356 Mr. H. J. Carter’s Contributions 
optical delusion will be discovered and the spiral arrangement 
in most instances satisfactorily recognized. 
I have already noticed the smooth form of this spirula under 
the name of “ sinuous subspiral ” ( a Notes,” &c. p. 32), which 
is well seen in Cliona abyssorum (Ann. 1874, vol. xiv. p. 249, 
pi. xiv. fig. 33). 
As regards the extent to which the Spinispirula under 
various forms occurs among the Spongida, I have as yet not 
seen it in any of the orders but that of Holorhaphidota—and 
here confined to the families Suberitida, Pachytragida, and 
Pachastrellida, where it is very common among the groups 
Cavernosa, Compacta, and Laxa,and also in Placospongia melo- 
besioides , which may have to come into the same family ; rarer 
in the Pachytragida, where its great abundance, though, and 
almost peculiar form, in Tethea muricata , Bk. ( = Wyvillethom- 
sonia Wallichii , Wright), becomes a character, as first shown 
by the late Dr. Bowerbank (Phil. Trans. 1862, pi. xxxi. 
figs. 14,15)—used again by him as an illustration of this kind 
of spicule, described and represented under the designation 
of “ elongo-attenuato-stellate” (Mon. Brit. Sp. vol. i. p. 233, 
pi. i. fig. 35); also abundant, but in a minuter form, in 
Stelletta aspera (Ann. 1871, vol. vii. p. 7, badly illustrated). 
Minute, although constant and varied in form, in the Pachas- 
trellina, and present also in some of the Corallistes, ex gr. 
Dactylocalyx Masoni , Bk. ( l. c.). 
As the C-shaped bihamate flesh-spicule or fibula is con- 
tortly subspiral, and not simply bent upon itself, which may 
be seen by viewing it on a flat surface, while the S-shaped 
form is still more spiral, the latter when spined throughout, 
as in some species of Tethyina (Ann. 1876, vol. xviii.pl. xvi. 
fig. 49), literally becomes a spined spire ‘ but for memory’s 
sake the line of distinction must be drawn somewhere, and 
therefore this had better be still considered as a variety of the 
bihamate rather than one of Spinispirula • so should the 
spiniferous coil or open spire, represented by the flesh-spicule 
of Suberites spinispirulifer (PI. XXVIII. fig. 7), whose spines 
cover the spiral shaft uniformly—that is, without an y spiral 
arrangement. 
In noticing the transition of the stellate to the spinispirula 
in Vioa Johnstonii , Schmidt (Spongien d. atlant. Gebietes, 
p. 5) alludes to his Spirastrella cunctatrix and Chondrilla 
phyllodes. The former was 11 violet or reddish,” and the latter 
“ violet-brown ” in colour, together with identical spiculation ; 
but, from the spinispirula (flesh-spicule) in the latter being a 
little shorter and its consistence gelatinous, especially in 
