142 Correspondence—Mr. T. MW. Reade—Mr. Clement Reid. 
Tomognathus mordax, Dixon. [ Lom. lecodus, Dixon. ] 
Elopine Clupeoid, gen. non det. 
Incert# SEDIS. 
Celorhynchus cretaceus, Dixon. 
Ancistrodon, sp. 
Pelecopterus spectabilis (Agass.), Cope. [Ptychodus spectabilis, Agass. | 
48 gibberulus (Agass.), Cope. en gibberulus, Agass. | 
ui arcuatus (Agass.), Cope. 46 arcuatus, Agass. | 
‘5 (?) articulatus (Agass.), Cope. [- ,, articulatus, Agass.] 
The author also pointed out that the type specimen of Strophodus 
asper, Agass., is a fragment of a Orustacean; that the so-called 
Orthagoriscus-jaw (Dixon) is the dentary bone of a Chelonian; that 
Selache Daviesii, Hasse, is founded upon a vertebra of Ptychodus ; 
and that the so-called premaxilla of Enchodus is really the palatine 
bone. 
CORRESPONDENCE. 
a 
THE DIMETIAN OF ST. DAVIDS. 
S1r,—The geology of St. Davids will, I fear, never be settled by 
petrological methods. Recognizing this, I based my interpretation of 
the so-called Dimetian principally upon the relation and disposition of 
the various groups of rocks composing the peninsula of St. Davids. 
The result of my examination was to lead me to believe that by no 
known system of faults and folds could the “ Dimetian,” if a pre- 
Cambrian body, have been placed in its present relations with the 
surrounding rocks. This is my main contention, and all the remain- 
ing arguments are subsidiary, and in value only relative. As I 
have already developed these views in detail in a paper just read 
before the Liverpool Geological Society, I need not further dwell 
upon them here. 
It is very far from my intention of entering upon a controversy 
upon this question, most of all from a petrological standpoint. On 
a re-perusal of the literature on this subject, I find that Dr. Hicks 
formerly described as shales interbedded in the Dimetian what he 
now considers to be Diabase Dykes. 
I may be quite wrong in my view that the veins in question are 
included Cambrian shales; but until I have an opportunity of 
re-examining the district, I am not prepared to admit his contention. 
Parxk CornER, BLUNDELLSANDS, T. Mretiarp Reape. 
11th January, 1888. 
THE EXTENT OF THE HEMPSTEAD BEDS, Etc. 
Sir,—Writing in the Isle of Wight,’ with no library available, I 
find I have overlooked a paper by Dr. E. P. Wilkins, F.G.S. As 
long ago as 1861 he recorded a section of Hempstead Beds in the 
Medina (see Proc. Geol. Assoc. vol. i. p. 194). 
Ciement ReErp. 
1 Grou. Mac. Nov. 1887. 
