EEPORT ON THE HEXACTINELLIDA. 339 



lapping of their horizontal rays the squares of the skin. The outermost tip of the 

 exterior ray frequently bears the small rosette above described. 



The most important peculiarities of the new form have been summarised by Murie in 

 the following brief diagnosis; — " Hexaetinellid sponge characterised by its dendritic or 

 shrubby contour, occasionally attaining a height of 3 feet or possibly more. Branches 

 forking or dichotomous, with continuous whorled series of spicular tufts from base to 

 apices. Skeleton only known ; basework composed of relatively stoutish glassy fibres 

 of coalesced sexradiate and spinomucronate spicula, disposed in tolerably compact tra- 

 beculse. Main direction of fibre longitudinal to axis in parallel, straightish, or slightly 

 bent lines, where continued into exterior whorls ; in crossing fibres more irregular, as are 

 the very numerous excretory canals. Oscula and pores of moderate size distributed all 

 over the free surfaces. Flesh-spicula abundant, and of scopuline, acerate, and rosette 

 shapes. A dermal veil of slender interwoven Hexaetinellid spicula probably clothes the 

 major portion, or possibly the entire sponge." 



In a postscript Murie finally calls attention to the fact that his Dendrospongia steerei 

 may be identical with the Sclerotliamnus clausii, Marshall, described a year before by 

 Marshall,' so that the latter name must be accepted as the earlier. 



To the memoir by Murie, Carter has added an appendix in which he expresses the 

 opinion that the fragment from the basal tuft of Euplectella cucumer, which was at first 

 referred by Bowerbank to Farrea occa, and later by Carter to Farrea densa as distinct 

 from Farrea occa, and which was found to be rich in " scopuline spicules," is most pro- 

 bably to be referred to Sclerotliamnus claiisii. 



Sclerothamnus clausii, Marshall (PL XCVIIL). 



Of this remarkable bushy branched species, which difters essentially in external 

 appearance from all known Hexactinellida, only two skeletal fragments belonging to a 

 dead specimen were trawled by the Challenger Expedition in the neighbourhood of 

 Timor (Station 194a, lat. 4° 31' 0" S., long. 129° 57' 20" E.), from a depth of 360 fathoms 

 on volcanic mud. These are small, irregularly rounded, somewhat bent, and slightly 

 knee-shaped branches of the thickness of one's finger, and from 12 to 15 cm. in length. 

 The outer portion has been destroyed by abrasion or otherwise. The tolerably compact 

 fibrous framework exhibits, in longitudinal section, strands of fibres for the most part 

 longitudinally directed, or arched towards the exterior, and laterally curved. They 

 terminate freely on the outer surface, while between them other fibres extend approxi- 

 mately at right angles. The entii-e disposition of the dictyonal framework, and especi- 

 ally the above-mentioned direction of the fibres, corresponds exactly wdth the structure of 

 the framework described by Murie, and represented in a figure which has been copied here 



^Zeitschr.f. wiss. ZooL, BJ. xxv., Suppl. 



