﻿172 MADREPORARIA. 



The whole stock has a vertical thickness of about 5 '5 cm., of wMch the upper 4 cm. are 

 living, while in the lower 1"5 cm. tlie stems are dead and corroded, each stem dying 

 progressively upwards. 



The calicles are conspicuous and open, markedly protuberant, the apertures being 

 tilted slightly forwards in the direction of growth ; the margin of the aperture often 

 formed by one or more rings of bhint points, which represent the tips of the trabeculfB 

 from wlricli the septa project. Diameter of aperture 0*75 mm. Laminate radial structures 

 of the protuberant calicles may be obscured, but generally traceable. The septa are incon- 

 spicuous and irregular, in two cycles, the primaries are very short, with two directives in 

 the line of growth often visible down in the fossa. Fossa open and deep. 



The coenenchyma is differentiated into a delicate open axial reticulum composed of 

 longitudinal lamin;^; and a thiu cortical layer, which is dense as compared with the axial 

 strand, but is open and porous as compared with the cortical layer in A./orbesi. Seen from 

 the surface, this layer appears to be a reticulum, densely covered with short blunt echinulffi, 

 which give it a light fragile appearance ; the tips of the branches are whoUy composed of 

 the axial streaming layer, the laminate elements of which run out as short, blunt, free ends, 

 when seen against the light with a pocket lens. 



The type specimen is from Bands. It is a close tangle so that individual stems are soon 

 lost in the repeated fusings ; the stock has been bleached. In addition, there are some un- 

 bleached (red-brown) specimens from Evans Bank, Arafura Sea. These consist of a fragment 

 — which appears to have been secondarily thickened because its dead base is thin like the type 

 — and of three fragments which are clearly specifically identical with the Banda specimen. 

 The thicker fragment departs somewhat from the type in the greater protrusion of the calicles, 

 and in the greater length of the echinulte. Further, the radial arrangement of the elements 

 forming the protuberant margins of the calicles is clearly marked. These calicles strongly 

 recall those of a Turbinarian.* 



a. Banda (with a fragment). H.M.S. ' Challenger.' (Type.) 



I. (Four pieces) Evans Bank, Arafura Sea, H.M.S. ' Penguin.' 



12 fathoms. 



There is also what appears to be a young specimen of this species. It consists of a 

 single short stem with two divergent prongs, each of which divides again quite irregularly. 

 The specimen appears not to have thickened much, it is only from 3 to 4 mm. thick, and, 

 there being hardly any cortical layer developed, the streaming of the axial strand is seen 

 at the surface and gives a character to the surface reticulum. The calicles are not very 

 protuberant and are smaller, but the tendency of the elements on the lower side of the calyx 

 to arrange themselves radially is quite apparent. Owing to the thinness of the protuberant 

 wall, the primaries form external costse as well as internal septa. 



c. (Young stock ?) Evans Bank, Arafura Sea, H.M.S. ' Penguin.' 



12 fathoms. 



* See Ann. and Mag. Nat. Hist., xx. (1897) pi. xi. fig. 5. 



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