﻿PAPILTATE MONTIPOE^. 73 



53. Montipora senigmatica. (PI. VIII. fig. 2 ; PI. XXXII. fig. 18.) 

 Montipora papulosa, Bassett-Smith {non Lamarck), Ann. and Mag. Nat Hist., 6° vi. (1890) p. 450. 



Description. — Corallum explanate, complete form unknown, apparently a large, thin, 

 horizontal plate ; 2 mm. thick at edge, 7 to 8 mm. at 14 cm. from edge, very dense and heavy ; 

 epitheca feebly developed far from growing edge. 



Calicles not easily distinguishable to the naked eye, from • 50 mm. across, star-shaped ; 

 six prominent but irregular septa stretching far beyond the half radius circle, and generally 

 with a few rudimentary secondaries. Fossa and interseptal loculi only distinguishable under 

 a pocket lens by their star-shaped arrangement from the open meshes of the interstitial 

 reticulum. On the under surface, the calicles are smaller, ca. 0*40 mm., and mostly on the 

 summits of small blunt conical processes, or else the aperture with its septa rises like a low 

 disc above the surface. These give the otherwise smooth solid under ^ surface a pimply 

 appearance. 



(Jcenenchyma in section is very dense, the streaming layer being a coarse reticulum. It 

 dips slightly ventrally to form the dense tissue of the under surface, and rises dorsally into a 

 thick dense layer, the reticular threads being very thick. On the upper surface itself, the 

 threads are not yet thickened, and they there form a perfectly level, loose, open filamentous 

 network. The papillce are quite irregular in shape and distribution ; they average 2 mm. 

 diameter and 1 mm. high. No relation between them and the polyp cavities can be made out, 

 although the latter sometimes open low down on the sides of the papillae. Wherever the tips 

 of the papillce, or indeed the surface ccsnenchyma, has been rubbed off, the stout reticulum of 

 the underlying tissue is visible. 



This specimen, which was labelled M. 2}apillosa by Mr. Bassett-Smith, differs from that 

 type as figured by de Blainville in not having the papilla arranged in any longitudinal series 

 — a feature emphasised by Lamarck (see M. papillosa). Indeed, in this coral, the papillce do 

 not appear at all near the growing edge, which is smooth and solid looking. Further, the 

 whole character of growth appears to differ from that of M. piapillosa, the calicles of which 

 are very distinctly shown in de Blainville's drawing, whereas they are hardly visible to the 

 naked eye in this coral. The specimen represents a large, thin, triangular sheet of an old 

 dead frond, across the middle of which a new layer of living coral has spread. There is 

 nothing to show how the frond was originally attached. From its weight and solidity we 

 may conclude that it was a horizontal growth. The dead portion had become very solid and 

 stony. 



■ a. Tizard Bank, China Sea. H.M.S. ' Eambler.' (Type.) 



