116 Mr. H. J. Carter on the Genus Rossella. 
the body and their heads respectively (fig. 4, bb); shaft smooth, 
or only microtuberculate over the imbedded end; arms more 
or less flexuous, fine-pointed, parting from the head of the 
shaft at different angles, covered almost throughout with 
minute spines, closely approximated, amongst which, here and 
there, is a much larger spine, curved and inclined outwards or 
from the head of the shaft; average largest size 2 to 3-12ths 
by 5-1800ths of an inch in the greatest diameters, both for 
the arms and shaft respectively, the former for the most part 
longer than the latter. 3B. Structural spicules (that is, of the 
body or wall) of three forms, viz. :—4. Nail-like or crucially 
headed, much like that last described, but with the shaft shorter 
and the arms longer; the former vertically placed in the wall 
and the latter spread out horizontally over its external surface, 
so as to support the lattice-like layer of minute sexradiate 
spicules imbedded in the dermal sarcode immediately above 
and the shafts of the veil-spicules beyond ; arms more or less 
curved inwards, so as to render the head of the spicule pro- 
minent or monticular, thus characterizing the surface by a 
number of conical eminences linked together by radiating 
arms. 5. A long linear spicule, nearly straight, fusiform, often 
presenting in the middle two or four tubercles corresponding 
to the ends of the crucial branches of the sexradiate central 
canal, terminating in spined and more or less inflated ex- 
tremities, but otherwise smooth; average largest size 3-12ths 
by 2-1800ths of an inch in its greatest diameters ; situated on 
the inner side of the wall chiefly, where it forms, together 
with minute sexradiates and flesh-spicules, the surface of the 
concavity. 6. Sexradiates, of different sizes, with arms of 
equal length, spined and pomted, chiefly composing the lattice- 
like structure, which, in the way above stated, covers the 
whole of the dermal surface with quadrangular interstices 
from 1-300th to 1-150th of an inch in diameter. c. Flesh- 
spicules of four rosette-forms, chiefly situated in the surface- 
layer of the cavity:—7. Sexradiate rosette with smooth 
pointed arms of equal length (‘ Annals,’ 1873, vol. xii. pl. xi. 
fig. 1). 8. Sexradiate rosette with short arms and double 
rays (7b. fig. 3). 9. Very minute sexradiate rosette with 
numerous straight capitate rays (PI. X. fig. 7,4). 10. Sex- 
radiate rosette with thick, sparsely spined arms (fig. 6, a), 
whose inflated ends support four or more indistinctly capitate 
rays (fig. 6, 6 c): rays microspined, thick at first, then becoming 
finely attenuated and terminating in a hardly perceptible capi- 
tate inflation (fig. 6, @); rays at first straight and parallel hke 
the prongs of a dinner-fork, becoming more or less divergent 
towards their extremities (fig. 6); average largest size of the 
