xl 



SYNOPSIS OF GENERA. 



Sub-genus ARGES, Goldfuss. 1839. 



vol. xix. 



1837. Calymene, Grben. Am. Jour. Science. 



[g3g .1 N \ii. Acad. Caes. Leop. Car. 



[843 J ,, . i,, i ■ . ■ . . Neues Jarhb. fttr Min. 



Lichas, Barrandb. Notice prelim, sur le Syst. sil. Boheme. 



184P. A rges, Bey rich. Untersuchungen lib. Trilob. 



[S47. Chrydoi < ' >pyge, part im, Corda. Prodrom Monog. bohm. Trilub. 



1852. Arges, Hall. Pal. N. Y., vol. ii. 



1852. Lichas, B Syst. Sil. Boheme, vol. i. 



1851 Lichas, Nibszkowski. Monog. Trilob. Ostseeprov. 



IS58. Lichas, Hoffmann. Trilobit. Russlands. 



1878. Lichas, Angblin, Palseontologia Scandinavica. 



1885. Arges, Schmidt. Revision Ostbalt. Silur. Trilob. 



Diagnosis. Middle lobe of the glabella 

 sub-rectangular, longitudinally arched, often 

 spiniferous. Second lateral lobes larger than 

 the first ; third lateral lobes inconspicuous or 

 obsolete. Palpebral furrows indistinct. 



Sub-gentjs C E R A T L I C H A S , n. sub-gen. 



Diagnosis. Frontal lobe ellipsoidal and 

 strongly convex, faintly constricted on the 

 abrupt and almost vertical posterior slope. 

 The elevated posterior edge of this lobe bears 

 two or four long recurved spines. The lateral 

 lobes are very depressed and obsolescent, the 

 first and second pairs coalesced, and the third 

 pair either obsolete or represented by faint 

 tubercles in the occipital furrow. Just within 

 eacb palpebral lobe is a slender spine, and 

 the occipital ring bears a long central recurved double spine. 



' atolichas differs from Conolichas, Dames, in the depressed and obsolete lateral 

 lobes: from Terataspis, Hall, in the sub-quadrate, slightly constricted frontal 

 lobe, ami from Arges, Goldfuss, in having the frontal lobe shorter, more ele- 

 vated, and abruptly sloping toward the posterior extremity. 



