﻿108 MADREPOEAEIA. 



ence of texture is very marked where the open spongy reticulum is growing rapidly and 

 submerging the papiUre. In sections the submerged papillre can be distinguished from the 

 rest of the reticulum by the fan-like arrangement of theii' elements. The papillas reach their 

 full height (2-2*5 mm. high to 1'5 mm. thick) about 1 cm. froih the growing edge. Nearer 

 the growing edge they diminish in height and seem to sink into the slight radial ridges which 

 marlv the border, while proximally to this zone they are progressively submerged by the 

 thickening layer, persisting only in raised patches. Tliere are no papillae on the under surface, 

 which is a smootli reticulum finely ecliinulate at its creeping edges. 



This papillate coral stands quite alone in the collection. It differs from M. papillosa 

 in its larger and more regularly cylindrical papilla?, in this respect approaching Af. vemwosa. 

 It differs from this latter, however, in the apparent independence of the papillse of the calicle ; 

 they are sometimes larger and sometimes smaller, and seldom exactly fill an interstitial space. 



The true character of the under surface is not easy to make out. There appears to be no 

 epitheca following the free expanding edges ; but the naked under surface appears to die 

 down and then becomes grown over again both from the edge, and from scattered centres which 

 perhaps resist the deleterious influence which has destroyed the greater part of the under 

 surface. 



a. Thursday Island. Coll. Saville-Kent. 



82. Montipora mammifera. (PI. XXXIII. fig. 13.) 



Description. — Corallimi small, horizontal, encrusting, thin, under 1 mm. thick at the growing 

 edge, about 2 mm. in the tliicker parts. 



Calicles very minute, 0*25 mm., irregularly distributed, averaging about 1 mm. apart, 

 conspicuously star-like. One, two, three or more primaries are generally distinct and even 

 exsert ; the secondaries are, when present, little more than granulations or echinulse at the 

 margin of the aperture ; fossa conspicuous. 



CcBuenchyma a comparatively speaking coarse reticulum which streams outwards towards 

 the growing edge. In the older parts this forms a thick solid layer on the epitheca, while 

 dorsally the layer also becomes very compact, the vertical threads being thick and trabeculate. 

 On the surface these end as fine echinulations which, seen from above, appear powdery or 

 granular, but seen sideways show as true echinulfe. Papillae are of all sizes, and under the 

 pocket glass highly ecliinulate, rising up over all the older parts of the corallum, from quite 

 minute bushy surgings up of the reticulum to symmetrical nipple-shaped processes 1 mm. high 

 by 1 mm. in diameter. 



There are two small specimens closely encrusting lumps of coral debris. This, in the 

 case of the smaller specimen, seems to be largely composed of a solid mass of Porites, with a 

 regular trabecular structure and appearing at first sight as if it might belong to the Monti- 

 pore. The reticulum of this latter, however, nowhere shows the regular trabecular character of 

 the underlying mass ; nor, on the other hand, do the regularly parallel trabeculse of the Porites 



