a ball, and are the only Trilohites having the triangular 

 facets at the anterior edges of the ends of the pleurae. The fol- 

 lowing are British genera and subgenera : — 



Gen. 1. Phacops [in a wider sense than Emmerich). Lateral ce- 

 phalic angles prolonged backwards ; glabella wider in front 

 than at base ; sides with three large segmental furrows ; eyes 



