SYNOPSIS OF GEN Ell A. 



xlv 



P. ovifrons being almost extinct), it becomes manifest!}' impossible to ascribe 

 even a sab-generic value to such variations. 



Tbe sub-genus Phaeton was proposed by M. Barrande, in 1846, for forms 

 of Proetus in which the pygidium bears a marginal fimbria caused by the ex- 

 tension of the annulations. 



Forbesiu, McCoy, 184G (Proetus concinnus, Dalman, type), is a Proetus in which 

 but two pairs of lateral furrows have I n observed. 



Celmus, Angelin, 1878 (C. granulatus, Aug.. type 1 ), is founded upon an ex- 

 ample in which there are twelve thoracic segments and bul two pairs of lateral 

 furrows. These last two genera are as yet imperfectly known, and may prove to 

 include species showing a structure intermediate between thai of the true 

 Proetus and of Cyphaspis. 



Genus PH AETHON I D ES, Angelin. L878. 



1835. Asaphus (partim). Mi si hison. Silurian System. 



1S4T). Proetus (partim), Loves. Ofversigt. af. Kong-1. Vetensk. Akad Eorhandl. 



1S4B. Phaeton, Barrande (*). Notice pie"liminaire sur les Syst. Sil. Bohi 



1M7. Prionopdtis, Corda (?). Prodrom Monog. bohm. Trilob. 



1852. Proetus (Phaeton), Barrande I !). Sj 3t. Sil. Boheme. vol. i. 



L863. /'■■ rtiin), Billikgs. Dev. and Silur. Foss. Square Lake, Me. 



\-::. Proetus (Pha ton), Mkbk. 1 . s. Geol. Suiv. Expl, Fortieth Parallel. 



1S7S. Phaethonides, Angelin. Pal: Sc mdinavica. 



1SS5. Phaeton, CEhlert. Bull, de la Soc. d'Etudes Scientif. d'Ang 



Diagnosis. Cephalon as in Cyphaspis, the fron- 

 tal area, however, being more deeply concave, 

 and the lateral glabellar furrows stronger and 

 generally duplicate. Thorax composed of not less 

 than seven narrow segments, and probably more. 

 Axis wide. Pygidium Proetoid, relatively large, 

 bearing from eight to twelve annulations upon 

 the axis, and eight or nine upon the pleura?. 

 These annulations extend to the margin, and 

 are conspicuously duplicate their entire length. 

 Surface tubercled or smooth. 



