﻿22 MADREPOEARIA. 



vertical .dements of the Teticnlam form thin, short, very distinct trabeciJaj. The projecting 

 granules all reach the same level, and are of about the same size, although quite irregular in 

 shape ; having a whitish appearamce, they give a soft velvety sheen to the whole surface. 



The single specimen covers an irregular surface 11 by 7 cm., and appears to differ from 

 M. subtilis chiefly in the greater coarseness, i.e. size, of all its elements. 



a. Macclesfield Bank, China Seas, 44 fathoms. H.M.S. ' Eambler.' (Type.) 



4. Montipora stratiformis. (PI. T. fig. 1 ; PI. XXXI. fig. 4.) 



Description. — ^Corallum explanate, encrusting, 3 to 4 mm. thick, without conspicuous free 

 edges; each new growth closely covers over the preceding, the edges drooping down. An 

 epitheca follows the advancing edge. 



Calicles minute, 0*4 mm., conspicuous as deep black punctures of irregular shapes. 

 Only a few thick primary septa appear round the aperture, the complete cycles, primary and 

 secondary, being seen only lower down, the secondaries much less developed than the primaries. 

 The interseptal loauli are not sharply bounded, but open all round irregularly to the spaces 

 of the coenenchyma; hence, the broken margin of the aperture. The few large primaries 

 appearing round the aperture are simply thick ends of the open surface reticulum. 



The reticular streaming layer of the coenenchyma is well developed and rests ventrally 

 on a solid layer of varying thickness in contact with the epitheca. The upper thickening 

 layer tends to have its vertical elements slightly thickened, but they do not form trabeculse. 

 The free tips of these elements do not appear to project freely above the surface, but on shooting 

 above the levels of the caKcles, they are joined together by horizontal threads. These tlireads, 

 running from point to point and twisting at all angles, give rise here and there to an arabesque 

 pattern. We have thus the thickening corallum -svith a surface layer of loose open reticulum 

 threatening to submerge the polyps, whose full cycles of septa always remain below the 

 irregular aperture. 



There is only one specimen which appears to be perfect. It is a massive block, 3 cm. 

 thick and 6 cm. long, wliich has been built up by successive growths of this same coral ; at 

 least three distinct layers of the same size can be easily distinguished ; below these, the coral 

 is so corroded and tunnelled through by other organisms that it is difficult to recognise. The 

 two lower of the three uppermost layers are thicker than the uppermost, which, as we have 

 seen in the description, was evidently thickening. It appears, then, here as if we have the 

 greater part of the history of a Montiporan stock. The colony, after building up a certain 

 thickness of coenenchyma (which latter, as is typical of the group, grows faster than the 

 polyps lengthen) dies down and a fresh layer of polyps covers it over. 



Not only is the surface covered with young Balanids, but certain organisms (? boring 

 Molluscs) have their tunnels running through the whole series of layers, and have in some 

 way hindered the uppermost living layer from growing across the mouths of their holes. 



a. New Guinea. Vienna Museum. (Type.) 



