THE VOYAGE OF H.M.S. CHALLENGER. 
cii 
Order I. CHORISTIDA, Sollas. 
History. — The first tendency towards a segregation of the Choristida from chaos 
appears in Oscar Schmidt’s work on the Sponges of the Adriatic.^ Here we find, together 
with one Monaxonid genus [Tethya), four genera of Choristida {Stelletta, Caminus, 
Geodia, and Ancorinob), gathered together into a single family, the Corticatse, and one 
more {Corticium) in another family — the Gumminese. 
In the third ^ supplement to this work Schmidt instituted another Choristid genus, 
Pacliastrella, which, though placed in a third family, the Compaginase, is shown to be 
related to the Corticatse and Gumminese. 
In his next work^ Schmidt recognised that the cortex has not that value which he at 
first assigned to it, so that the family Corticatse is there definitely abandoned, and all the 
Choristid Sponges there described appear in two families, the Ancorinidse, which includes 
the following genera : — Pachastrella, SpJiinctrella, Tetilla, Craniella, Ancorina, and 
Stelletta; and the Geodinidse, which includes the following : — Geodia, Pyxitis, Caminus, 
and Placospongia. Further the genus Corticium is removed from the Gumminese and 
placed with the Sponges characterised by anchor-like spicules, a roundabout expression, 
as here used, for our Choristida. 
In the system of the Sponges proposed by Carter* the Choristid Sponges are collected 
into two closely related families, in one of which, however, the Lithistida are also 
included ; these are the Pachytragidse, which contains our families Geodiidse, Stellettidse, 
and Tetillidse ; and the Pachastrellidse, which contains our Lithistida and Pachastrellidse. 
But for the association of the Lithistids too closely with the Pachastrellids this classifica- 
tion exhibits an advance upon Schmidt’s, since the difference between the Geodiidse and 
the Stellettidse is not so wide as Schmidt’s system implies, and these two families may 
well be grouped together ; the recognition of the Tetillidse as forming a group apart from 
the other members of Schmidt’s Ancorinidse is also justified by later observations ; the 
inclusion of the Lithistids with the Pachastrellidse, though going too far, errs in the right 
direction, for it correctly indicates that the Lithistids are more closely allied to the 
Pachastrellids than to any other Sponges. 
Marshall having included the Sponges of Carter’s two families into the single large 
group, Tetractinellida, the separation of the Choristids from this was made as already 
indicated by Sollas. 
In his latest work'^ Schmidt definitely abandoned the Ancorinidse and Geodiidse as 
distinct families, and adopted the group Choristida, but under the name Tetractinellida. 
The Choristida, by whatever name we know them, having thus become definitely 
^ 0. Schmidt, Spong. Adriat. Meeres, pp. 37, 42, 43, 81, 87, 1862. 
2 0. Schmidt, Spong. d. Kuste v. Algier, p. 40, 1868. ^ 0. Schmidt, Spong. Atlant. Gehiet., p. 64, 1870. 
^ Carter, Ann. and Mag. Nat. Hist, ser. 4, vol. xvi., 1875. 
® 0. Schmidt, Spong. Meerb. Mexico, pt. ii. p. 68, 1880. 
