REPORT ON THE TETRACTINELLIDA. 
XCVll 
Suborder II. Tetractina (identical with our Choristida). 
Suborder III. Oligosilicina (including as families the Chondrosidse and 
Halisarcidse). 
Suborder IV. Pseudotetraxonia (a single family, the Tethyidse). 
Suborder V. Clavulina (including as families the Polymastidm, 
Suberitidse, and Clionidm ; the last provisional). 
Order III. Cornucospongise. Skeleton consisting either of monaxon spicules 
cemented together by spongin, or only of spongin, which may or may not 
incorporate foreign bodies. 
Suborder I. Halichondridse (including the families Halichondridse, 
Spongillidse, Desmacidonidse, and Ectyonidse). 
Suborder II. Ceratina (including the families Spongelidse, Spongidae, 
Aplysillidse, and Darwinellidse). 
The line of separation between the Spiculispongiae and the Cornucospongiae would 
appear from this classification to be as marked or nearly so as that between them and 
the HexactineUida. 
Lendenfeld’s classification is as follows : — 
Subclass Silicea (equivalent to our Micromastictora). 
Order I. HexactineUida, 0. Schmidt. 
Order II. Chondrospongiae, Lendenfeld. Mesogloea hard. Spicules tetraxon, 
monaxon, anaxon, or absent ; generally corticate. 
Order III. Cornucospongiae, Yosmaer. Mesogloea soft. (The rest of the definition 
is similar to Vosmaer’s.) 
It will be seen that the character on which Vosmaer chiefly relies in distinguishing 
the two orders Spiculispongiae and Cornucospongiae is the presence of spongin in the 
latter and its absence in the former. This character is, however, by no means absolute, 
for spongin occurs in several Sponges of the order Spiculispongiae ; setting aside 
Monaxonid species of the order, in which it is nevertheless present, I need now only 
indicate the Lithistida, e.g., Theonella swinhoei, and the Choristida, e.g., Pcecillastra 
[Normania) schulzii, as possessing spongin which unites some of the spicules together. 
But even were this not the case the two groups so evidently pass into each other that 
it is difficult to understand how two investigators, so intimately acquainted with the 
species of both orders, should expect to be able to separate them thus sharply ; any 
line drawn between them must be one of mere convenience, and consequently not of 
the same value as that between them and the HexactineUida, nor indeed in any way 
comparable. 
But, it may be enquired, what of the additional character alleged by Lendenfeld to be 
(ZOOL. CHALL. EXP. — PART LXIII. — 1888.) Rrr n 
