196 



Prof. S. J. Hickson. On Ceratopora, the [June 15, 



in Heliopora led to the erroneous conclusion that Heliopora was a 

 .Zoantharian coral, and the presence of tabuke in Millepora led to the 

 classification of the Milleporidse with other tabulate corals. It was not 

 until Moseley examined the soft parts of Heliopora, and until Agassiz 

 examined the soft parts of Millepora, that these corals were assigned to 

 their proper position in the animal kingdom. 



However, in the absence of soft parts to assist him, the palaeontologist is 

 obliged to base his classification on the skeletal structures, and consequently 

 any new light that can be thrown on the structure and formation of the 

 calcareous tubes of recent corals may be of considerable importance in his 

 attempt to create a natural classification of the extinct forms. 



The examination of an interesting dried coral obtained by the naturalists 

 of the American steamer " Blake " has brought to light certain features which 

 are, I believe, unique among tubular corals, and I have ventured to describe 

 them in a separate paper, in the hope that they may be of service in solving 

 some of the difficult problems of the fossil corals. 



The single specimen of the species which I propose to call Ceratopora 

 nicholsonii was obtained at the " Blake " Station 22, off Cuba, in 100 fathoms 

 of water. Whether it was alive or not at the time of its capture I cannot 

 say, but it was not preserved in spirit, and consequently nothing remains of 

 its soft parts. It is undoubtedly the same species, if it is not actually the same 

 specimen, as that figured by Agassiz in " The Three Cruises of the ' Blake,' " 

 vol. ii, p. 83, but the only passage in the text that refers to it is as follows : 

 " A supposed Pavosites is probably a bryozoan genus, growing in the shape of 

 a mushroom, and allied to Heteropora." 



The specimen was forwarded to me for examination by Prof. Stanley 

 Gardiner, together with some interesting letters from the late Prof. Alleyne 

 Nicholson, addressed to Sir John Murray, on the subject of its structure. 



The specimen consists of a lump of very hard crystalline limestone 

 perforated in various directions by boring sponges, and projecting from the 

 irregular mass of the lump there is a mushroom-shaped process (fig. 1, Plate 6) 

 capped by a thin brown lamina, nearly circular in outline and 42 mm. in 

 diameter, composed of small short vertical tubes. Without going into details, 

 it may be stated that there can be little doubt that the whole lump of coral 

 was formed by the successive growth of the organisms that formed the brown 

 tubes of the cap, notwithstanding the fact that sections of the main substance 

 of the specimen show no trace of tubular structure. 



Before describing my own observations on the structure of the brown 

 tubes, I may remark that Nicholson, in his letters to Sir John Murray, 

 pointed out that the specimen differs from Heteropora in the absence of 



