Ck. XXVII. ] ABSENCE OF FISH IX LOWER SILURIAN. 455 



They who in our own times have explored the bed of the sea inform 

 us that it is in general as barren of vertebrate remains as the soil of ? 

 forest on which thousands of mammalia and reptiles may have flourished 

 for centuries. In the summer of 1850, Professor E. Forbes and Mr. 

 McAndrew dredged the bed of the British seas from the Isle of Portland 

 to the Land's End in Cornwall, and thence again to Shetland, recording 

 and tabulating the numbers of the various organic bodies brought up by 

 them in the course of 140 distinct dredgings, made at different distances 

 from the shore, some a quarter of a mile, others forty miles distant. The 

 list of species of marine invertebrate animals, whether Radiata, Mollusca, 

 or Articulata, was very great, and the number of individuals enormous ; 

 but the only instances of vertebrate animals consisted of a few ear-bones 

 and two or three vertebrae of fish, in all not above six reHcs. 



It is still more extraordinary that Mr. McAndrew should have dredged 

 the great " Liug Banks" or cod-fishery groviids off the Shetland 

 Islands for shells without obtaining the bones . r teeth of any dead 

 fish, although he sometimes drew up live fish from the mud. This 

 is the more singular, because there are some areas where recent fish- 

 bones occur in the same northern seas in profusion, as I have shown 

 in the " Principles of Geology" (see Index, " Vidal") ; two bone-beds 

 having been discovered by British hydrographers, one in the Irish sea, 

 and the other in the sea near the Faroe Isles, the first of them two, and 

 the other three and a half miles in length, where the lead brings up 

 everywhere the vertebras of fish from various depths between 45 to 

 235 fathoms. These may be compared to the Upper Ludlow bone- 

 bed ; and on the floor of the ocean of our times, as on that of the 

 Silurian epoch, there are other wide spaces where no bones are imbedded 

 in mud or sand. 



It may be true, though it sounds somewhat like a paradox, that fish 

 leave behind them no memorials of their presence in places where they 

 swarm and multiply freely ; whereas currents may drift their bones in 

 great numbers to regions wholly destitute of living fish. Such a state of 

 things would be quite analogous to what takes place on the habitable 

 land, where, instead of the surface becoming encumbered with heaps 

 of skeletons of quadrupeds, birds, and land-reptiles, all solid bony sub- 

 stances are removed after death by chemical processes, or by the 

 digestive powers of predaceous beasts ; so that, if at some future period 

 a geologist should seek for monuments of the former existence of 

 such creatures, he must look anywhere rather than in the area where 

 they flourished. He must search for them in spots which were co\- 

 ered at the time with water, and to which somes bones or carcases 

 may have been occasionally carried by floods and permanently buried in 

 sediment. 



In the annexed Table, a few dates are set before the reader of the 

 discovery of different classes of animals in ancient rocks, to enable him 

 to perceive at a glance how gradual has been our progress in tracing 

 back the signs of Vertebrata to formations of high antiquity. Such facts 



