REPORT ON THE TETRACTINELLIDA. 
XCIX 
The subdivision of the Demospongise may be made primarily into two tribes, the 
Tetractinellida and the Monaxonida, the latter including as orders the Monaxona, ^.e., 
Monaxonida in which a spicular skeleton is present, with or without spongin in addition ; 
and the Ceratosa, which do not possess spicules, but only a spongin skeleton ; since, 
however, the Ceratosa are evidently and admittedly directly descended^ from the 
Monaxona, they are naturally included in the same tribe ; though objections may be 
readily found to giving to this the name Monaxonida, its justification lies in the fact that 
it indicates the descent of the tribe, and further, that it stands in convenient opposition 
to the term Tetractinellida, by which the second tribe is designated. 
The classification of the Tetractinellida will form the subject of a separate heading. 
Classification of the Teteactinellida. 
The Tetractinellida are Demospongise in which some or all of the scleres are tetraxons 
triaenes, or desmas. 
The name was first proposed in substantially the same sense as it is employed here by 
Marshall,^ who expressly stated that he intended by it to include both Choristid and 
Lithistid Sponges, though he does not use these names. 
It was subsequently adopted by Zittel,® but with an altered and restricted meaning, 
since it was made to apply to the Choristid Sponges only, the Lithistids being excluded, 
on the erroneous supposition that no very close connection could be shown to exist between 
the two groups. 
The term was next accepted by myself,^ its original sense being retained ; this 
rendered necessary the subdivision of the group it denotes into two, which were named 
Choristida and Lithistida. Later® a more elaborate classification was proposed, which, 
though supported in its main outlines by the results of subsequent investigations, is here 
abandoned in favour of another. 
Schmidt ® also adopted the term, but in the restricted sense proposed by Zittel. 
Vosmaer^ also, but with a change of form to Tetractina ; since the Tetractinellida of 
^ SoUas, Cassell’s Natural History, Spongiae, p. 328, 1881. I here give the exact words in. which this view was 
first expressed ; — “ This family {Chalinidx) indeed links together the Silicispongise and the Cerospongiae, and since its 
spicules must apparently be formed before the spongin which envelopes them, it would appear rather that the 
Cerospongiae were derived from the Silicispongiae by loss of spicules, than the latter from the former by their 
acquisition.” See also Vosmaer, Mitth. a. d. Zool. Stat. Neapel, p. 490, 1884 ; Schulze, Ahhandl. d. k. preuss. Akad. d. 
Wiss. Berlin, p. 33, 1886 ; Lendenfeld, Proc. Zool. Soc. Bond., p. 571, 1886 [1887]. 
“ “ der vereinten Lithistiden-Corticaten-gruppe, die den Namen der Tetractinelliden ftihren mag, . . . . ” 
Marshall, Zeitschr. f. wiss. Zool, Ed. xxvii. p. 134, 1876. 
® Zittel, Zur Stammegeschichte der Spongien, Munich, 1879. 
^ Sollas, Ann. and Mag. Nat. Hist., ser. 5, vol. vi. p. 386, 1880. ® Sollas, op. cit, vol. ix. p. 164, 1882. 
® 0. Schmidt, Spong. Meerh. Mexico, p. 68, 1880. 
’’ Bronn’s Klass. u. Ord. d. Thierreichs, Porifera, p. 315, 1885. 
