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



biliamate or C-sliaped flesh-spicule, sometimes without any flesh-spicule at all. Forms 

 massive, lobo-branched ; branches compressed, dichotomous, separate or anastomotic, 

 flabellate proliferous." On page 195 of the same volume the author gives " Halichondria 

 plumosa, Johnst. { = Hymeniacidon 2^lui^'>-0sa, Bowerbank) " as an example of this 

 group. 



In voL xviii of the same periodical (1876, p. 236) we first meet with the generic name 

 " Plumohalichondria " in the description of the species named by Mr. Carter " Plumo- 

 halichondria microcionides" ; but we find no generic diagnosis. Under these circum- 

 stances it has appeared to us advisable to retain the genus, which suppUes a great want 

 in the classification of the Mouaxonida, and to give a generic diagnosis as above. Thus 

 constituted, the genus appears to be fairly compact and well characterised; it includes a 

 portion of Bowerbank's \&xj heterogeneous genus " Microciona " ^ and certain other 

 forms. 



As examples of sponges which belong to the genus " Plumohalichondria," we 

 may give Plumohalichondria microcionides, Carter, and Plumohalichondria mam- 

 millata. Carter." 



Plumohalichondria mammillata, Carter (PI. XXX. figs. 4, 4a; PI. XLVII. figs. 4, 4«). 

 1885. Plumohalichondria mammillata, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. xvi. p. 355. 



Sponge (PI. XXX. fig. 4) massive, with erect, compressed and rounded lobes. Height 

 94 mm., breadth 137 mm. Colour in spirit pale, yellowish-grey. Texture compact 

 but soft and spongy. Surface glabrous but rather uneven and lumpy. Dermal 

 membrane distinct, much strengthened by the presence of a very well-developed 

 dermal reticulation of spicules. Oscula scattered ; round openings, about 2 mm. in 

 diameter, with their margins sometimes surrounded by a slight, projecting, membranous 

 collar ; sometimes flush with the general surface of the sponge, but usually sunk a little 

 below the surface. Pores very numerous, thickly scattered, rounded openings ; about 

 0"07 mm. in diameter. 



Skeleton. — (a) Dermal; a very regular and definite reticulation (PI. XLVII. fig. 4) 

 of small, spined, stylote spicules ; the meshes of the network are roundedly polygonal 

 and only about O'l mm. in diameter, and each side is of about one spicule's length ; the 

 " fibre " (if we may be allowed to use a term which does not seem very applicable to the 

 case in point) is composed of several spicules lying parallel side by side. (&) Main; 

 composed of plumose columns of spiculo-fibre (PI. XLVII. fig. 4a, p.c.) running towards 



1 Mon. Brit. Spong., vol. ii. p. 124. 



- The genus Plumohalichondria, Carter, must not be coufoundeJ with the genus " Aulospongus," Norman, which was 

 founded (Ann. and Mag. Nat. Hist., ser. 5, vol. i. p. 267, footnote) for tlie reception of Bowerbank's " Ealiphipema 

 tubulatum," a remarkable sponge from Ceylon, which has some resemblance to Plumohalichondria but has no chelate 

 nor oxeote spicules and is probably a very different thing. 



