136 



THE GEOLOGIST, 



CORRESPONDENCE. 



Restoration of Ftt r ispis. 



My dear Sir, — I should like, with your permission, to make a remark 

 upon the Rev. Hugh Mitchell's interesting letter and sketch of Pteraspis. It 

 seems to me that the specimen there sketched agrees with Professor Hux- 

 ley's restoration (given in a former letter) in all particulars, saving the ab- 

 sence of lateral cornua, the form of the terminal angles, and the presence of 

 the two large apertures which Mr. Mitchell has drawn in his letter. -These 

 differences are, I think, to be accounted for by the imperfect condition of 

 Mr. Mitchell's specimen. I have seen some hundred specimens of Pteraspis 

 with the lateral cornua and with no posterior apertures, but in every point 

 agreeing with Professor Huxley's restoration. I have also seen some hun- 

 dreds of specimens in a fragmentary condition, showing no cornua, no 

 spine, no rostrum, and often showing apertures in the test, caused by frac- 

 ture ; but most palaeontologists will, I think, agree with me in considering 

 the more perfect specimens as indicating the true form of the shield of 

 Pteraspis, and will attach no weight to the negative evidence of imperfect 

 specimens. The restorations of Pteraspis given by Mr. Mitchell in May 

 last, differ as much from the present one as it does from Professor Huxley's. 

 In the former restoration there was no rostrum and no spine ; but the dis- 

 covery of fresh specimens has shown that the Scottish Pteraspides did 

 possess spines and rostra like their English brethren. No doubt a little 

 time will suffice to show that they also possessed lateral cornua and a form 

 of the central disk, in nowise differing from that of the English specimens. 



With regard to the under surface of the head of Pteraspis, even the 

 great abundance of specimens in Herefordshire has afforded no evidence, 

 save that of a negative character, and it seems to be a fair conclusion that 

 it was unprotected ; the mouth being placed as in the sturgeon, and per- 

 haps of the same suctorial character. I may observe here, that in August 

 last I obtained the first specimen of the scales of Pteraspis, from a quarry 

 in Herefordshire. They are similar to those of the dorsal series of Cepha- 

 laspis, and are attached to a portion of the cephalic shield.* 



Truly yours, 



E. Ray Lankester. 



PROCEEDINGS OE GEOLOGICAL SOCIETIES. 



Civil Engineers. — January 26. — " On the East Coast between the 

 Thames and the Wash Estuaries." By Mr. J. B. Redman, C.E.— The ob- 

 ject of this paper, like that of 1852 on the South Coast, was to describe the 

 characteristics of a range of coast within cer tain limits, to trace the changes 

 produced by constant natural causes, and the resultant influences on the 

 various harbours ; those of Harwich, Orford, Southwold, Yarmouth, Blake- 

 ney, Wells, and Brancaster being mainly dependent on such natural bar- 

 riers as those described ; as also their improvement, or deterioration, which 



* A communication on the discovery of these scales has been addressed to the Geolo- 

 gical Society. 



