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section more intelligible. Subsequently we examined the bed containing 

 the Ammonites semicostatus, which, as before stated, is seen near the top 

 of the series. On the following day we were taken by Mr. Moore to a 

 coast section, where the lias was seen resting immediately upon the 

 mountaiu limestone. Here I found the Ostrea interstriata in great 

 profusion. It was growing on the floor of mountain limestone from 

 which the waves had removed the superincumbent lias, leaving it just 

 as when it flourished in the ancient sea of the Ehsetic age. This speci- 

 men, as I have just intimated, was found, not so much in the lias, as on 

 what was the bottom of the sea before the deposition of the lias; but 

 in the immediately overlying lias appeared, as Mr. Moore pointed out, 

 many Lima bed fossils. Amongst these, one of the most characteristic was 

 a species of Pentacrinite, P. vulgaris, Schl. 1 Here then, as at Bridgend, 

 the fossils of the Lima beds were found in close proximity to the Ehsetic 

 species, if not actually associated with them. On the following day we again 

 repaired to the Bridgend cutting, Mr. Moore haA^ng left us, and on this 

 occasion both Mr. Kirshaw and myself found specimens of Ammonites 

 angulatus, near the bottom of the series. Also Mr. Kirshaw picked up a 

 Gryphite on which were growing no less than six small specimens of Ostrea 

 interstriata. This specimen disposes of the whole question. At this locality, 

 at any rate, the two species are coeval. Both M}-. Moore and myself 

 were right and both were wrong. The Gryphite figured by Mr. Jones is 

 of the age of the lima-beds, but it is also of the age of the Ostrea interstriata, 

 What I have stated above will completely exonerate Mr. Jones from the 

 charge of inaccuracy in placing the Gryphite at the bottom of the South 

 Wales lias. But the present communication may seem incomplete if. 

 some explanation is not given why two species should be found together, 

 which should properly be considerably separated in time in the Liassic 

 deposits. It cannot be that the Rhsetic beds and those at the bottom of 

 the lower lias have been deposited, and then broken up and mixed with 

 the Lima beds at the period of the deposition of the latter, because in 

 that case we should have a simple mixture of the species, and not one 

 growing upon the other. I humbly submit that there is but one 

 solution, i.e., that during the period of the deposition of the Bhsetic beds 

 no such deposition took place at the locality in question, and the little 

 oyster continued to live until the Gryphite made its appearance on the 

 stage of life, and that both continued to live together for some time, the 

 oyster being the first to give way. I must apologize for the length 

 of this letter, and with youx permission subscribe myself, 



Yours very sincerely, 



EGBERT F. TOMES. 



