﻿TUBERCULATE MONTIPOE^. 143 



120. Montipora amplectens. (PI, XXXIV. fig. 8.) 



Description. — Corallum encrusts large stones as a thin sheet 2 to 3 mm. thick, creeping 

 round up the sides and meeting over the top, in close contact, and covering over other 

 encrusting organisms. 



Calicles numerous and crowded at irregular distances, about • 75 mm. diameter, conspi- 

 cuous, with rather regular, almost laminate primaries not reaching to the half radius circle, 

 secondaries only irregularly and partially developed. Where the coraUum encrusts the under 

 sides of the stone the calicles are much further apart and more regular, and have thicker, 

 more regula septa. 



Coenenchyma shows in sections of the portions creeping up the sides of the stone a well 

 developed, open, reticular streaming layer resting upon the epitheca ; this rises, from 2 to 3 cm. 

 from the growing edges, into small, thin, feathery plates and ridges, which form a kind of 

 irregular network, with the calicles in the meshes. These plates gradually change into tubercles, 

 which are thickly crowded, very irregular in height, and so finely feathery that the surface of 

 the corallum looks as if covered with small balls of wool ; the tubercles do not rise immediately 

 round the margins of the calicles, and are very seldom arranged in rings. Groups here and 

 there, in irregular association with one or more calicles, fuse and rise into small knobs or 

 crests hardly 2 mm. high. The section of the lower portion of the corallum shows (1) a solid 

 layer nearly 1 mm. thick resting upon the epitheca ; (2) a very thin vestige of the streaming 

 layer; and (3) an almost solid layer of thick trabeculse. The tubercles hardly rise above 

 the surface, but -are compact and crowded and make the surface almost solid, the distances 

 between the calicles being much greater. 



There is only one specimen of this coral. It completely envelops the pointed end of a 

 nearly fusiform piece of rock. There are no indications of any previous growths. The method 

 of growth is peculiar, the corallum growing upon the sides and bending smoothly round over 

 on to the uppermost surface, covering the stone with a thin, closely fitting single layer of 

 corallum. More specimens, of course, are needed to ascertain for certain whether this is 

 typical or merely accidental. 



The thin streaming layer between two nearly solid layers, as seen in the section of the 

 lower parts of the corallum, recall the condition in M. bilaminaia, only in that case the 

 corallum was thin and explanate, and the density was needed for strength ; in the present case 

 the lower parts of the corallum show the same tendency to solidify which has already been 

 frequently noticed and assumed to be due to the downward streaming of fluids under the 

 action of gravitation, 



a. China, probably south (with Chinese Commissioners, Fisheries] 



Madrepore ? sp.). Exhibition, 1883. ] (^JV^-) 



