240 THE VOYAGE OF H.M.S. CHALLENGER. 



Skeleton. — {a) Dermal; varying much in its degree of development at diflferent parts 

 of the surface. Typically a more or less closely matted, irregular feltwork of slender 

 strongylote spicules, much smaller than the spicules of the main skeleton, {h) Main ; 

 also varying much in its degree of compactness ; a more or less definite reticulation of 

 large sj)icules, with fibres three or four spicules broad, distinct in parts ; sometimes 

 primary fibres, running towards the surface, can be distinguished from the remainder. 



Spicules. — (a) Megasclera ; (1) long, smooth, more or less curved oxea (PI. XXIX. 

 fig. 3), very variable at the ends, sometimes gradually and sharply pointed, sometimes 

 blunted at each end ; ends often rather irregular ; size about 0'9 by 0"025 mm., forming 

 the main skeleton. (2) Smooth, rather slender, very slightly curved strongyla (PI. XXIX. 

 fig. 3a), rounded ofi" at each end, measuring about 0'48 by 0"012 mm., occurring chiefly 

 in the dermal skeleton. (6) Microsclera ; very small, slender diseastra (PI. XXIX. 

 fig. 3&) resembling the typical " chess-man " spicules of Latruncnlia, but not nearly so 

 weU developed. Consisting each of a slender shaft, straight or slightly crooked, some- 

 times rather expanded at the base, not distinctly spined but (commonly at any rate) with 

 a roughened appearance ; bearing two saucer-like whorls, a smaller one close to the base 

 and a larger one some distance above it. There are never any indications of more whorls. 

 The smaller one is slightly concave upwards and the larger slightly concave downwards. 

 The margin of each whorl is normally slightly notched all round. The slender shaft is 

 produced for some distance beyond the upj^er whorl, but instead of tapering ofi' to a point 

 it ends abruptly and is often of the same thickness along its entire course. Length of 

 spicule about 0"037 mm. Diameter of larger whorl about 0'0125 mm. These spicules 

 are abundantly scattered through the dermal membrane and are also found occasionally 

 in the subjacent parts. 



It is extremely unfortunate that the single specimen of this very interesting and 

 important species should be in such poor condition, and also that the locality should Ite 

 uncertain. The label on the bottle bears the inscription "No. 135 ? Date. Oct. 1873. 

 Lat. Long. . Depth, 60 fm's." 



The species is at once distinguished from any of the three preceding by its spiculation 

 (oxea instead of styli), and by the absence of mammiform processes on the surface. 

 Indeed, as we have already pointed out, it is very doubtful whether it even belongs to 

 the same genus. It is distinguished from Mr. Carter's two species, Latrunculia covticata^ 

 and Latruncnlia purpurea,^ which also have oxeote megasclera, by the form of the 

 discaster, which in our species approaches that of a typical Latruncnlia much more nearly 

 than in either of Mr. Carter's. This forms an argument for including all in the same 

 genus, but it is a very slight one when compared with the arguments against this 

 view. As, however, we have only a single specimen we leave it where it is for the 

 present. 



' Loc. cit. su-pra. 



