﻿174 MADREPORAEIA. 



exact character of the radial structures is usually obscured by the solidification of the 

 ccenenchyma round the margin. Interruptedly laminate septa are here and there conspi- 

 cuous. Parts of two cycles appear ; they are often mere spinelike projections of the surface 

 granules into the aperture. In parts where the surface granulation is specially richly 

 developed, the margin and septa may be so frosted over as almost to close the aperture. 

 Well developed primaries may appear club-shaped, i.e. with round and slightly swollen tips. 



The axial strand of the ccenenchyma is composed of stout lamina; and is rather dense. 

 The sides of the tips of branches, where it comes to the surface, appear furrowed, the furrows 

 running irregularly upwards. The cortical layer is very dense — indeed, on the thicker stems 

 it is solid. The surface is finely frosted over with granules. 



There are three small portions of a stock together with two fragments which originally 

 belonged to larger specimens, from the Solomon Islands, preserved in the Vienna Museum. 

 They approach nearest to Anacropora gracilis, but differ in having thinner stems, being slightly 

 more arborescent, and in the much feebler development of the protuberant calicles, and 

 consequent less marked lamination of their radial structures. 



a. Solomon Islands. Vienna Museum. (Type.) 



h. (In four fragments.) „ 



4. Anacropora reptans. (PI. XXXIV. fig. 19.) 



Description. — Corallum a matted tangle which appears to creep low down along the 

 ground. The thinner stems are about 4 mm., with branches about 3 mm. thick ; the older and 

 thicker stems are from 6 to 7 mm. thick. From the younger, thinner stems the branches 

 shoot out nearly at right angles, while the older portions of the stock, consisting of thicker 

 stems, become closely matted, often complicated by the fusion of fragments accidentally 

 broken off and caught among the branches of the stock. 



The calicles are not tilted in the direction of growth, but look straight out ; they are 

 raised on rounded mammillate swellings which are not conspicuous on the younger, thinner, 

 stems, but, in older and thicker stems, may become nipple-shaped, 1 mm. high and 2 mm. in 

 dianr.eter at the base. The aperture of the polyp-cavity has no distinct margin and no clear 

 fossa, but the protuberances are highly echinulate, and, at the top, six prominent radial septa 

 (frequently laminate) stand up above the rest. These exsert septa are often thicker and stouter 

 than any of the other echinulte round the margin, and one or two are generally specially 

 developed as directives. The septa are often irregularly disposed, but in symmetrical calicles 

 two cycles can be made out, the second being feebly developed. 



The axial streaming layer of the ccenenchyma consists of a loose laminate reticulum, the 

 laminae so full of large round pores as to make the reticulum appear filamentous. The cortical 

 layer is thin and dense, but is perforated by canals ; the sm-face is densely echinulate and 

 has, to the naked eye, a fine and velvety appearance. The echinulse are very thin and delicate 



