REPORT ON THE TETRACTINELLIDA. 
cxv 
Order II. LITHISTIDA, 0. Schmidt. 
Historical. — The earliest description of a recent Lithistid sponge, Macandrewia 
azorica, we owe to Gray, who was not unnaturally greatly puzzled as to its nature ; 
struck by the resemblance of its oscules to the calyces of an Alcyonarian, he was much 
inclined to place it with the Alcyonaria, but cautiously refrained from actually doing so, 
since he was unable to find any traces of the polypes.^ Bowerbank would seem to have 
been the first to definitely include the Lithistida with the Sponges,^ but he did not 
distinguish them from the Hexactinellida, and this, and his failure to understand the 
true nature of the skeleton either in the Hexactinellida or the Lithistida, led him into 
numerous errors ; not only did he class together these two widely different groups in the 
same suborder, the fibro-siliceous Sponges, but he placed species belonging to both 
in the same genus; thus the genus Dactylocalyx, instituted by Stutchbury to contain 
the HexactineUid species Dactylocalyx 'pumiccus, must be carefully distinguished 
from the genus Dactylocalyx of Bowerbank, which in addition to this species contained 
several others which are genuine Lithistids. This fact was not recognised by succeeding 
writers for some years, and thus we find Gray in his' classification of the Sponges^ 
including both HexactineUid and Lithistid Sponges in his order Coralliospongia, and 
adopting the Bowerbankian genus Dactylocalyx, with its heterogeneous mixture of 
species belonging to two groups of difierent subclasses. Similarly Wyville Thomson, in 
an account of the Vitrea, an order proposed by him, falls into the same error. ^ 
Duchassaing and Michelotti in 1864 instituted a family Lithospongise, but from its 
definition it might include HexactineUid as well as Lithistid Sponges, and from the 
illustration given of the only species of the group known to them, I am inclined to think 
that it was actually based on a HexactineUid Sponge.^ 
In 1869 Bowerbank® largely added to our knowledge of the species of the order, but 
included them all but one in the genus Dactylocalyx; in the same year^ Bocage rescued 
one species from this omnivorous genus, to which he tells us Bowerbank had intended to 
devote it (as indeed he did in the Memoir just referred to, which was published slightly 
later than Bocage’s description). This species was made the type of a new genus, 
Discodermia, under the name of Discodermia polydiscus. 
The next great step in advance was made by 0. Schmidt,® who brought the Lithistid 
1 Gray, Froc. Zool. Soc. Land., p. 437, pi. xv., 1859. 
^ Bowerbank, Phil. Trans., p. 279, 1858. 
3 Gray, Proc. Zool. Soc. Lond., p. 472, 1867. 
Wyville Thomson, Ann. and Mag. Nat. Hist, ser. 4, vol. i. p. 119, 1868. 
® Duchassaing and Michelotti, Spongiares d. 1. Mer Caraibe, p. 64, pi. xii. figs. 3, 4, 1864. 
8 Bowerbank, Proc. Zool. Soc. Lond., p. 66, 1869. 
^ Bocage, Jorn. Sci. math. phys. e nat. Lisboa, vol. ii. p. 160, pi. xi. fig. 1, 1869. 
8 0. Schmidt, Spong. Atlant. Gebiet., p. 21, pi. iii., 1870. 
