142 On Carboniferous Sponges from S8.W. Scotland. 
Fig. 7. The same. Fragment of surface of body, showing, a a, “nail- 
like” spicules 2 situ, and, 6 6, fenestral openings. xX 2. [N.B. 
In this figure the arms, which appear to have been broken off or 
absent, have sunk beneath the surface. | 
Fig. 8. The same. “Nail-like” spicule of the most regular form. xX 3. 
Fig. 9. The same. Lateral view of nail-like spicule, showing the con- 
striction at the fixed ends of the arms respectively. X 3. 
Fig. 10. ? The same. Stelliform nail-like spicule with smooth and tuber- 
cled arms respectively. a, smooth or small form; 4, large, 
matured, or tubercled form. x 3. 
Fig. 11. ? Thesame. Double stelliform nail-like spicule. a, small form ; 
b, large or matured form; cc, stelliform head in a@ and 6 respec- 
tively ; dd, arms respectively: x 3. e, more magnified view of 
head, showing trifurcation of a lateral spine of stelliform head 
and tubercles over central one. 
Fig. 12. ? The same. Simple sexradiate spicule. 
Fig. 18. The same, to show grooving. Magnified view of a few of the 
cord-spicules in situ. Transverse section. a a, two single- grooved 
spicules together, the largest about 3-48ths inch in diameter; 
6, more magnified view of a transverse section of a single- 
erooved cord-spicule ; c, the same of a four-grooved spicule ; d, 
the same of a thirty-two-grooved spicule ; e, lateral view of a 
fragment of the latter. All x 16. 
Fig. 14. The same. Fragments of the siliceous spicule encroached upon 
by calcite subsequently redissolved and leaving excavations. 
a, lateral view of a fragment of a cord-spicule presenting a few 
excavations ; b, end view of a fragment presenting many exca- 
vations, extending to the centre; c, lateral view of a fragment 
rendered shapeless by being fretted out by general excavation. 
Fig. 15. Rhaphidhistia vermiculata, n. sp. ? On a species of Hydractina. 
Upper view. xX 2. 
Fig. 16. The same. Fragment of the Hydractinia, much magnified, to 
show :—a, layer of Rhaphidhistia on, 66, conoid columns and 
reticulate structure of Hydractinia, based on, cc, membranous 
expansion, now lapiditied ; d, truncated fibre of Hydractinia ; e, 
truncated column, showing axial cavity; fff, interstices of 
fibre. 
Fig. 17. The same. Conoid column incipiently bifurcated, much magni- 
fied, to show the absence of the layer of spicules. 
Fig. 18. The same. Conoid column, much magnified, to show presence 
of the layer of spicules. 
Fig. 19, The same. Probable form of entire spicule. 
N.B. The above are all siliceous fossils. 
PLATE X. 
Fig. 1. Pulvillus Thomsonit, n. sp. (Calcareous.) Upper view. a, central 
excavation, presenting the broken ends or transverse sections 
respectively of the spicules (fig. 6). Half the natural size. 
Fig. 2, The same. Verticalsection through the centre, showing :—a, upper 
or large excavation; b, lower or smaller excavation ; c, ? stem 
or pedicle in smaller excavation ; dd, granules of whitish-brown 
calcite, of which the fossil is chiefly composed, presenting more 
or less longitudinal sections of the bundles of spicules, all tend- 
ing to a vertical direction ; eee, heterogeneous sandy material, 
vein-like between the granules in the upper, replaced by white 
