100 R. F. Tomes — Palceozoic Madreporaria. 



outside of the corallum. Their denticulations bear but little re- 

 semblance to those of" the AstrmdcB and Fungidce, and more nearly 

 resemble undulations of the septal margin than actual denticulations, 

 and they may be due to the want of continuous development 

 incident on an open-work septum, rather than to the termination of 

 vertical columns or ridges, as in so many of the Astrceidce. 



When worn down, this coral assumes a different aspect. The 

 calice is then distinctly tri-areal. There is the outer ring of spongy 

 endotheca, an inner circle across which the septa pass, and a large 

 central columellary space of spongy tissue. 



The largest specimen I have seen has a height of one inch, and 

 a calice of half that diameter. 



It occurs in the Upper Silurian formation at Woolhope and Wen- 

 lock, but I have only met with a limited number of specimens from 

 those localities. 



By an error in transcribing M'Coy's description of Cyaihaxonia 

 Siluriensis, MM. Milne Edwards and Haime give it sixty or seventy 

 septa instead of sixteen or seventeen,^ and the error has been re- 

 peated in their general work on Corals.^ 



Cyathaxonia Dalmani, MM. Edwards & Haime, Mon. Polyp. Eoss. 

 des Terr. Pal^on. p. 322, pi. i. fig. 6. 



In a Silurian quarry at the west foot of the hill at the back of the 

 mansion at Old Col wall, Herefordshire, the residence of Mrs. Holland, 

 I found, on the occasion of a visit there, a considerable number of 

 small corals which could not be referred to any known English 

 species, but which, on examination, proved to be identical with the 

 Cyatliaxonia Dalmani of MM. Milne Edwards and Haime. 



The strata at the place mentioned are nearly vertical, and I was 

 unable to ascertain the position of the corals in them, though, from 

 the manner in which they were clustered in some of the nodular 

 lumps of stone lying in the bottom of the quarry, I did not doubt 

 that they were confined to one bed or zone. The quarry, so far as 

 I can ascertain by reference to the map of the Geological Survey, is 

 either in the Aymestry limestone, or the Ludlow bed. 



One specimen only of another coral, in a very bad state and as 

 yet undetermined, was found associated with the present species. 



The figured specimen of Cyathaxonia Dalmani was obtained from 

 the Upper Silurian of Gothland, and was preserved in the collection 

 of M. Yerneuil ; and I have in my own collection examples from 

 Gothland with which I have compared the Herefordshire specimens, 

 and found them to be identical. 



The figures accompanying this communication represent Hemi- 

 pliyllum Siluriensis, magnified 21 times. Figure 2 shows a horizon- 

 tal section a little below the calice. 



1 Brit. Fos. Cor. pi. 5, p. 279. ^ Hist. Nat. Coral, t. iii, p. 332. 



