1869.] DR. J. S, BOWERBANK ON SILICEO-FIBROUS SPONGES. 333 
attenuated to a sharp point. In size, compared with those I have 
previously described in a fragment of the membranous tissue, they 
are small and slender. 
The genera of the two sponges I. Ingalli and Daetylocalyx pumi- 
ceus being distinctly different, it is unnecessary to enter into a long 
description of their differential characters to prove that Dr. Gray is 
in error in assigning the type specimen of the former to the latter 
genus; but it may be as well to state that none of the singular and 
beautiful forms of spicula which I have obtained from the type speci- 
men of D. pumiceus, and have figured in Plate III., part 1, are to be 
found in the tissues of the type specimen of I. Ingalli. 
IpHITEON CALLOCYATHES, Bowerbank. 
Myliusia callocyathes, Gray, P. Z. 8. 1859, p. 439, Radiata, 
pl. xvi. 
Sponge sessile or slightly pedicelled, cyathiform. Upper surface of 
rigid skeleton even ; under surface sinuously plicated and tubulated. 
Oscula and pores unknown. Expansile dermal system—dermal mem- 
brane pellucid, furnished abundantly with minute short, stout, acerate 
tension-spicula ; connecting spicula furcated foliato-expando-ternate. 
Skeleton—fibre variable in diameter, verticillately spinous, spines 
small, acutely conical ; interstitial spicula rectangulated hexradiate, 
axial and_rectangulating radii nearly equal in length, slender, termi- 
nations subclavate; retentive spicula spinulo-multifurcate hexra- 
diate stellate, terminations of each heptaradiate or octoradiate; of two 
sorts, one with terminal radii expanded, the other with terminal 
radii contracted into separate groups. 
Colour in the natural state unknown. 
Hab. West Indies (Dr. M‘Gee). 
Examined in the skeleton-state. 
In the description of the external characters of this sponge it must 
be remembered that it is that of the rigid skeleton only, and that it 
is probable that both surfaces would be more or less smooth and even 
when covered by the expansile dermal system. 
The arrangement of the skeleton is decidedly that of an Ipiiteon ; 
but the structural character of the fibres of which it is composed 
is strikingly distinct from any other species of the genus. ‘They are 
variable in size to a considerable extent ; but whatever may be their 
diameters, they are always furnished with numerous small sharply 
conical spines, which exhibit a strong tendency to a verticillate ar- 
rangement ; and around the central umbones of the confluent areas 
of the skeleton they are frequently congregated on slightly elevated 
detached patches, each containing from seven to ten minute spinules. 
These structural characters would have sufficed, in the present 
state of our knowledge of the species of this genus, to distinguish 
it from any other member of the group; but, by a careful exami- 
nation of the type specimen, I fortunately obtained from near the 
base of the sponge on the inner surface a small piece of the ex- 
pansile dermal system in connexion with a portion of the surface of 
