On the Lower Secondai-y Rocks of England. 381 



apophysis ; ischium receiving the abutment of the last two pairs of 

 sacral vertebrae. 



The form of the anterior aperture of the pelvis is oval, with the 

 sides broken by a slight angle at the middle, and the small end 

 encroached upon by the slight angular prominence of the symphysis 

 pubis. The long diameter is 11 inches (from the fore-end of the 

 first sacral vertebra), the transverse diameter is 10 inches. The 

 fore-half of this aperture is bounded by the first sacral vertebra 

 exclusively, at the middle by its centrum, at the sides by its ribs ; 

 the hind-half of the aperture is bounded by the pubic bones. From 

 the penultimate sacral vertebra to the symphysis pubis it measures 

 5 inches. 



The outlet of the pelvis is of a semielliptic form, 9 inches in 

 transverse, and 4 inches in the opposite diameter. Original trans- 

 mitted by Mr. Bain from East Brink River, South Africa. 



Crocodilia (.?). Genus Maasospondylus, Ow. (Gr. naavtov, 

 longer; crnoylvKos, vertebra). — The author exhibited diagrams, and 

 pointed out the characters on which he had founded (in the Cata- 

 logue of Fossil Remains of the Museum of the College of Surgeons) 

 the genus Massospondylus, exemplified by the M. carinatus. 



Genxxs Pachyspondylus, Ow. (Gr. Tragi's, thick; oTrovhvXos, ver- 

 tebra). — The fossils exemplifying this genus form part of the same 

 collection, obtained by Messrs. Orpen from sandstones of the Dra- 

 kenberg range of hills. South Africa, and presented to the College 

 of Surgeons. 



2. " On the South-easterly Attenuation of the Lower Secondary 

 Rocks of England, and the probable depth of the Coal-formation 

 under Oxford and Northamptonshire." By Edward Hull, Esq., 

 A.B., F.G.S. 



By a series of comparative sections, made by actual admeasure- 

 ments by the officers of the Geological Survey, it was shown that all 

 the Lower Secondary formations attain their greatest development 

 towards the north-west of England, and, on the other hand, they 

 become attenuated, and in some cases actually die out, in the oppo- 

 site direction. For example, it was shown that the Bunter Sand- 

 stone in Cheshire reaches a thickness of 2000 feet, in Staffordshire 

 600, and in East Warwickshire is absent ; and a similar law of 

 south-easterly attenuation was shown to maintain in the case of the 

 Keuper, Lias, Inferior Oolite, and lower zone of the Great Oolite. 



It was shown that the ui)per zone of the Great Oolite (the White 

 and Grey Limestones of Wilts, Oxford, Lincoln, and Yorkshire) 

 forms the first exception to the law ; and from the fact of its occur- 

 rence in the Bas-Boulonnais below the Chalk, and resting on car- 

 boniferous rocks, the author inferred that it extends more or less 

 uninterruptedly from England to France and Belgium, and south- 

 ward to Air. Godwin-Austen's palaeozoic axis. The cause of this 

 superior degree of persistency was referred to the organic, as distinct 

 from the sedimentary nature of the formation, and its accumulation 

 (like the White Chalk) on a decj) sea-bed by the agency of Mol- 

 luscs, Corals, and Foraminifcra. 



