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



Finally Bowerbank again gave, in 1869/ a more minute description of his 

 Farrea occa, and supplied three new figures on pi. xxiv. figs. 1, 7. In this latter 

 very detailed communication the siliceous network with its Cjuadrate meshes, regarded as 

 dermal skeleton and compared in form to "a harrow, is represented by Bowerbank just as 

 formerly ; on the other hand, in addition to the more irregular and rough network of 

 beams regarded as belonging to the inner framework, a number of variously formed isolated 

 siliceous spicules are figured and described as accessory parts of the skeleton. These 

 have four, five, or more rays, and do not present the right angles of the Hexactinellidan 

 spicules. The generic characters of Farrea were summarised by Bowerbank in 

 the same paper (p. 76) in the following manner: — "Skeleton siliceo-fibrous. Fibres 

 canaliculated, canals continuous. Eete symmetrical ; interstices rectangulated." The 

 view first announced in the well-known paper by Wyville Thomson On the Vitreous 

 Sponges,^ is noteworthy ; it is to the effect that the framework of beams which in 

 the skeleton of Farrea forms a system with exactly square meshes has arisen by an 

 amalgamation of regular hexradiate spicules. 



Among the deep-sea sponges collected by Count Pourtales in the Caribbean Sea 

 Oscar Schmidt found in 1870^ several irregular dichotomously branched tubes from 

 2 to 6 mm. in diameter. These were attached by a plate-like expansion, were thick- 

 walled at the base, and became towards the wide open upper extremity gradually 

 thin-walled and fragile, till finally on the outermost and doubtless youngest parts of the 

 little tubular tree only a single layered network of siliceous beams and square meshes was 

 found. From the intersections of the latter rough slender conical teeth projected on 

 both sides. In addition to this siliceous network, which, in its youngest parts at least, 

 presents a certain resemblance to the harrow-Hke siliceous network of beams of Farrea 

 occa which Bowerbank regarded as a dermal skeleton, Oscar Schmidt also found and 

 described the following free siliceous spicules : — (1) long spindle-spicules beset with barbs ; 

 (2) long spicules which run out at one extremity to a point, and are provided on the 

 other with a hemispherical or slightly convex and marginally toothed umbel-like roof or 

 cap; (3) hexradiate spicules, in which each of the rays is beset on its extremity with three 

 pronged, thin teeth, with minute convex terminal umbels ; (4) thin spicules which run 

 out to a point at one extremity, and are provided on the other somewhat expanded 

 end with five to eight bristle-like narrow prickles which project in a brush-like manner. 

 These various spicules, which occurred in special abundance in the neigbourhood of 

 the surface, were regarded by Oscar Schmidt as sufiiciently characteristic of a new 

 species distinct from the Farrea occa of Bowerbank, and this he designated Farrea 

 facunda. 



In the same year (1870) Saville Kent described,* along with several other Hexac- 



1 Proc. Zool. Soc. Loud., p. 339. 2 ^,„[_ and Mag. Nat. Hist., 1868. 



* Spongien des Atlaatisohen Gebietes, p. 16. * Monthly Micr. Journ., November 1870. 



