﻿92 MADREPORAEIA. 



and crowded, and between the ridges are numbers of cylindrical calicles squeezed in 

 between them. The deep vertical ridges in this type may help to strengthen the thin 

 corallum. 



a. (In three pieces) Macclesfield Bank, H.M.S. ' Eambler.' (Type.) 

 20 fathoms. 

 h, c. (Young specimens), 13 fathoms. „ „ 



d. (Young specimen), 20 fathoms. „ „ 



Another specimen, apparently a fragment of a very large frond, from the same locality, 

 showing the same development of tall thin plates of uniform thickness and forming parts of 

 longitudinal series, with the same general method of growth and very nearly the same texture 

 of the ccenenchyma, must also, on these counts, be classed here. This specimen was also 

 labelled M. prolifcra by Mr. Bassett-Smith. The remarkable differences may, perhaps, be 

 referred to the age and thickness of the frond. The ridges tend to be broken up into tail thin 

 papillse, slightly swollen and twisted at their tips ; the corallum, exclusive of the papillae, is 

 nearly 5 mm. thick as against about 2 • 5 mm. in specimen a ; the tendency to raise the 

 caUcles above the surface is only just traceable, while the calicles themselves are much 

 larger, being nearly 1 mm. across. They are also deep and conspicuous and with primaries 

 reaching across the half radius circle (one septum often specially developed as a directive), 

 and six minute and irregular secondaries. I place this specimen with the rest because it 

 is possible that the development of the upper thickening layer would bring about these 

 changes, the calicles would grow, and the lower continuous portions of the longitudinal ridges 

 be submerged. The surface between the papUlffi is everywhere concavely depressed and smooth, 

 being composed of a flaky reticulum, the flakes lying mostly in the horizontal plane. There 

 are no pendent knobs on the under surface. 



e. Macclesfield Bank, 26^ fathoms. H.M.S. ' Eambler.' 



A distorted encrusting fragment, with no definite character on the upper surface, but with 

 indications of papillse such as are shown on the last specimen, may belong here. This and 

 the next are remarkable for the great depths at which they appear to Uve. 



/. Macclesfield Bank, China Seas, Coll. Bassett-Smith. 



27-40 fathoms. 



Another specimen, disfigured by Balanids, but apparently belonging here. 

 g. Macclesfield Bank, 30-44 fathoms. Coll. Bassett-Smith. 



The last specimen, while it apparently belongs here, is remarkable because it appears 

 to be a transition form between this type and the tuberculate species, M. minuta. It differs 

 from the type chiefly in the tendency to produce tubercles round the growing edge ; the ridges 

 are like those of the type, but a Little way from the edge the whole surface between the ridges 

 becomes tuberculate. The ridges are much lower and more continuous, tending, however, to 

 break up into series of tubercles. The tubercles themselves are usually very small, seldom 

 rising as high as the ridges. Here and there the ridges may be mere papillse ; while these 



