328 Contributions to our Knowledge of the Spongida. 
Observations on Classification. 
Now although the terms of my classification (‘ Annals,’ 
1875, vol. xvi. p. 126 et seg.) may be very plain to myself, who 
have carefully examined each of the specimens in the British 
Museum, including those lately purchased from Dr. Bower- 
bank’s executors, in all amounting in cubic measurement to 
three or four yards, or sufficient to fill a small room of this 
size—consisting of thousands of specimens from various parts 
of the world, most of which are still undescribed,—yet these 
terms may not be so plain to those whose observation in this 
respect has been confined to their own cabinets, which can 
hardly be expected to afford so much general knowledge; 
therefore, before any determined opposition is made to my 
classification I trust it may be based on a similar amount of 
practical experience, when such criticism ought to be very 
valuable ; for I do not wish to insist on my views any further 
than as the best wnder the circumstances that I could offer, 
therefore still open to great improvement. When the Spon- 
gida shall have been worked upon as much as the Plants, then 
their classification may be expected to be as satisfactory. 
EXPLANATION OF THE PLATES. 
N.B.—The spiculation of the Ectyones, together with that of Eetyo- 
nopsis, is all on the same scale, viz. 1-12th to 1-6000th inch, chiefly to 
show their sizes relatively. That in Pl. XIV. is all on one scale also, 
viz. 1-12th to 1-1800th inch, for the same purpose ; with the exception, 
however, of the flesh-spicules ¢ and d, fig. 10, which are on the scale of 
1-12th to 1-6000th, and the spicules &c. of the Diluvium from the 
valley of the Altmihl river, in Bavaria, whose scales respectively are 
stated in loco. 
Puate XI. 
Fig.1. Ectyon flabelliformis, n. sp. One sixth of the natural size. 
From a photograph. Specimen in the Liverpool Free Public 
Museum. a, spicule. West Indies. 
IPTADE XG: 
Fig. 2. Ectyon sparsus, var. claveformis, n. var. Less than one third of 
the natural size. From a photograph. Specimen in the Liver- 
pool Free Public Museum. a, spicule; 6, vents; c, small 
congregated foramina; d, clathrous openings. West Indies. 
Fig. 3. Ectyon mauritianus, n. sp. a, spicule, lateral view ; 6, transverse 
section. Mauritius. 
PuaTeE XIII. 
Fig. 4. Ectyon cylindricus, n. sp. (fragment), nat. size. a, lateral view ; 
6, transverse section; c, spicule; d, vents; e, parasitic polyp. 
West Indies. 
