44 



the articulations of the middle lobe, " are sometimes 

 simple or undivided, at least in the post abdomen, 

 but that they are always bifurcated in the Calymene" 

 As far as our observations have extended, these re- 

 marks do not apply either in the one case or the 

 other. 



The head or buckler of the rfsaph, is not so deeply 

 divided into three lobes as the Calymene; they are, 

 however, quite distinct. The oculiferous tubercles 

 are in some species exceedingly well marked by a re- 

 ticulated structure. 



This genus often occurs at the same localities with 

 the Calymene, though in some instances it seems to 

 occupy rocks peculiar to itself. Dr. John Bigsby, in 

 his list of organic remains occurring in the Caiiadas, 

 states, that he never found a single species of the 

 genus Calymene, on the north side of the River St. 

 Lawrence, although the Asaphs were very abundant.* 

 In his Sketch of the Geology of the Island of Mon- 

 treal, he however observes: " Of Trilobites, the 

 Asaph genus is the most abundant, they approach 

 nearest the species caudatus, of Brongniart. I have 

 found no entire Calymene, but many bucklers or heads 

 of the Blumenbach species, some of them an inch 

 and a half in diameter. They are found whole in 

 considerable numbers in the vicinity of Quebec. "f 



* Silliman's Journal, vol. viii. p. 83. 



t Annals New York Lyceum, vol. i. p. 214. 



