REPORT ON THE HEXACTINELLIDA. 81 



greatly prolonged proximal rays, and distal rays which raise the dermal membrane into 

 pointed elevations, and bear on their extremities somewhat freely projecting floricomes. 



Bundles of very fine raphide-like spicules, which lie close upon the outer ray of the 

 hypodermalia, appear to me to occur here in greater abundance than in Euplectella 

 aspergillum. 



The gastralia are slender penta.cts with prolonged distal rays, while then- atrophied 

 sixth ray often appears as a rounded, more or less projecting tubercle. 



The composition of the much arched sieve-plate does not differ essentially from that 

 of Euplectella aspergillum. In the basal root-tuft I found anchor-like structures 

 similar to those of the latter species. 



Among the Japanese Hexactinellida of Dr. Doderlein there occurs — in addition to 

 the specimen of Euplectella oiveni upon which the foregoing description is founded — 

 a completely macerated and much injured, though coherent tubular skeleton, which may 

 also with probability be referred to Eup)lectella oweni. This forms a tube of 32 cm. in 

 length, somewhat compressed on one side. At the (3 to 5 cm.) wide extremity, the 

 spicules seem loose, but they are fused below into a firm lattice-work. Since not only 

 the position and arrangement of the bands of fibres, but also the structure of all the 

 larger and smaller spicules which I was able to isolate by tapping, fuUy agree with those 

 of Euplectella oiveni, I do not doubt that this specimen is simply a very large and old 

 fragment of Eup)lectella oweni, in which the usually unfused spicules have at a later stage 

 become soldered together. 



6. Euplectella crassistellata, n. sp. (PL XIII. figs. 5-7). 



In the middle of the Pacific (Station 274, lat. 7° 25' S., long. 152° 15' W., depth 

 2750 fathoms, bottom Radiolarian ooze) there were found some plate-like fragments 

 from 4 to 6 cm. square, and about 1 mm. thick, along with a narrow tuft of siliceous 

 spicules 6 cm. long, to which a small part of the plate-like mass was still firmly attached. 

 Round or oval apertures from 1 to 1"5 mm. in diameter occur here and there on the plate. 



I must regard these fragments as a new species of Euplectella, although many 

 characters of this genus are not definitely indicated on account of the insuflicient 

 preservation of the fragments. 



The principal spicules of the plate are represented by diacts which run out to a 

 point at both ends, and are usually provided with a node-like thickening in the middle. 

 These lie scattered without any recognisable regularity of arrangement, somewhat near 

 the inner surface, and parallel to it. 



Besides these and some long thin diact comitalia which are applied closely to the thick 

 principalia, only a few extended spicules are to be found in the parenchyma. Rosettes, 

 however, and a peculiar form of oxyhexaster occur in surprising abundance. These oxy- 



(ZOOL. CHALL. EXP. — PART LIU. — 188G.) Gfgg 11 



