330 Reports and Proceedings— 
shell is composed chiefly of oligoclase, but also contains abundant 
included plates of biotite, and over 12 °/, of magnetic iron-ore. It is 
to the presence of the last-mentioned mineral that the zonal portion 
owes its dark colour. By means of a Sonstadt’s solution the oligo- 
clase was isolated and analyzed with the following results :— 
SiO, = 60:99 
Al,O3 = 25°56 
CaO = 4°88 
Na,O =. 7°48 
Loss on ignition = “84 
100°00 
Sp. Gray 520492 
This is the composition of an oligoclase of the formula Ab,An. 
The felspar of the zonal portion is disposed radially, the iron-ore 
radially and concentrically, while the mica appears to obey no fixed 
law of arrangement. 
A synopsis of the literature concerning the occurrence of similar 
concretionary bodies in granite was then given, the following authors 
being referred to:—Leopold v. Buch, Gustav Rose, Allnaud, Char- 
pentier, Jokély, von Andrian, Zirkel, G. W. Hawes, M. de Kronst- 
schoff, J. A. Phillips, vom Rath, Fouqué, Halst, Brogger, and 
Backstrom. 
The conclusion the author arrived at from a consideration of the 
subject was, that concretionary bodies occurring in granite, may, 
according to the mode of arrangement of their constituents, be 
divided into three classes, viz. :— 
1. The concretionary patches of Phillips. 
2. The granospherites of Vogelsang. 
3. The belonospherites of Vogelsang. 
The spheroids from Mullaghderg belong to the last-mentioned 
class. They must be regarded as concretions formed, during the 
consolidation of the granite magma, by a process of zonal and radial 
crystallization around an earlier-formed nucleus. 
2. “On the Skeleton of a Sauropterygian from the Oxford Clay, 
near Bedford.” By R. Lydekker, Esq., B.A., F.G.S. 
A description was given of a considerable portion of the skeleton 
of a Sauropterygian from the Oxford Clay of Kempston, consisting 
of several upper teeth, most of the mandible (of which the symphy- 
sial region is entire), a considerable number of vertebra mainly 
from the “pectoral” and dorsal regions, the greater portion of the 
two pelvic, and fragments of the pectoral limbs, and a considerable 
proportion of the pectoral and pelvic girdles. 'These remains were 
referred to Plesiosaurus philarchus, Seeley, and the various parts 
described in detail. 
The author discussed the advisability of retaining the forms de- 
scribed by various generic names by Professor Seeley, under the 
name of Plesiosaurus, and stated his intention of employing the 
latter term in its widest sense for the present. With this definition, 
the form under consideration was shown to present characters inter- 
1 By difference. 
