68 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
The spicules, which are mostly yellowish, include : — 
(a) Narrow tuberculate spindles of various sizes, e.g. 0°15 x 0018 mm., 
0-108 x 0°03 mm. 
(b) Short broad spindles with tubercles at each end and in two whorls 
between, e.g. 0°04 x 0025 mm. 
(c) Fusiform types intermediate between (a) and () with sharper 
tubercles, 
d) A few non-foliate clubs, e.g. 0°:055 x 0°028 mm. across the head. 
(e) Some pale yellow or almost colourless rods, sometimes almost 
straight and smooth, often with a median prominence on each side, 
often slightly curved at the ends, e.g. 0:096 x 0°012 mm. 
The generic distinctions of the Melitodidze are not very satisfactory, but 
we may note that the absence of foliaceous clubs, the presence of some small 
nodular spicules in the cortex, and the canals in the axis point to Melitodes. 
Locality.—Mersa Abu Hamama, from a muddy bottom, at a depth of 
10 fathoms. 
* CLATHRARIA RUBRINODIS, Gray. (Plate 6. figs. 3 & 4.) 
See Gray: Proc. Zool. Soc. London, 1859, p. 486; Catalogue of Lithophytes in the 
British Museum, 1870, p. 11, 1 fig. 
= Mopsea bicolor, Kolliker, Icones Histologice, p. 142, 1 fig. 
It is interesting to find in this collection the peculiar Melitodids to which 
Gray gave the names Clathraria rubrinodis and C. acuta. It is rather 
remarkable that such striking forms have not been more frequently collected. 
Apart from Gray’s brief descriptions, we have found no reference to 
Clathraria. 
The larger species, C. rubrinodis, is represented by a specimen about 
12 em. in height, which was probably the upper part of a large colony. 
This is suggested by the size of some of the fragments found in the same 
vessel. 
The branching is mainly in one plane, and there is abundant anastomosis. 
The branches arise almost invariably from the nodes. There is a strong 
tendency to dichotomy, and the two branches diverge at a wide angle at their 
common origin. This gives a very characteristic appearance, which is 
increased by the fact that each of the cylindrical branches is of uniform 
width throughout its length, and terminates bluntly, or may, indeed, be 
slightly thicker at the tip than at its origin. The smaller twigs show a much 
less marked tendency to dichotomy, and some of them narrow towards the 
* The account of Clathraria rubrinodis and C. acuta was prepared by Miss Doris L. 
Mackinnon as part of a thesis for the degree of B.Sc. in the University of Aberdeen, 
