On Cordania, a Proposed New Genus of Trilobites. 



By John M. Clarke. 



In the Palaeontology of New York, volume vii, 1888, certain 

 cephala and pygidia of trilobites from the Upper and Lower 

 Helderberg and Hamilton groups of various localities in the 

 State of ISTew York and elsewhere were tentatively referred to the 

 genus Phaethonides as defined by Angelin. A careful restudy of 

 these fossils and review of the literature pertaining to them, educes 

 the fact that Angelin included under his redefinition of this term 

 Phaethonides, forms which Barrande, the author of the name, never 

 intended to bring into so close association, and which can not be 

 properly regarded as congeneric. 



The name Phaeton was introduced by Barrande in 1846* for a 

 genus of trilobites, built on the general plan of Proetus, but 

 having a dentate pygidium. The type of the group was Phaeton 

 Archiaci, from the etage E. This name, however, had been used 

 by Brisson in 1770 for a genus of birds. In 1847, Cordaf 

 observed this fact of synonymy and substituted for Barrande's 

 term, the name Pkionopeltis. He defined the groups clearly and 

 at length, describing all the parts of the animals, and subdivided 

 his twelve species into two principal groups : A, those with 

 simple, uncarinate cephalic margin; B, those with this margin 

 carinate ; and of these groups the first was divided into those (a) 

 with 8 lateral pygidial spines, (b) with 7, (c) with 6 or 5 such spines. 

 An excellent illustration was given of the species P. Poly dor us, a 

 member of the second division of the first group, though the 

 first species of his typical group is his P. Priamus. In the first 

 volume of the " Systeme silurien du Centre de la Boheme," in 1852, 

 Barrande did not formally withdraw his term Phaeton, nor 

 acknowledge its preoccupation. He there retains the term in a 

 subgeneric sense, using it as equivalent to his " Groupe B " 



* Notice pr61imlnalre sur le systeme silurien etles Trilobites de Bohdme, p. SI. 

 t Prodrom einer Monographle der Bohmischer Trilobiten, p. 189. 



