SPONGES.-HALLMANN. 21^ 



in short strands. In other respects the main skeleton agrees, 

 with that of the preceding species, C. ccelata; that is to say, 

 the pnncipal styh of the fibres are arranged more or less semi- 

 plumosely and frequently assume the attitude of echinating 

 spicules ; the superficial transverse fibres are closely echinated' 

 on their outer aspect by both accessory and principal styli ; 

 and, finally, the pnncipal and accessory megascleres are con- 

 nected by a series of spicules of intermediate form. The 

 passage between the two kinds of megascleres is, however, 

 more abrupt than in C. ccelata, and transitional forms are 

 rarely met with except amongst the spicules which echinate 

 the superficial fibres. In two respects the species differs 

 markedly from C. ccelata ; firstly, in the absence of tricurvate 

 toxa ; and, secondly, in the presence of a well-developed dermal 

 skeleton in the form of a thin layer of closely packed hori- 

 zontally-disposed auxiliary subtylostyli, which in the dry state 

 forms a whitish incrustation similar in appearance to that 

 shown by species of Rhaphidophlus. 



Megascleres. — 



(i.) The principal styli are curved or (less frequently)" 

 straight subconical smooth spicules, varying in length 

 from about 120 to 300^1 and in diameter up to loji ; 

 the stoutest are usually those of intermediate length, 

 say from 220 to 250 ft. The shortest often exhibit a 

 slight degree of ruggedness or other surface in- 

 equality, which rareh' extends for more than a short 

 distance from the basal extremity and is seldom met 

 with in individuals of greater length than 160 ft. A 

 certain proportion show a slight basal knob marked 

 off by a faint constriction ; this is of relatively larger 

 size in smaller and slenderer individuals, which are 

 then subtylostyli sometimes scarcely distinguishable 

 from the shorter auxiliary spicules. 



(ii.) The accessory acanthostyles are straight or slightly 

 curved subconical spicules occasionally with a slight 

 basal knob. In length, they range from 40 p to 120 ji 

 though usually less than 90 ^. Individuals above 

 100 ji long are comparatively rare, and are inter- 

 mediate in form between the accessory spicules proper 

 and the principal spicules. The accessory spicules 

 proper are minutely spined over their whole length or, 

 like those of intermediate form, are merely rugged. 



(iii.) The auxiliary subtylostyli (or, less frequently, simple 

 styli) are straight or curved spicules, varying in length 

 from less than 160 >i to 380 ji and in diameter up 

 to 6 }i. 



