DE. WYVILLE THOMSON ON HOLTENIA. 
713 
Genus 1. Euplectella, Owen. 
E. aspergillum, Owen. 
Genus 2. Habrodictyon, Wyville Thomson. 
1). azorica, Gray (sp.). 
D. (”?) torva, Duchassaing and 
Michelotti (sp.). 
H. speciosum, Quoy & Gaimard (sp.). Genus 5. Earrea, Bowerbank. 
H. corbicula, Valenciennes (sp.). 
Genus 3. Aphrocallistes, Gray. 
F. occa, Bowerbank. 
Genus 6. Holtenia, Wyville Thomson. 
H. Carpenteri, Wyv. Thomson. 
Genus 7. Hyalonema, Gray (in part). 
A. beatrix, Gray. 
A. bocagei, Wright, MSS. 
Genus 4. Dactylocalyx, Stutchbury. 
D. pumicea, Stutchbury. 
D. subglobosa, Gray. 
I). Prattii, Bowerbank. 
D. callocyathes, Gray (sp.). 
H. Sieboldi, Gray. 
[H. lusitanicum, Gray. 
H. Loveni (sp. nov.). 
Genus 8. Adrasta, (gen. nov.). 
A. infundibulum (sp. nov.)*. 
The characters which the vitreous sponges possess in common are sufficient to combine 
them into a very natural order. In all, the sarcode is in comparatively small quantity, 
and spreads in a thin translucent layer over the spicules or network of a highly deve- 
loped siliceous skeleton. In all the known genera all the spicules, whether of the 
skeleton or of the sarcode, are modifications of the hexradiate stellate type. In Fuplec - 
tella , Aphrocallistes, Dactylocalyx , and Farrea, large hexradiate spicules are more or 
less completely soldered together, and form a continuous anastomosing network. In 
Eabrodictyon, Holtenia, Hyalonema, and Adrasta, the skeleton is composed entirely of 
separate spicules, either distinctly hexradiate or quinqueradiate, or triradiate, or 
simple, by the suppression of one or more of their secondary branches. The sarcode of 
the inhalent and exhalent surfaces, and of the substance of the sponges, always contains 
scattered through it, numerous very minute spicules of very characteristic forms. In 
Aphrocallistes , one of the most abundant forms of these spicules of the sarcode is a 
regular six-rayed star with the principal axis longer than the transverse rays and one 
half of it feathered. In Holtenia, Adrasta, and Hyalonema , a spicule of the same type 
is common, but one half of the axis is undeveloped, so that the spicule has become 
quinqueradiate. In Euplectella, Habrodictyon, and Dactylocalyx, there are several modi- 
fications of a very complicated and beautiful spicule, the floricomo-hexradiate of Bower- 
bank. The most remarkable spicule, the double grapnel (Plate LXV1II. fig. 15), seems 
to be the most widely diffused of all in the order. It varies little in form in Hyalonema, 
Holtenia, and Adrasta, in all of which it is abundant ; and modifications differing only 
in the number, the curve, or the proportions of the flukes, or in the relative length of 
* Since this list was written a number of additional vitreous sponges have been described by Dr. Bowerbank 
and by Professor Barboza de Bocage ; and several new forms have been added from the rich collections made hy 
M. de Potjrtaees in the Strait of Florida in connexion with the American Coast Survey, and by the Naturalists 
in charge of the ‘ Porcupine ’ deep-sea dredging expedition. The sponges collected by M. de Pourtales are in 
the hands of Professor Oscar Schmidt for description; and a report on those procured by the English expe- 
dition is in course of preparation by the writer. 
