32 The Treasures of Siluria. [Jan., 



argument to assume that the old ideas are correct, until they have 

 been proved to be erroneous. The onus p-obandi lies with Dr. 

 Bigsby, and he has not advanced a single argument in support of 

 his novel classification. 



We can allow ourselves to notice but one other conclusion of 

 our author in connection with the Primordial Zone, and that only in 

 relation to the general question of the origin of life. Dr. Bigsby 

 remarks, " The Primordial stage did not start forth, Pallas-like, at 

 once, in full maturity."* This is quite true. In the Llanberis 

 or Bangor slates no fossils have hitherto been discovered, while in 

 the Harlech Grits above, the number of species, and of represented 

 genera, though certainly small, is somewhat uncertain, from the 

 bad state of preservation of many of them ; but in the still higher 

 Maenevian group we meet with a tolerably rich and varied fauna. 

 Dr. Bigsby 's idea is, that "the quantity, variety, and high rank 

 of its fauna shut us up from any other conclusion than that it Ls 

 only part, and a rich part, of an already established flora and fauna 

 lying undetected at present." f No doubt this inference is very 

 just, and it is certainly one in which we cordially agree ; but we 

 feel some difficulty in reconciling it with our author's dictum of the 

 necessity of " Kadiata, Mollusca, Annehda, Articulata, all showing 

 themselves simultaneously, or nearly so." % 



The first appearance of species, however, the author discusses 

 very briefly. It is, in truth, a subject on which very few facts can 

 at present be quoted. His proposition that " life started into 

 being, necessarily, in societies both composite and simple," § besides 

 appearing to contradict one of his inferences respecting the Prim- 

 ordial fauna, will probably not meet with general acceptance, 

 although the exact meaning to be ascribed to it seems to us a Httle 

 doubtful. 



Leaving this speculative subject, we will examine some of the 

 many curious facts which illustrate the duration of species, which 

 is a matter of very high interest. For instance, M. Barrande has 

 shown 11 that 32 species of Bohemian Orthoceratites began and 

 ended their existence in one subdivision of the Silurian rocks 

 (E.e.l), while 38 more passed up into the next stage (E.e.2), 

 and there perished. In this latter formation no less than 199 

 species of the same genus make tlieir appearance, not one of which 

 passes up into the overlying stratum. 



In connection with this subject it will be useful to draw 

 attention to Dr. Bigsby 's census of the species which are known 

 from only one place,1[ as compared with that of the total number 

 of Silurian species, viz. : — 



* r. XX. t I^i'l- t I*- xxxvii. § Ibid. 



II Sco 'Tlicsaurus,' p. xxxviii. t ^P- vii. and xxxvi. 



