THE DEVONIAN PERIOD. 467 



ous, and Conocardium (Fig. 208, i), distinguished by the flattening 

 of one end and the protrusion of the other, reappeared, having been 

 absent from the Helderberg and Oriskany, after being represented 

 by several species in the Silurian. 



The revival of the trilobites. — Trilobites were present in more 

 than half a hundred species, a notable increase over the known species 

 of the same region in the preceding epoch. The presence of a remark- 

 able number of highly ornamented species was a conspicuous feature. 

 Spines, nodes, and granulations freely diversified their somewhat 

 erratic forms. The dalmanites led in this decorative movement, 

 though the species here represented (Fig. 208, k) is a modest form. 

 As far back as the Niagara, this genus had shown its ornamental ten- 

 dencies, but it only reached its maximum display in the Onondaga 

 epoch. Its chief rivals in these lines were the acidaspids and lichads. 

 Other crustaceans were but sparingly represented, the barnacles alone 

 having been found thus far. 



Other forms. — Of other types, there were annelids, sponges, hydro- 

 zoans, bryozoans, and probably protozoans, all of which played incon- 

 spicuous though, in the economy of the whole, doubtless not unim- 

 portant parts. 



The foregoing sketch has been based essentially upon the aspects 

 presented by the Onondaga fauna as found in the eastern interior basin. 

 In the James Bay region its facies is not well known. Corals were a 

 conspicuous element and the identification of the fauna has been based 

 chiefly on them. Fishes were also present there, a fact to be noted 

 in view of the question of their previous home. No capulids, or gas- 

 tropods of any kind, have been reported. Their absence may be 

 attributed in part to the smallness of the collections — for the entire 

 absence of gastropods is highly improbable — but their presence in 

 great abundance, as in the Helderberg and Oriskany faunas, is equally 

 improbable, and the most reasonable conclusion is that the gastro- 

 pods were but an inferior element in the James Bay fauna, and that 

 the large gastropodous factor of the Onondaga of the interior sea was 

 derived from the Oriskany fauna already in possession of the ground 

 when the succeeding invasion took place. This is supported by the 

 resemblances already noted. 



We have no evidence that any of the distinctive species of the 

 Onondaga fauna lived in the South American region, where certain of 



