﻿142 MADREPORARIA, 



texture, and the lower surface very irregular, due to protrusions of living coral encrusting 

 masses of worm-tubes and Balanids. The epitheca is developed in patches but is soon 

 corroded. 



Calicles densely crowded in the broad valleys, more sparse on the eminences, average 

 1 mm. Two cycles of fine, very distinct septa, reacliing to about the half radius circle ; direc- 

 tives here and there pronounced. The more crowded calicles are separated from one another 

 by tliin partitions of a fine spiky reticulum ; here and there a stray tubercle, short and stout, 

 manages to rise up between. On the eminences the calicles are often carried up by encircling 

 groups of tubercles. Where the corallum is beginning to die down, the reticulum, including 

 septa, becomes denser, tending to close and diminish the size of the polyp cavities, and thus 

 also increase their distances apart. The calicles on the under surface show the same variation, 

 but they are never so densely crowded as on the iipper surface. 



Coenenchyma. The laminate reticular layer, appearing at the surface of the growing edge, 

 forms a finely striated border, the striae being the thin ccenenchymatous laminse standing up 

 edgewise and parallel with one another (cf. M. striata, M. aiistraliensis, from the same locality). 

 A short distance from the edge this layer becomes almost solid, and on it rests a thick but 

 very irregularly developed trabecular layer. In the smooth valleys crowded with calicles tlie 

 trabeculas are distinct but not very thick, but on the eminences they may attain to an enormous 

 size, being occasionally a millimetre in thickness. These trabecule rise very irregularly above 

 the surface, forming conspicuous tubercles of all sizes and shapes, cylindrical, flattened, triradiate, 

 but all alike round-topped, swollen, bushy but compact, and with clear outlines. They are 

 arranged at all angles ■with one another and show no definable association with calicles, 

 round which, however, by fusing together in twos and threes to form plates, they make tall 

 but discontinuous ramparts. When the tubercles are very crowded and fused together, they 

 tend to produce the proliferation of the surface which characterises M. prolifera. Where the 

 surface is dying down the trabeculse thicken and their tips become smooth and flat and all on 

 the same level ; the gradual filling up of the spaces between soon makes the corallum a solid 

 mass. 



Tubercles also appear on the under surface, each tubercle being" distinct, deep openings 

 into the coenenchyma being visible between them. Elsewhere the under surface is formed by 

 the trabeculae all ending in distinct flat but frosted grains. 



There is only one specimen of this beautiful coral. It is more than 20 cm. deep, and 

 though only 1 ' 5 cm. thick stands 5 cm. high, owing to the undergrowth mentioned above. 

 Both surfaces are beset with Balanids, all of which are grown over, their apertures, however, 

 remaining open. The specimen is peculiar on account of the size and variety of its tubercles 

 with their solid trabeculfe and cores. Here and there where the rich red-brown granulation 

 or frosting which coats the tubercles has been rubbed off, the tubercles stand up Kke groups 

 of opaque solid crystals. 



a. Houtman's Abrolhos, West Australia. CoU. Saville-Kent. (Type.) 



