360 Canadian Record of Science. 



glabella, the shortening of the eyelobe, and the more pro- 

 fuse ornamentation of the test, are most noticeable in' those 

 species, whose remains are entombed in the fine dark-grey 

 argillaceous sediments, and least observable in those found 

 in coarse shale and sandstone. 



As regards the most salient characters of the five genera 

 above-named, they may be arranged as follows : — 



Genera having the most primitive suture . . < a o-raulos^ & US ' 



Genera most completely representative of J Liostracus. 

 the average characters of the group. ... 1 Ptychoparia. 



Genus exhibiting the widest departure / Q i,,,,,^!,,,™ 

 from the primitive type \ boleno P leura - 



How much is yet to be learned respecting the origin of 

 the Cambrian fauna! With the extensive and careful 

 researches which have been made during the last score of 

 years in the oldest sedimentary rocks, how little has been 

 accomplished toward piercing the wall of barren formations 

 that severs the Eozoon of the Laurentian system from the 

 earliest primordial forms ! It can hardly be that a fauna 

 which blossomed out into such a variety of types at the 

 base of the Cambrian System had there its beginning. 

 Here, in the Paradoxides Zone, the species of animals, both 

 in Europe and America, have a strong representative as- 

 pect, but only a limited number are found to be identical. 

 There is a similar, though not identical succession of forms, 

 in the several members or groups of strata which compose 

 this zone, as if a stream of new species were coming in on 

 both sides of the Atlantic; and yet certain genera which 

 are found in the deposits of one continent are not to be 

 met with in those of the other. With these facts before us, 

 the dictum that Life originated in the Primordial Zone 

 seems untenable. 



On the contrary, we are lead to surmise that at some 

 other point on the surface of the globe than any which has 

 yet been explored, the ancestors of the Primordial Fauna 

 will yet be found : it may be years before it shall be re- 

 covered, and in lieu of actual knowledge, inferences based 

 on the study of the embryological forms of the species of 



