1870.] On the ' Porcupine '-Expedition Madrcporaria. 289 



March 24, 1870. 



Lieut-General Sir EDWARD SABINE, K.C.B., President, in 



the Chair. 



The following communication was read : — 



cc On the Madrcporaria dredged up in the Expedition of H.M.S. 

 f Porcupine/ " By P. Martin Duncan, M.B. Lond., F.E.S., 

 Sec. Geol. Soc, Professor of Geology in King's College, Lon- 

 don. Received February 26, 1870. 



Professor Wyville Thomson, Dr. Carpenter, and Mr. Gwyn Jeffreys have 

 placed the collection of stony corals dredged up by them in the ' Porcupine' 

 Expedition in my hands for determination. They have kindly afforded 

 me all the information I required concerning the localities, depths, and 

 temperatures in which the specimens were found. 



My report has been rendered rather more elaborate than I had intended, 

 in consequence of the great consideration of Professor A. Agassiz and 

 Count de Pourtales in forwarding me their reports* and specimens rela- 

 ting to the deep sea-dredging off Florida and the Havana. 



They have enabled me to offer a comparison between the British and 

 American species, which I had not hoped to do before the publication of 

 this communication. 



Contents. 



I. List of the species, localities, depths, temperatures. 

 II. Critical notice of the species. 

 III. Special and general conclusions. 



I. Twelve species of Madreporaria were dredged up, and the majority 

 came from midway between Cape Wrath and the Faroe Islands. Others 

 were also found off the west coast of Ireland. Many varieties of the species 

 were also obtained, and some forms which hitherto have been considered 

 specifically distinct from others, but which now cease to be so f. [See Table, 

 p. 290.] 



List of species known only on the area dredged, or in the neighbour- 

 ing seas. 



1. Amphihelia atlantica, nobis. 



2. ornata, nobis. 



3. Allopora oculina, Ehrenberg. 



* Contributions to the Fauna of the Gulf-stream at great depths, by L. F. de Pourtales, 

 1st & 2nd series, 1868. Bull. Mus. Comp. Zool. Harvard College, Cambridge, Mass., 

 Nos. 6 & 7. 



t One specimen came from the 'Lightning'' Expedition. It must be remembered 

 that all th deep-sea corals known to British naturalists were not dredged up. The 

 Htylaster rosea, for instance, was not amongst the collection. 



VOL. XVIII. Z 



