REPORT ON THE MONAXONIDA. 199 



below, possibly indicate a real alliance between the species. The single specimen is 

 remarkable for the presence of a great number of large, nucleated sperm-cells (?), which 

 are closely packed together, so as almost entirely to fill the soft parts of the sponge. 

 Locality. — Off Marion Island ; depth, 50 to 75 fathoms. One specimen. 



We have from Station 320 an interesting series of specimens which should perhaps be 

 considered as belonging to a slight variety of the above species ; they do not, however, 

 appear to be distinct enough from the tyjje to justify us in giving a varietal name. 

 They occur, for the most part, encrusting dead branches of a Sporadopora, on which 

 they form colonies (PI. XLI. fig. 2), the different cushion-like individuals being united 

 together by their bases ; there is usually more than one osculum to each individual, 

 situated at or near the summit of the sponge. The growth appears to be altogether 

 rather more robust and the spicules of a rather larger average size than in the type. We 

 noticed in this variety a feature which we had not observed in the type, namely, that 

 towards the base of the sponge the cortical layer of projecting brushes of tylostylote 

 spicules gives place to a confused layer of short, stout, fusiform tylostyli, calling to mind 

 the similar layer in Tentorium semisiiherites. The sponge is further remarkable as forming 

 colonies by continuous gemmation, in a manner very rare in siliceous sponges. 



Locality.— ^tsLtion 320, February 14, 1876 ; lat. 37° 17' S., long. 53° 52' W.; ofi'the 

 mouth of the Eio de la Plata ; depth, 600 fathoms ; bottom, green sand ; bottom 

 temperature, 37°"2. Several specimens. 



Suherites microstomus, n. sp.^ (PI. XLI. fig. 3). 



Sponge (PI. XLI. fig. 3) sessile, hemispherical. The single specimen in the collection 

 is about 25 mm. in diameter and is attached to a piece of black, volcanic rock. Colour 

 in spirit pale yellow. Texture very firm and dense, with a very strongly developed, 

 fibrous cortex (ectosome) about 0'9 mm. thick. Surface fairly even, minutely granulated. 

 Oscula very minute, but distinct, very slightly raised above the general surface of the 

 sponge and with no thin- walled tubular projections as in Suherites caminatus, nobis {cf. 

 woodcut. Fig. 7 and PI. XLI. figs. 2, 3). Pores, small openings between the cortical 

 brushes of spicules, leading into large, elongated, rather lacunar subdermal cavities in the 

 cortex. 



Skeleton. — The main skeleton is very well developed and composed of very stout 

 bands of spiculo-fibre, which radiate to the surface, expanding at their ends in a brush- 

 like manner and merging in a distinct cortical layer composed of dense brushes of much 

 smaller, radiately disposed spicules, whose apices project for some distance l^eyond the 

 surface of the sponge. It is important to notice that the special cortical layer of spicules 



This is the sponge referred to in our Preliminary Report (Ann. and Mag. Nat. Hist, ser. 5, vol. xviii. p. 485) as 

 a slight variety of Suherites caminatus, nobis, with very small, non-tubular oscula. 



