136 
THE GEOLOGIST. 
COERESPONDENCE. 
Restoration of PUrdspis. 
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 suflfice 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. Rat Lankestee. 
PROCEEDINGS OE GEOLOaiCAL 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 certain 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 Bran caster 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 addi-essed to the Geolo- 
gical Society. 
