﻿122 MADEEPOEARIA. 



the epitheca, except where the edge is or has been reflexed, in which places a trabecular layer 

 consisting of long thin threads runs down to the epitheca. Above the streaming layer there 

 is an irregular trabecular layer, consisting here of short stout trabeculoe, there of fine points. 

 This arrangement shows at the surface as a smooth, very open, thread-like reticuliun, inter- 

 rupted here and there by small irregular groups of feathery tubercles. These tubercles, 

 which are very irregular in size and have no sharp outlines, are generally associated 

 with calicles, but may stand up singly above the open reticulum. The gro ups of tubercles 

 (generally five) which irregularly surround the calicles, never form symmetrical rings, 

 but small mounds rising about 1 mm. high and some 2 mm. in diameter, and scattered 2 to 

 3 mm. apart, and in marked contrast to the intervening spaces of smooth, open, thread-like 

 reticulum. 



The type specimen differs from all other Montipores in the peculiar specialisation of its 

 ccenenchyma. It is an explanate semicircular growth of some 16 cm. radius. The central 

 parts are thin and translucent, arching high and free over dead former growths, by one of 

 wliich it appears to have been laterally attached to the substratum. The section of the corallum, 

 and also the surface of the wrinkled epitheca, show that the growing edge had already been 

 reflexed twice at earlier stages of growth, the new edge in each case subsequently growing out 

 further, and again bending under. The surface is made somewhat irregular by Balanids, 

 many of wliich have been grown over by the coral. 



The specimen was determined as M. cffusa for the ' Challenger ' Eeport, but the specimens 

 now described on p. 144 and figured (Plates XXV. and XXVII.) agree better with Dana's 

 description and figure of that species (Tahiti). 



a. Zamboanga (in three fragments). H.M.S. ' Challenger.' (Type.) 



100. Montipora listeri. (PL XXXIII. fig. 18.) 



Description. — Corallum tliin, explanate, with edges irregularly bent back. New growths 

 develop upon the edges of the old ; 2 mm. thick at margin, increasing to 6 mm. The epitheca 

 from 1 mm. to 1 cm. behind the growing edge. 



Calicles conspicuous, star-shaped, about • 5 mm., cleanly cut out of the thick smooth flakes 

 of the ccenenchyma, close together in irregular concentric rows, which rows, however, may be 

 2 to 3 mm. apart. Parts of two cycles of septa, not reaching to the half radius circle, often 

 irregular but distinct, the directive primaries conspicuous ; fossa open. On the under surface 

 the calicles are larger and more conspicuous, each being surrounded by a prominent ring 

 beset with two cycles of minute septal teeth. 



Ccenenchyma round the growing edges and on the under surface, a loose, thread-like, very 

 open reticidum. This forms a solid layer resting on the epitheca. The streaming layer is coarse 

 and composed of very thick threads, from which stout, nodulated and closely packed trabeculse 

 are developed. These rise above the surface as tubercles, which are feathery and hence have no 

 distinct outlines. They are of two kinds, and the contrast between them lends the coral its 



