Devonian Bocks. 93 



son published his " Silurian System," ten genera and seven- 

 teen species of fishes, and fifteen genera and twenty-three 

 species of mollusca, are enumerated by him as belonging to 

 the middle and lower Devonian beds. In the recent work 

 on Russia, M. de Verneuil enumerates forty-six species of 

 fishes and sixty-six species of mollusca, which he and his fel- 

 low-travellers found in the same group in that country. M. 

 Agassiz, in his " Monograph of the Fishes of the Devonian 

 System," raises the number of genera to forty-three, and of 

 species 105, belonging to six or seven families ; and he tells 

 us that Monte Bolca itself, hitherto reported to be the loca- 

 lity of all others most rich in species of fossil fishes, does 

 not contain a greater number ; adding, that, as only a com- 

 paratively small portion of the rocks of this system has been 

 examined, many additions may be expected. M. Agassiz is 

 shortly going, it is said, to North America, where he will 

 very likely discover many new forms. It is gratifying to 

 find him ascribing the main success of his researches in this 

 'field " aux recherches perseverantes et au zele infatigable 

 des geologues Anglais." 



But not only is there this great variety of genera and 

 species, but the number of individuals found in some locali- 

 ties immense. Thus, in some parts of Russia there are brec- 

 cias almost wholly composed of the scales and plates of the 

 Asterolepis, and the remains of the Pterichthys are so abun- 

 dant in the geodes of Lethen Bar, in Nairnshire, as to have 

 been collected in cart-loads. But our wonder is not alone 

 excited by the great variety and number of vertebrate ani- 

 mals of a high organization in strata so very low in the order 

 of formations ; there are many most remarkable features in 

 the history of this early part of the animal creation which the 

 researches of M. Agassiz have brought to light ; for these, 

 however, I must refer you to the work itself. 



M. Agassiz, in speaking of the lowest beds in which the 

 remains of fishes have been found, makes the following im- 

 portant observations on the probability of their existing in 

 still lower beds : — " If we have not yet been able to recog- 

 nize remains of fishes below the Lower Ludlow rocks, I do 

 not think that we ought from that to conclude that fishes do 



