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



cylindrical intervals between them covering each other more or less rectangularly. 

 Skeleton spicules of three forms, viz., (1) small sexradiate, arms not inflated at their 

 junction, alternately pointed, and thickly spined throughout ; (2) much larger se.x- 

 radiate, the same but with the arms slighted inflated at the extremity; (3) still much 

 larger, unispined, but uneven on the surface, and here and there microspined. Flesh - 

 .spicules of two forms, viz., (1) rosette globular, consisting of six short arms, each of 

 wliich is surmounted by five long capitate rays expanded in a vasiform manner ; (2) 

 bundles of minute hair-like undulating acerates like the tricurvate or low spicule." 



" The small sexradiate," Carter continues, " become the centres respectively of the 

 trapezoids, which are thus formed by the extension of a thread of vitreous sarcode, from 

 one end of each of the arms of the sexradiate spicules to the other, strengthened at eacli 

 attachment by subsiding threads and the arm of each end of the latter ; finally increasing 

 in thickness throughout till the trapezoid is fully formed and presents four sides, 

 with eight lantern-like holes in them, one in each triangular face, through which the sex- 

 radiate form of the original spicule may be seen in the centre intact. Spicules 2 and 

 3 form the fringe round the apertures which interknits with the body structure of the 

 lamina internally, the latter or the supposed acerate form extending beyond the former, 

 ])otli distally and proximally, while the flesh-spicules are scattered throughout the 

 structure unequally, that is much more numerously towards the surface." 



Although Carter clearly recognised the essential difi"erence between Myliusia callo- 

 cyathus, Gray, and Myliusia grayi, Bowerbank, their generic separation appeared to 

 him unnecessary, perhaps because of the agreement in the " convoluted cerebriform 

 appearance." He included both in the same genus Myliusia. Carter, however, called atten- 

 tion to the fact that although the skeletal structure of Myliusia grayi agrees very closely 

 with that of many fossil Hexactinellids, such as Scyphia, Ventriculites, Cceloptychium, 

 &c., yet " the general structure of Myliusia grayi, although convoluted, is massive and 

 labyrinthic throughout, not cup-shaped or lioUow in the axis, as that of Ventriculites, 

 while Cceloptychium consists of radiating tubes, more or less branches round a hollow 

 axis or stem, which in the horizontal section resembles Ventrictdites." 



On the other hand, SoUas described in the same volume of the Annals in 1877 a new 

 fossil genus Stauronema, and assigned Myliusia grayi to the Ventriculitidse, which are 

 characterised by a " skeletal network having the nodes complicated by the presence of 

 an octahedral lantern about each one." 



In 1878 Marshall and Meyer' described a Hexactinellid from the Philippines closely 

 related to, yet specifically distinct from, Myliusia grayi, Bowerbank. This they named 

 Myliusia zittelii. 



Of the three specimens examined, the best preserved exhibits a system of meandering 

 folded funnels which have fused with one another, besides wider tubes with walls sup- 



' Mittheil. d. Zool. Museum, Dresden. 



