204 Dr. G. J. Hinde on Fossil Calcispongie. 
same locality; and it seems very probable that the majority 
of the Pharetrones possessed a similar dermal layer, which, 
on account of the minute size of the spicules and the un- 
favourable condition of preservation, has not been hitherto 
noticed. 
EXPLANATION OF THE PLATES. 
PrAmE XC 
Fig. 1. Verticillites D’ Orbigny?, n. sp., natural size. 
Fig. 2. The same, natural size. 
Fig. 8. Corynella socialis, n. sp., natural size. 
Fig. 4. Corynella rugosa, n. sp., natural size. 
Fig. 4a. The same, showing the summit, with the cloacal aperture. 
Fig. 5. Sestrostomella clavata, n. sp., natural size. 
Fig. 6. Sestrostomella rugosa, n. sp., natural size. 
Fig. 7. Fragment of the outer surface of Verticilhites D Orbigny?, showing 
the apertures in the wall, and the disposition of the large dermal 
spicules. xX 56. 
Fig. 8. Fragment of the interior surface of the wall of V« erticillites d’ Or- 
, bignyt, showing the arrangement of the minute triradiate 
spicules composing the fibre. X 56. 
PuatE XI. 
(Figs. 1-24. Detached spicules of Verticillites D Orbigny?.) 
Dermal 'spicule. Sagittal quadriradiate, with the lateral or paired 
rays curved away from the basal ray. 
The same. The lateral rays of this specimen are unequal in 
length, probably owing to the erosion of the shorter ray by 
fossilization. 
Fig. 1. 
Fig. 
i 
Fig. 8. Dermal spicule. Sagittal quadriradiate, with straight lateral rays. 
Fig. 4. Dermal spicule. Sagittal quadriradiate, with the lateral rays 
straight and in a straight line with each other. 
Fig. 5. Dermal spicule. Sagittal quadriradiate, with the lateral rays 
curved towards the basal ray. : 
Fig. 6. The same. 
7 
The basal ray more elongated than in the preceding. 
Fig. 7. The same. 
Quadrirvadiate, with the three facial rays nearly equal 
in length; the lateral rays are slightly curved towards the 
basal ray. 
Fig. 8. The same. Sagittal quadriradiate, showing the apical ray. 
Figs. 9-18. Small forms of dermal spicules ; all triradiates, with the rays 
unequal in length. 
Fig. 14. Spicule of the fibre. Sagittal triradiate, with straight lateral 
rays and diminutive basal ray. This form most frequently occurs 
on the interior surface of the sponge-wall. 
Fig. 15. The same. Triradiate, with unequal lateral rays, and the basal 
rays reduced to a small knob-like projection. 
Figs. 16, 17. Dermal spicules. Sagittal triradiates, showing transitional 
forms between the dermal spicules and those of the fibre. 
Figs. 18-23. Spicules of the fibre. Sagittal triradiates of various dimen- 
sions; the lateral rays mostly curved, so as to conform to the 
Cust ulee of the fibre ; the basal ray reduced to a diminutive 
snob. 
Fig. 24. Dermal spicule. Triradiate with all the rays unequal. 
