﻿1851.] 



SALTER ON SILURIAN FISH REMAINS. 



267 



upper surface of the Aymestry rock. But I have his authority for 

 saying, that he has never found any traces that he could rely on 

 below that parallel. 



And in these uppermost strata they not only occur in Britain, but 

 in other places. M. Barrande is about to publish large bony frag- 

 ments 6 or 8 inches long, obtained from the top of the Silurian 

 system in Bohemia. And the American geologists have figured and 

 described large defensive spines collected in their Onondago and Cor- 

 niferous Limestones, and some are mentioned even from the Oriskany 

 Sandstone. M. de Verneuil, it is true, would regard this last-named 

 stratum as the base of the Devonian system in America ; but whether 

 this interpretation be accepted, or that which seems most generally 

 the opinion in America, that these rocks belong to the Upper Silurian, 

 they do not warrant our believing that Fish-remains occur there so 

 far down as the parallel of our Wenlock limestone. 



But while thus endeavouring to show that there has hitherto been 

 no evidence published on which the existence of Fishes in the Lower 

 Silurian can be established, I have a new and very interesting fact to 

 communicate which makes their occurrence at this epoch a matter of 

 great probability. At the same time that the spurious fish-defence 

 was collected by the Geological Survey in North Wales, certain 

 rounded black substances, not above half an inch diameter, were 

 found with it, which suggested the idea of coprolites. These have 

 been since analysed in our laboratory by Dr. Playfair, who found 

 them to contain the very large proportion of above thirty per cent, of 

 phosphate of lime. This, then, would at once decide the question, 

 were it not for the occurrence, in more recent strata, of phosphatic 

 nodules of doubtful origin, since no substance is known at present 

 which could yield so large a quantity of this mineral except bone, and 

 that of vertebrate animals ; while its occurrence in the form of copro- 

 lite would point at least to Fish or some higher animal as its origin. 

 But it was of course necessary to ascertain whether the matrix was 

 impregnated with the phosphate or not, since the discovery by Dr. 

 Daubeny of large veins of this substance in the older slate-rocks of 

 Spain is so well known. Dr. Playfair has therefore analysed the 

 limestone of Rhiwlas* near Bala, in which these black bodies were 

 found ; but although the rock is so charged with organic remains as 

 to yield two per cent, of animal matter, not a trace of the phosphate 

 presented itself. The conclusion, therefore, seems almost inevitable, 

 that animals of a high organization, and most probably, therefore, 

 Fish, existed during the deposition of the Llandeilo flags. 



The point of earliest appearance of any of the great divisions of the 

 animal kingdom is of course a subject of deep interest to the geologist, 

 and even more so to the naturalist. That there has been a gradual 

 development of the higher forms of life as we ascend in the series, at 



* I should like to call the attention of geologists and tourists to this remarkably 

 rich locality, where certainly the rarer fossils of the Lower Silurian rock are to be 

 found more plentifully than in any other locality. The entire pelvis of some large 

 Encrinites would reward careful work, and great numbers of Trilobites, spiral 

 shells, and Orthoceratites are to be met with. Cystideans also of six or eight 

 species abound there. 



