236 Reports and Proceedings — 



of the side of the centrum. Several other peculiarities were also 

 pointed out. 



The paper concluded with notes on other vertehrse of similar 

 character from Tilgate and Brook, and attention was called to a 

 Crocodilian cervical vertebra with the procoelian cup from the Purbeck 

 beds. 



5. "On a Sacrum, apparently indicating a new type of Bird 

 {Ornithodesmus cluniculus, Seeley), from the "Wealden of Brook." By 

 Prof. H. G. Seeley, F.R.S., P.G.S. 



After some remarks on the characters of the sacrum in Birds, 

 Ornithosauria, and Dinosauria, the author proceeded to describe a 

 sacrum composed of six vertebrae in the Fox collection, now at the 

 British Museum, and then to compare the fossil with the corresponding 

 bones of the three groups named. The resemblance to the Dinosaurian 

 and Ornithosaurian sacral vertebrae was less than those which connected 

 the fossil with birds. Prom the hitter it was distinguished by the 

 smaller number of vertebrae in the sacrum, the absence of sacral 

 recesses for the lobes of the kidneys, and the form of the articular 

 face of the first sacral vertebra. But the small number of sacral 

 vertebrae in Areh(Bopteryx, the want of renal recesses in Ichthyornis, 

 and the characters of the articulation in the Solan Goose showed 

 that these differences were not essential ; and the author concluded 

 that the fossil belonged to a true Bird, but that it formed a link 

 with lower forms, and approximated more to Dinosaurs than did any 

 other Avian type hitherto described. 



II.— March 23, 1887.— Prof. J. W. Judd, P.R.S., President, in the 

 Chair. — The following communications were read : — 



1. "Notes on the Structures and Relations of some of the older 

 Eocks of Brittany." By T. G. Bonney, D.Sc, LL.D., F.B.S., Pro- 

 fessor of Geology in University College, Loudon, and Fellow of St. 

 John's College, Cambridge. 



These notes are the results of a visit to some of the more interesting 

 geological sections in Brittany, in the autumn of last year. The author 

 is greatly indebted for information to the Rev. E. Hill, who took part 

 in the summer excursion of the Societe Geologique de France, and to 

 Dr. Charles Barrois, who has for long been engaged in investigating 

 the geology of Brittany. 



(1). The author briefly noticed the glaucophane-amphibolites and 

 the associated schists of the He de Groix, which have been already 

 admirably described by Dr. C. Barrois. He considered the evidence 

 to be on the whole in favour of the view that the former were originally 

 igneous rocks intrusive in the latter, but modified by subsequent 

 pressure (the murks of which are very conspicuous in the schists), and 

 by mineral change, which probably produced the glaucophane, the 

 garnets being anterior to the mechanical disturbance. 



(2). The next part of the paper treated of sections in the district 

 about Quimperle. Cases were cited of granite, modified by pressure 

 so as to result in a gneissoid rock, and of banded gneisses also modified 

 by subsequent pressure, but, in the author's opinion, indubitably 

 banded gneisses anterior to the mechanical disturbance, and exhibiting 



