1102 
DE. J. S. BOWEEBANK ON THE ANATOI^fY 
The structure of the peripheral system exhibits a close alliance with the genera Pachy- 
mafisma and Tethea. Ecionemia ditfers from Geodia and Pachymatisma in the total 
absence of the siliceous ovaries, and of the crustular dermal coat formed principally of 
those bodies in the last-named genera. There are also no cylindrical valvular inter- 
marginal caAuties, and the ternate apices of the connecting spicula appear always to be 
applied to the inner surface of the dermal membrane. This arrangement of the tissues 
therefore forms a natural transition from Pachymatisma to Tethea, in some species of 
which genus the ternate spicula are found without the dermal membrane in the porrecto- 
ternate form, and are adapted to defensive purposes, while in others they occur imme- 
diately beneath it as patento-ternate connecting spicula. I have therefore assigned this 
genus a position between Pachymatisma and JDictyocylindrus. Plate LXXIII. fig. 1. 
We have no British species of this genus ; the type species, Ecionemia acerms, Bower- 
bank, MS., is in the Museum of the Royal College of Surgeons of London. 
On the Genus Alcyoncellum, Quoy et Gaimard [Euplectella, Owen). 
Professor Owen, in his paper on Eujylectella aspergillum, Owen, communicated to the 
Zoological Society January 26, 1841, and published in the Transactions of the Zoolo- 
gical Society of London, vol. hi. part 2. p. 203, pi. 13, appears to have fallen into a 
singular number of errors in the course of his description of this beautiful sponge. He 
has, in the first place, designated it as belonging to the Alcyonoid family, apparently 
only because it is cylindrical in form and reticulate in structure, but -without the 
slightest reference to the polyps that must necessarily characterize an Alcyonium ; and 
he proceeds in his description to describe the base of the sponge as its apex and the 
apex as its base. The author then notices the first specimen of this genus that was 
made known to us by MM. Quoy and Gaimard, in the ‘ Zoologie de I’Astrolabe,’ 8vo, 
1833, p. 302, planches fol. Zoophytes, pi. 26. fig. 3, but unfortunately mistakes the 
generic name Alcyoncellum, applied to the sponge by the French authors, for Alcyonel- 
lum ; and ha-vdng mistaken its name, its base, and its apex, he proceeds to reason on its 
generic characters thus : — “ If the basal aperture of the cone were open, the resem- 
blance to some of the known reticulate Alcyonoid sponges would be very close, espe- 
cially to that called Alcyonellum gelatinosum by M. de Blainville, ‘ Manuel d’Actino- 
logie,’ 8vo, 1834, p. 529 [Alcyonellum speciosum, Quoy et Gaimard): its closure by the 
reticulate convex frilled cap, in the present instance, establishes the generic distinction ; 
and in the exquisite beauty and regularity of the texture of the walls of the cone, the 
species surpasses any of the allied productions that I have yet seen or found described. 
I propose, therefore, to name it Euplectella aspergillum'' In note 5 appended to this 
paper, Professor Owen also says, “ If the recognition of the generic or specific identity 
of the specimen here figured be impracticable by reason of its mutilated condition, the 
generic name applied to it cannot be adopted while the Lamarckian genus of freshwater 
polyps, Alcyonella, is retained in Zoology.” Now as it is manifest that the reasoning of 
