1852.] MURCHISON SILURIAN FISH REMAINS. 17 



structure. Mr. Sowerby, who etched the jaws of the Plectrodus and 

 Sclerodus, has also no doubt, that, although they may pertain to one 

 genus, they are unquestionably fish jaws, as shown by fractures of the 

 solid bone which are represented in the figure (see fig. 61). Sclerodus 

 jpustuliferus (figs. 60, 61, 62) was drawn by Mr. Salter, who reminds 

 me of the cancellous structure of its broken end, and which he distinctly 

 recollects to have been quite unlike the shelly crust of the Pterygotus. 

 It is but justice, however, to Professor M'Coy to say, that he does 

 not consider the existence of this solid and cancellous texture a suffi- 

 cient reason to induce him to change his present opinion. 



Whilst, therefore, the discovery of Professor M'Coy has shown us 

 that one or more of the supposed fragments of fishes are really crus- 

 tacean, we may, it seems, continue in the belief that the greater part 

 of the remains are those of fishes. Let us hope that, as this bone- 

 bed has recently been found to re-appear from beneath the Old Red 

 Sandstone near Hereford, and has been traced by Mr. Strickland to 

 the southern extremity of the May Hill district, and even in 1 848 was 

 found by Professor Phillips at Pyrton Passage on the Severn, we may 

 be supplied with fresh specimens to replace the originals figured in the 

 * Silurian System,' and that by subjecting them to the microscope we 

 may for ever terminate all doubt. 



Again, as Professor M'Coy shows that there are remains of a shark- 

 like fish in this deposit, we may still consider the small, smooth, elon- 

 gated, and convoluted bodies, which were analysed by Dr. Prout, to 

 be the true coprolites of fishes. 



As the author of the Silurian System, I hope to be excused if I re- 

 mind my associates that the most assiduous researches in various re- 

 gions where the earlier groups of fossils have been widely spread have 

 failed in detecting anywhere a zone of higher antiquity than the Upper 

 Ludlow, in which the remains of fishes are imbedded. Thus these 

 venerable small ichthyolites are still, what I announced them to be long 

 ago, the most ancient known beings of their class * . These few traces 

 of fishes being detectable only at the close of the first long sera of pri- 

 maeval life, it follows that the Silurian deposits as a whole are promi- 

 nently separated from all those which succeeded, by the invertebrate 

 character of their very numerous fossil animals, among which the 

 cephalopods that so abound probably performed the duties of the 

 fishes and were the scavengers of the pristine seas. In all succeeding 

 systems and formations the remains of fishes are, as is well known, 

 found in association with other marine spoils. 



Having heard that Mr. Lewis of Aymestry had discovered an 

 ichthyodorulite in the Wenlock limestone, I procured the specimen, 

 which, being referred to Mr. Salter, Avas instantly identified as the 

 Ptilodictya lanceolata (Lonsdale), a coral published in the ' Silurian 



System.' 



* Sil. Syst. p. 606. 



VOL. IX. PART I. 



