378 Reports and Proceedings— 
been injected into the dyke, no such explanation is sufficient in 
the case of the composite dykes of the second class, to which the 
examples cited from Arran belong. 
That the association of two totally different rocks in the same 
dyke is not accidental, the numerous and varied examples at 
Tormore sufficiently prove. Where, as in these cases, we find that 
there is the greatest dissimilarity between both the crystals and the 
glassy groundmass of the two rocks, it is clear that the differentiation 
has taken place in the magma, prior to its injection into the dykes, 
and before the work of crystallization had commenced. The physical 
causes which have been suggested to account for such differentiation 
in a fluid mixture of silicates are discussed. 
2. “Notes on an Intrusive Sheet of Diabase and Associated Rocks 
at Robin Hood, near Bassenthwaite.” By J. Postlethwaite, Hsq., 
The positions of the outcrops of the igneous rock are described, 
and a grit-band is recorded as running parallel to the diabase. The 
diabase, and vein-stuff associated with it, have furnished antimony, 
lead, copper, and arsenic; and the same ores, with the exception of 
the last two, are also found in minute grains in the grit. Analyses 
of the grit and diabase, made by Messrs. Hellon and Brockbank, 
are given. Prof. Bonney has examined slides submitted by the 
author, and has allowed the use of his notes in the paper. The 
igneous rock has produced slight metamorphism in the surrounding 
rocks of the Skiddaw Slates. 
3. “On Two Dinosaurian Teeth from Aylesbury.” By RB. 
Lydekker, Esq., B.A., F.G.S. ; 
Two teeth from the neighbourhood of Aylesbury, believed to be 
of Portlandian age, may be referred to the same species as is a tooth 
figured by De La Moussay from the Portlandian of Boulogne. The 
Aylesbury teeth are described in the paper, and the nature of the 
animal which possessed them is discussed. 
4, ‘Ona New Plesiosaur trom the Waipara River, New Zealand.” 
By Capt. F. W. Hutton, F.R.S., F.G-S. 
This specimen was shortly described by Sir James Hector in 18783. 
The author considers it more prudent to follow Mr. Lydekker in 
referring all the known New Zealand Cretaceous Sauropterygians 
with which he is acquainted to Leidy’s genus Cimoliosaurus, and he 
therefore describes this form as a new species of that genus. 
d. ‘Observations on the Affinities of the Genus Astrocenia.” By 
Robert F. Tomes, Esq. F.G.S. 
Researches recently made by the author relative to the structure 
of certain undoubted Astrocenie of the Gosau beds, having for their 
primary object the better understanding of the supposed species of 
the genus obtained from the Glamorganshire conglomerate, have 
been productive of results which will render a complete modification 
in the classificatory position of the genus imperative. 
The author gives a new definition of the genus, in which he does 
not at present include any species of an earlier date than the Cre- 
taceous period, all the so-called Jurassic Astrocenie being referable 
to other and quite distinct genera. 
