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



gentle elevations and depressions, which may be, however, the results of desiccation. 

 The inner surface of the wall of the cup exhibits here and tliere inconspicuous, ridge-like 

 elevations with a thin edge. 



The extremely delicate dermal membrane, which forms a fine lattice-work is pre- 

 served onl}- in a few sheltered portions. The parenchymal skeleton is represented 

 by a feltwork of spicules, which are disposed in strands 2 to 4 mm. broad, and 

 enclosing roundish spaces of various sizes. The gastral skin, which also forms an extremely 

 delicate and fine network, exhibits a feltwork of spiculav sti'ands with meshes somewhat 

 narrower than those in the dermal skeleton. 



The subsequent influence of damp has caused this specimen to fall in, so tliat the two 

 halves of the wall of the cup have been united. I was therefore unable to discover any- 

 thing definite as to the nature of the inner surface or of the oscular margin. Dr. Doderlein 

 told me, however, that this specimen, even when still well preserved, " exhibited a marked 

 lateral compression. The inner wall or cup exhibited ridged elevations. The free upper 

 margin had no marked plaiting, and ended in a slender smooth edge without a fringe of 

 spicules. At the base of the cup the larger apertures of the efferent canals were apparent." 



A second smaller sj)ecimen of this species, measuring 13 cm. in height and 8 in 

 breadth, agrees closely with the above. It also exhibits a laterally compressed cup-like 

 or saccular shape, with a thin oscular margin, but is attached to the firm substratum at 

 several places, over a comparatively broad expansion. Two roundish apertures, 4 mm. 

 in diameter, occur near the lower end. 



The principal portion of the parenchymal skeleton consists of long slender diacts, 

 occurring either isolated or disposed in strands. They exhibit a central nodal thickening, 

 and the rough ends are sometimes conically pointed, sometimes simply rounded, and 

 occasionally thickened in a club-shaped fashion. Between these there is a scattered 

 occurrence of the familiar oxyhexasters, in which the principal rays are very short, and 

 frequently almost aborted, while long terminal rays, present in variable number, are 

 somewhat curved at their base, but otherwise quite straight on to the pointed outer end. 

 Oxyhexacts occasionally occur in which the rays are twisted at a point corresponding to 

 that at which the terminal rays arise from the principals in the oxyhexasters. They 

 are doubtless degenerate oxyhexasters, which are again almost reduced to simple oxy- 

 hexacts, retaining only a trace of their metamorphosis in the twisting at the base. 



In certain regions, especially in the subdermal trabecular spaces, there is an abundant 

 occurrence of large rosettes with terminal rays bearing terminal discs. These spicules 

 but rarely exhibit the ty^^ical number of principal rays, but as a rule eight are present. 

 When only six principals are present, as in the form represented in PL LXIV. fig. 7, 

 they intersect as usual at right angles in a somewhat thickened node, and are rather 

 thick and cylindrical. At the slightly expanded outer end they divide into three to six 

 straight or somewhat S -shaped terminals, which diverge slightly in a tuft, and attain a 



