232 Proceedinrjs of the Royal Physical Society. 



huroh Museum, and amongj them I found a small cranial 

 shield, wliich, being obviously referable neither to Cephalaspis, 

 nor to Pteraspis, nor to Scaphaspis, was rather puzzling in its 

 appearance. Being, however, at the time specially engaged 

 w^ith other subjects, this shield, from Cradley, lay rather 

 neglected, till one day I bethought me of it when examining 

 our collection of fish remains from the Devonian rocks of 

 Canada, and I was then greatly interested to find that the 

 English fossil was in reality a Coccostean, and a Coccostean 

 not of the type of Coccosteus decipieiis, but of Phlyctcenaspis 

 Acadicus. This is of special geological interest, seeing that 

 both in England and Canada this type is associated in the 

 same beds with Cephalaspis, whereas not a trace of any 

 Cephalaspidean has ever occurred in tliose northern Old Eed 

 Sandstone deposits (Orkney, Caithness, and Moray Eirth) in 

 which the typical Coccosteus is abundant. Nor does Coccos- 

 teus occur in Eorfarshire, where Cephcdaspis is characteristic. 



At the time I made this discovery no one seemed to know 

 of the existence of a Coccostean in the Cradley beds, though 

 indeed a piece of the shield of this very species is figured by 

 Lankester in his " Monograph of the Cephalaspidse " (pi. viii., 

 fig. 4) as a " fragment of doubtful character " in connection 

 with Zenaspis Scdvjeyi} However, a short time after com- 

 municating with Mr Smith Woodward on the subject, I 

 received a letter from that gentleman informing me that he 

 had since discovered, in the stores of the British Museum, 

 quite a number of specimens apparently identical with that 

 to wliich I had referred. He also kindly forwarded to me a 

 plaster cast of one of them, as well as outlines in pencil of 

 two others. 



In PI. XII., Eig. 3, I have given a sketch of the specimen 

 in the Edinburgh Museum. It measures 14~ inches in 

 length, and in general form resembles the cranial shield of 

 P. Acadicus, except that at the back it is more produced 

 outwards, as in Coccosteus, the postero- and antero-external 



^ Mr Win. Davies seems to have believed in the occurrence of " Placo- 

 devmi" in the Herefordshire beds, as he labelled some fragments in the 

 British Museum '^ Pterichthys." They do not, however, belong to that 

 lienus. 



