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



occupies only the upper quarter of the cortex, and that the spicules composing it project 

 beyond the surface for nearly half their length. The lower three quarters of the thick 

 ectosome are penetrated and strengthened only by the ends of the main skeleton fibres. 

 (Compare this arrangement with that found in Suherites caminatus, where the cortical 

 layer of spicules occupies nearly or quite the entire thickness of the ectosome.) 



Spicules. — Megasclera; all tylostylote. (1) Large, stout, straight, gradually and very 

 sharply pointed, with very slightly developed heads, which are a little elongated ; size 

 up to about 1-2 by 0'02 mm. These spicules occur in the fibres of the main skeleton. 

 (2) Much smaller, straight or slightly curved, slender, gradually and sharply pointed, with 

 heads more distinctly marked and usually of the shape termed by Bowerbank "enormi- 

 spinulate," .size variable, say about O'S by 0-006 mm. These spicules form the special 

 cortical skeleton and also occur in bundles or tracts in the deeper parts of the sponge. 



We at first put this species down as a slight variety of Suherites caminatus, nobis, 

 but our subsequent more careful examination of it has proved it to be really quite distinct, 

 although in many respects the two species resemble one another. The most important 

 points of diflerence concern (1) the oscula, which are minute and non-tubular; (2) the 

 arrangement of the cortical skeleton (w'cZe sttpra) ; (3) the form and size of the cortical 

 spicules, which in the present species are much smaller and slenderer than in Suherites 

 caminatus. In minute histological characters, however, the two species come very close 

 to one another. 



iocaZ%.— Station 150, February 2, 1874; lat. 52° 4' S., long. 71° 22' K; between 

 Kerguelen and Heard Islands ; depth, 150 fathoms ; bottom, coarse gravel ; bottom 

 temperature, 35°'2. One specimen. 



Suherites perfectus, Ridley and Dendy (PI. XLI. fig. 9 ; PI. XLV. figs. 3, 3a, Sh). 



1886. Suherites perfectus, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, voL xviii. p. 485. 



Sponge (PI. XLI. fig. 9) erect, lobose. The single specimen in the collection is a 

 simple, upright, subcylindrical lobe, 81 mm. high by about 19 mm. in diameter. 

 Colour in spirit brownish-yellow. Texture hard, firm, very slightly compressible. 

 Surface minutely reticulate, almost glabrous in appearance but in reality very minutely 

 hispid, harsh to the touch, fairly even. Dermal memhrane fairly distinct, but reduced 

 to a network by the very numerous pores. Oscula small, very abundant, irregularly 

 scattered, each on the summit of a small projection. Pores; the surface of the sponge, 

 as already stated, is minutely reticulate ; it is divided into a number of oval meshes by a 

 network of tissue; each mesh is about 0-2 mm. in diameter and is subdivided into smaller 

 meshes by the delicate, cribriform dermal membrane which stretches across it ; there are 

 thus larger and smaller meshes, the larger meshes containing some half dozen of the 



