322 Reports and Proceedings— 
at a gentle angle, and gradually fade into the continental “ massif.” 
M. de Lapparent is a thorough believer in the fluidity of the 
interior nucleus, and maintains that the weakness inherent in the 
steep side of the chain affords an opportunity for the escape of the 
fluid matter as volcanic ejectamenta. Perhaps, after all, it is not 
easy to conceive a theory which shall meet every case, and some 
might be disposed to think that the author takes too little notice of 
such immense accumulations of ejected matter unconnected with any 
definite chain, such as may be seen on a large scale in Iceland and 
in America. No doubt he claims that the roots of his volcanos 
shall be near water, but he says nothing of the important part which 
steam must play, both chemically and dynamically, as an agent in 
effecting extravasations on the surface. W. H. H. 
7 PORTS) AND 2 2OCh a DE eo 
Gronogrcat Soctety or Lonpon. 
I.—May 12, 1880.—Robert Etheridge, Esq., F.R.S., President, in 
the Chair.—The following communications were read :— 
1. “On the Structure and Affinities of the Genus Protospongia, 
Salter.” By W. J. Sollas, Esq., M.A., F.G.S. 
In this paper the author described the character of the Cambrian 
genus Protospongia from the original and other specimens. In Dr. 
Hicks’s specimen the spicules of the sponge show their original form, 
when it is clear that they are not fused together into a continuous 
network; they form a network only by the interlacing of their 
extremities. The spicules are quadriradiate, with the centre raised, so 
that each spicule indicates the outlines of a low four-sided pyramid, 
the centre being at the apex, and the four rays representing the four 
edges of the pyramid. The rays do not diverge at right angles, and 
thus the base of the pyramid is oblong, though this may be due to 
distortion. From some indications the author is inclined to believe 
that a fifth ray may have sprung from the centre of the spicule down- 
wards. ‘The rays of the spicules appear to be cylindrical. The 
spicules are generally of several sizes, the larger ones forming a frame- 
work which is filled in by the smaller forms, the latter being regularly 
arranged, so that the smaller ones fill up the square spaces left between 
the rays of the larger, and thus build up a network of square meshes 
gradually diminishing in size. The sponge-wall seems to have con- 
sisted of more than one layer of spicules. The spicules were probably 
originally siliceous, but now they consist of iron pyrites. 
With regard to the systematic position of Protospongia, the oldest 
known sponge, the author remarks that similar spicules similarly 
arranged are to be met with in the Hexactinellide, the absence of one 
or two rays being not unusual in part of the spicules of true Hexac- 
tinellids. As the spicules are free, he would refer the sponge to 
Zittel’s Lyssakina, which are nearly equivalent to Carter’s Sarco- 
hexactinellida. 
2. “Note on Psephophorus polygonus, von Meyer, a new Type of 
Chelonian Reptile allied to the Leathery Turtles.” By Prof. H. G. 
Seeley, F.R.S., F.G.S. 
