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



in other EuspongicB the i^rimary fibres run usually more or less parallel to one another, 

 here they show a very pronounced tendency to ramify ; the spaces between them and 

 their secondary, but still vertically directed, branches lieiug filled with an irregular 

 network of fibres originating also from the primary ones, but in a more or less horizontal 

 direction. The average basal diameter of the primary filires is O'l mm., that of the 

 tertiary only 0"03 mm. The latter, in contrast to the primary fibres, are in most cases 

 quite free from foreign enclosures. This variety is a connecting link between Euspongia 

 officinalis and Cacospongia moUior , and maybe classed in the species last mentioned with 

 the same right as in Euspongia officinalis. 



Colour. — Outer surface pale greyish, parenchyma colourless, fibres' straw-yellowish. 



Habitat. — Bahia, shallow water. 



Hippospyongia, F. E. Schulze. 



Spongidse with fine skeletal fibres and small meshes, the fibres admitting of no 

 distinction into primary and secondary ones ; distinguished by a system of canals 

 permeating the body in all possible directions. 



Hipposp)ongia anomala, n. sp. (PI. YII. ; PI. VI. fig. 2). 



This species is represented in the Challenger Collection by a single but very large 

 specimen 350 mm. broad, 200 mm. high, and 40 mm. thick, drawn of the natural size, but 

 in a bent position on PL VII. For its characters, common to the whole genus, I refer 

 to the diagnosis in the foregoing paragraph. The character distinguishing it from other 

 species of the genus is a property which renders its grouping in the genus Hip)pospongia 

 rather disputable. I mean the presence of quite distinct primary fibres directed obviously 

 towards the outer surface, on an average four times as thick as the others, and absent 

 only in the skeleton supporting the thin membranes covering the lacuna immediately 

 under the outer surface. It must be said that the terminal skeletal processes of a 

 Hippospongia equina, when seen with the naked eye, show within them certain 

 streaks perpendicular to the outer surface ; but these streaks and the fibres in question of 

 my Hippospongia anomala are quite difi"erent things, the last-mentioned being really 

 nothing but single fibres thicker than the others, the first-mentioned being composed of 

 many fibres and difierentiated from the surrounding parts of the skeleton by the fact that 

 the network formed by the fibres is here more compact than elsewliere. The aj)2iearauce 

 is therefore only an optical illusion ; at any rate the property in question distinguishes 

 my species readily from all others of the genus, but does not, however, decide the 

 question whether it really belongs to the genus Hijjpiospongia. Still I am of this opinion. 

 As regards the rigidity of the skeleton this specimen is, indeed, allied to Cacospongia 

 mollior ; but apart from distinctions concerning the presence of the system of canals 



