UPPER AND LOWER. 119 



But the defensive spine of tlie Onchus Murchisoni, as exhi- 

 bited in one of the Ludlow specimens, measures, though 

 mutilated at both ends, three inches and five-eighth parts in 

 length. Even though existing but as a fragment, it is, as such, 

 nearly twice the length of the largest spine of the dog-fish 

 unmutilated and entire, and considerably more than twice the 

 length of the largest spine of the Port-Jackson shark. The 

 spines detected by Professor Phillips, in an inferior stratum 

 of the same upper deposit, were, as has been shown, of 

 microscopic minuteness ; and when they seemed to rest on 

 the extreme horizon of ichthyic existence as the most an- 

 cient remains of their kind, the author of the "Vestiges'* 

 availed himself of the fact. He regarded the little crea- 

 tures to which they had belonged as the foetal embryos, 

 their class, or — to employ the language of the Edinburgh 

 Reviewer — as " the tokens of Nature's first and half-abortive 

 efibrts to make fish out of the lower animals." From the 

 later editions of his work the paragraph to which the Re- 

 viewer refers has, I find, been expunged ; for the horizon has 

 greatly extended, and what seemed to be its line of extreme 

 distance has travelled into the middle of the prospect. But 

 that the passage should have existed at all is a not uninstruc- 

 tive circumstance, and shows how unsafe it is, in more than 

 external nature, to regard the line at which, for the time, the 

 landscape closes, and heaven and earth seem to meet, as in 

 reality the world's end. The Wenlock specimen, — a group 

 of palatal teeth, — though certainly not microscopic, is, I am 

 informed by Sir Philip Egerton, of but small size ; whereas 

 the contemporary spine of the Onondago Limestone, though 

 comparatively more a fragment than the spine of the Upper 

 Ludlow Onchus, — for it measures only three inches in length, 

 — is at least five times as bulky as the largest spine of Spinax 

 Acanthias. Representing one of the massier fishes disporting 

 amid the some four or five small ones, of which, in my illustra- 



