282 MR. W. S. KENT ON NEW MADREPORES. [Apr. 4, 



Errina, Gray. 



Millepora (pars), Esper, Pflanzenthiere, t. i. p. 106, 1797. 



Errina, J. E. Gray, Proc. Zool. Soc. p. 85, 1835. 



Non Errina, Pourtales, Bulletin Mus. Comp. Zool. Cambridge, 

 U.S. p. 116, 1867. 



The essential characters of this genus, with its natural affinities 

 not having been very satisfactorily determined, the following, drawn 

 up from the type specimens of E. aspera in the British Museum, is 

 here proposed for its diagnosis. 



Corallum branching, flabellate. Sclerenchyma compact. Surface 

 of the ccenenchyma beset with nariform verrucse, these most abundant 

 towards the distal extremities of the branches. Calices pit-like, 

 circular, for the most part scattered among and concealed by the 

 prominent verrucse. Septal system entirely absent or rudimentary. 

 Columella immersed, stylate, and echinate, almost entirely filling the 

 calicular fossa. 



Errina aspera. 



Millepora aspera, Esper, I, c. Millepora, pi. xviii. figs. 1-4. 



Errina aspera, Gray, I. c. p. 85. 



The characters above given are also diagnostic of the species. To 

 this it may be added that the corallum attains a height and breadth 

 of several inches, is opaque white or cream-coloured, and is met with 

 in both the Mediterranean and northern European seas. 



The ultimate ramifications are terete ; the diameter of the cali- 

 cular fossae about ^ inch. 



The two forms referred to this genus by Pourtales as E. cochleata 

 and glabra evidently belong to a distinct genus, as must also be said 

 of the examples referred to it and described as E. aspera (Gray) by 

 the same writer, contained in the Museum of Comparative Zoology, 

 Cambridge, U. S. Count de Pourtales at once recognized this on 

 my showing him the typical specimens ; and a modified description 

 of his new species will shortly appear. 



Errina proper, on account of its compact sclerenchyma and the 

 form of its columella, is clearly referable to the group of the Stylas- 

 teracese, while in its irregular gemmation it most nearly approaches 

 the genus Allopora. Connected with this mode of increase, how- 

 ever, there is a feature not observable in the last-named genus : 

 instead of being simply terminal, gemmation also frequently occurs 

 on the older portions of the corallum, young calices making their 

 appearance on the surface of the out-growing ccenenchyma. 



The rudimentary condition, or it may be said the entire absence 

 of any recognizable septal system or intermesenteric calcifications, is 

 the full development of a feature observed as exceptional in describing 

 Allopora explanata. The very minute size of the calices at once 

 suggests that septal elements would be of but little service in the 

 economy of the individual polypes. 



The prominent nariform and almost tubular verrucas have, as is 

 not to be wondered at, been mistaken by early writers for the orifices 



