— 58 — 
which also form irregular furrows on the surface of the skeleton, 
beneath the dermal layer. By the careful removal of the 
matrix, the dermal laminae can be seen in places on the 
surface of the sponge which they appear to have completely 
covered and the differently-shaped laminae are present in the 
same individual sponge. A comparison with the type spe- 
cimens show such a close agreement both of the mesh and 
dermal spicules that there can hardly be a doubt, but that 
these Horstead spicules belong to the same species. P. sqgua- 
mosa is from the Upper Chalk of Ahlten in Hanover. 
Genus Ragadinia, Zittel 1878. 
Ragadinia annulata n. sp. 
(Plate IV, figs. 24—30. Plate V. figs. 1—4.) 
g 
Spicules of the mesh (Pl. V, figs. 1—4) minute, irregularly 
four-armed; frequently one arm truncated and having a round 
knob at its termination; the other arms having a single 
prominent ring-shaped expansion a short distance from the 
centre, but otherwise with smooth surfaces. These arms bi- 
furcate and terminate in irregular twig-like extensions, which 
interlock with each other to form the mesh. Length of spicular 
arms varying from 0,27mm. to 0,74mm.; and in thickness 
between 0,067mm., and 0,135mm. Surface spicules (Pl. IV, 
figs. 24—30) composed of spicular discs, more or less lobed 
and branched, and having a rudimentary shaft. These discs 
vary in diameter between 0,675mm., and 1,26mm. 
The mesh spicules of this species are very distinctly 
marked off from any other of the allied forms by the peculiar 
ring-shaped swelling with which the arms are furnished. One 
arm of the spicule extends but a short distance from the 
central point and then expands into a prominent rounded knob; 
the other three arms radiate irregularly from the centre, near 
which each has the ring-shaped swelling, and then rapidly 
