EEPORT ON THE MONAXONIDA. 113 



ments ; without knowledge of this important character identifications are usually a very 

 difficult matter ; the figures and description of the external form and spiculation of 

 this sponge are, however, sufficient to convince us that we have really got hold of the 

 same thing, and this conviction is strengthened by the fact that both specimens come 

 from high northern latitudes. 



The spiculation (taken from the Challenger specimen, for we have had no 

 opportunity of examining the original type) is as follows : — (a) Megasclera ; of one 

 kind only, viz., smooth, slender, straight subtylostyli, with slightly developed oval 

 heads, and tapering gradually to a fine point at the apex ; size about 0*6 by 0"0075 mm. 

 (6) Microsclera ; of two kinds ; (l) minute isochelse, very abundant, about 0'0r26 mm. 

 long ; (2) slender toxa, with spined ends, size very variable, apparently reaching as 

 much as about 0'4 mm. in length (as shown by a single broken spicule, of which one 

 limb was measured and doubled to give the total length), commonly much smaller, 

 about 0"15 mm. long. 



Locality. — Station 49, May 20, 1873 ; lat. 43° 3' N., long. 63° 39' W.; south of 

 Halifax, Nova Scotia ; depth, 85 fathoms ; bottom, gravel, stones ; bottom temperature, 

 35°"0. One specimen, attached to a stone. 



Habitat. — Arctic Seas (Vosmaer) ; south of Nova Scotia (Challenger). 



Genus Phelloderma,^ Eidley and Dendy (PI. XXIII.). 

 1886. Phelloderma, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 347. 



Corticate, with a cork-like ectosome. Megasclera aU monactinal, styli or tylostyli, 

 radiating towards the surface, with the points directed outwards ; microsclera 

 isochelse. 



In the presence of a distinct cortex, and in the radiate arrangement of its skeleton, 

 this genus approaches the Suberitidae, but its stylote megasclera and isochelate 

 microsclera leave no doubt that its real place is amongst the Desmacidonidse. Although 

 there is only a single specimen, yet its characters are so well marked that they appear 

 to us to justify the erection of a new genus for its reception. 



Phelloderma radiatum, Eidley and Dendy (PI. XXIII. figs. 8, 8«, 86, 8e, 8c7). 



1886. Phelloderma radiatum, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. 



p. 347. 



Sponge subglobular, with a concave base of attachment (originally based upon a 

 Sporadopora, from which it has been removed), about 13 mm. in diameter, with a 



1 From Greek (ps^Xof, cork ; and oi^/ia, .skin. 

 (ZOOL. CHALL. EXP. — PAET Lix. — 1887.) Nnn 15 



