16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 1, 



4. On some of the Remains in the Bone-bed of the Upper Ludlow 

 Rock. By Sir Roderick I. Murchison, F.R.S. G.S. &c. 



In looking over the Woodwardian Museum of the University of Cam- 

 bridge last year, I perceived that Professor M'Coy had, among his 

 many skilful arrangements, discovered that a fossil from the Lower 

 Ludlow rock, which if detached I should have called an ichthyodoru- 

 lite, was one finger of the claw of a large crustacean analogous to the 

 Pterygotus of Agassiz ; an animal which, though at first classed with 

 fishes, was long ago removed by that author himself into the order of 

 Crustacea. 



In this case indeed there could be no mistake, for in the specimen, 

 which Professor M'Coy had then named Pterygotus leptodactylus, 

 one solid finger was seen to be closely attached at its base to an mi- 

 equivocal cast of the other, thus representing the claw of a small 

 lobster. 



Now although this body was taken, as above stated, from the Lower 

 Ludlow rock, it appeared to be very desirable that Professor M'Coy 

 should closely scrutinize some of the remains of the bone-bed of the 

 Upper Ludlow which had been referred by Agassiz to fishes. For, 

 as the great ichthyologist had formed his opinion from the drawings 

 only which I sent to him, and had never had an opportunity of look- 

 ing into the framework of those fossils with the microscope, it seemed 

 not unhkely that some of them might also prove to be crustaceans. 



I accordingly procured for the examination of Professor M'Coy the 

 specimens from the museum of the Geological Society which I had 

 originally placed there, and others from the cabinet of my friend the 

 Rev. T. T. Lewis. I regret to say that some of the most curious of the 

 fragments published in the ' Silurian System,' which were found by 

 the late Rev. R. W. Evans and beautifully arranged on cards by that 

 gentleman, are nowhere to be found. In respect to such forms the 

 naturalist can therefore only refer to the etchings of Mr. James 

 Sowerby and Mr. Salter ; and those I can testify (Mr. Lonsdale being 

 also a living witness) were most minutely accurate and faithful repre- 

 sentations of the originals. 



Professor M'Coy has been led to think that the Onchus tenuistriatus 

 (Sil. Syst.) is the only true fish-defence of the Upper Ludlow rocks, 

 the other fish-remains, Sphagodus and Thelodus (Ag.), being recog- 

 nized as the osseous particles of the shagreen or prickly skins of shark- 

 like fishes. The Plectrodus and Sclerodus (Ag.) as well as the 

 Onchus Murchisoni, are removed by him to Crustacea. 



On consulting Mr. Salter, who has communicated with Mr. Sow- 

 erby, I find that they cannot adopt this view. They necessarily bow 

 to the discovery made by Professor M'Coy, that three of the frag- 

 ments, figs. 10, 63, and 64, in plate 4 of the ' Silurian System,' which 

 were grouped with the Onchus Murchisoni, are really crustacean, and 

 have the thin hollow crust characteristic of that class ; but they hold 

 decisively to the opinion, that the figures 9 and 11 of the Onchus Mur- 

 chisoni represent true fish-bones ; Mr. Salter, who drew these two 

 specimens himself, having a distinct recollection of their thick solid 



