﻿GLABROUS MONTIPOK^. 29 



and there, however, the interstices show slight tendencies to surge~upwards (as in spumosa). 

 A few knobs are formed, apparently by such local surgings, but on the whole the surface is 

 smooth and flat. 



There is only a fragment, which I thought it possible at one time to unite with 

 M. explanata, at another with M. exserta, but the differences on close inspection are in each 

 case too great. In making a type of a small fragment, so broken that it gives hardly any 

 indication of the method of growth of the whole, I should expressly state that this arrangement 

 is only provisional. Such a fragment often shows interesting structural features, which 

 deserve separate description, although it is highly probable that the acquisition of a few 

 series of complete stocks would serve to unite many of such separate fragments together. 



a. Albany Passage, Great Barrier Eeef. ColL Saville-Kent. (Type.) 



12. Montipora complanata. 



Poriies complanata, Lamarck, Hist. d. Anim. sans Vert., ii. (1816) p. 272. 



Montipora complanata, Milne-Edwards and Haime, Ann. d. Sci. Nat. (3°) xvi. (1851) p. 59. 



Description. — Corallum explanate (complete form unknown), thin and nearly flat, 2 mm. 

 thick at growing edge, 3 mm. at 6 cm. from the margin ; the epitheca may reach the edge or 

 be tilted back by a thickening of the coeneuchyma. 



CaLicles numerous, conspicuous, nearly equal in size and in distance apart, hardly 

 0*5 mm., seldom sharply defined all round. Six somewhat thickened but unequal primaries, 

 which are mere irregular projections of the thick reticular threads ; directives here and there 

 visible to the naked eye ; often rudimentary secondaries. Only a few caUcles open on the 

 under surface, except where the coenenchyma has thickened and threatened to roll back the 

 epitheca. 



The ccenenchyma shows in section a very coarse but close streaming layer. The upper 

 hickening layer is conspicuous because the vertical elements are almost trabecular, but are 

 not much thicker than the junctions. The upper surface is irregularly and loosely spongy, 

 without any definite features, the threads being coarse. On the under surface, which is fine 

 and compact, the epitheeal film is very thin,, and shows all the tracery and granulations of 

 the reticulum in relief. 



Of the two specimens in the Paris Museum (245a, 2456), the foi-mer is undoubtedly the 

 original Porites complanata of Lamarck, first identified as a Montipore by Milne-Edwards and 

 Haime. In general appearance, the specimen somewhat resembles M. exserta of Quelch (see 

 PI. II. fig. 4), but it difl"ers in the absence of the exsert septa of this latter species. Another 

 probably close ally is M. glabra, see p. 32. This, indeed, may be specifically identical with 

 Lamarck's type; The Paris specimen 2456 is apparently a young leaf of oneof the foliate 



