108 MAEINE 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 0"018 mm., 



0-108 X 03 mm. 



(b) Short broad spindles with tubercles at each end and in two whorls 



between, e.g. 0"0-4x0025 mm. 



(c) Fusiform types intermediate between (a) and {U) with sharper 



tubercles . 

 d) A few non-foliate clubs, e.g. 0'05o x 0'028 mm. across tlie 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. 0096 x0'012 mm. 



The generic distinctions of the Melitodidje 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 <fc 4.) 



See Gray : Proc. Zocil. Soc. London, 1859, p. 486 ; Catalogue of Litliopliytes in the 



Bi-itish Museum, 1870, p. 11, 1 fig. 

 = Mopsea bicolor, KiJlliker, Icoiies Histologicfe, p. 142, 1 fig. 



It is interesting to find in this collection the peculiar Melitodids to which 

 Grixy gave the names Clathraria ridtrinodis 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. ruhrinodis, is represented by a spiecimen about 

 12 cm. 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. Tliis 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 

 ess marked tendency to dichotomy, and some of them narrow towards the 



* The account of Clathraria ruhnnodu and C. acuta was prepared by Miss Doris L. 

 SJacltinnon as part of a thesis for the degree of B.Sc. in the University of Aberdeen. 



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