[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 61 



This species differ from 0. prmus, Wale., in its broader glabella and 

 semi-circular pygidium, with the rachis not reaching the hind-border.' 



Oryctocephalus is evidently related to Paraboliua and Parabolinella 

 of the European Upper Cambrian ; it is a form of the Olenida^ which has 

 retained certain larval characters that are absent from the related genera 

 in Europe, as the extended eye-lobes, and perhaps the pits in place of 

 furrows on the glabella. Such pits are seen in the young of Ceratopye 

 forficula, Sars., but not in the adult. ^ 



In its general aspect Bathynotus holopyga, Hall, is much like 0. 

 Walkeri ; both have a glabella extending to the front margin, prolonged 

 eye-lobes, narrow free cheeks and extravagantly long genal spines. 

 Other points of resemblance may be noted. ^ 



Four examples of this species were found. 



1 have much pleasure in dedicating this species to Mr. B. E. Walker, 

 in whose collection the first example was found.* 



Age of the Fauna. 



Dr. Roeminger went no farther in determining the age of these 

 fossils than to say that they were " primordeal." Mr. Walcott who sub- 

 sequently examined the fauna determined that it should be referred to 

 the upper portion of the Middle Cambrian, and compared it to a fauna 

 which he had determined to be of this age.^ The correlation is based on 

 several species of this fauna that he had described, and which are found 

 in the Mount Stephen Fauna. Of these may be mentioned Zacanthoides 

 spinosus. Bathyurisciis Howelli and the species referred to Olenoides 

 Nevadensis \_Neolenus serratus.'] Other species occur at Mount Stephen, 

 but on the basis of the above species the fauna is determined to be of the 

 age of the upper part of the Middle Cambrian. As Mr. Walcott claims 

 that the Middle Cambrian is essentially the Paradoxides Zone I am com- 

 pelled to dissent from this decision, for I think the fauna much younger, 

 and base this view on a consideration of the genera of trilobites present. 



1 The pygidium assigned to O. primus is very like that of Cheirurus foveolatus, 

 Ang. Ill view of the known tail-shield of 0. Walkeri it seems doubtful if this 

 pygidium is properly placed. (See Brogger, " Die Silurischen Etagen 2und 3," pi. ii., 

 fig. 5.) 



'^ Die Silurischen Etagen 2 und 8, pi. iii., fig. 16. 



3 U. S. Geol. Surv. Bull. 30, pi. xxxi., fig. 1. 



* Since the above was put in type, Mr. H. F. Cowper Reed has published in the 

 Geological Magazine, London, August, 1899,.the description of a new species of Oryc- 

 tocephalus {O. Rcynoldsi) from the Mt. Stephen Fauna. It would seem however to 

 be a different species from the above. It has shorter genal spines and broader 

 movable cheeks ; the pygidium is longer, is composed of more numerous somites, 

 and has a pair of spines that much exceed the others in length. The species also is 

 somewhat longer than Mr. Walker's. 



î» Am. Jour. Soi., 1888, vol. xxxvi., p. 164. 



