428 Reports and Proceedings — Geological Society of London. 



■which the indices of two successive zones are found to overlap one 

 another are referred to as * horizon a, p, 7,' etc. 



The detailed stratigraphical portion of the paper deals with all 

 the important sections and isolated exposures in the Bristol area : — 

 The Avon section, the Sodbury section, the Farland area, the 

 Tytherington section, the Clevedon and Portishead area, isolated 

 exposures, and the Backwell-Wrington mass. In each case there 

 is given (1) a description of the position at which each zone or sub- 

 zone is exposed and of its lithology ; (2) a list of the corals and 

 brachiopods found in the zone or sub-zone, with notes on their 

 abundance ; (3) a comparison with the same horizon in other parts 

 of the Bristol area, and notes on the peculiarities of the section 

 under discussion. In dealing with the Avon section an analysis is 

 given of Stoddart's paper, and reference is made to his collection. 

 The details of this portion of the paper are next summed up in 

 tables and discussions of the ranges and maxima of the corals and 

 brachiopods within the Bristol area. This is followed by a com- 

 parison of the last-named area with that of the Mendips, resulting 

 in the conclusion that, when allowance is made for small variations 

 (which are tabulated) the paleeontological sequence agrees remarkably 

 in the two ai'eas. 



The author next gives a summary of M. Lohest's discussion of 

 the parallelism of the Belgian sequence with that of the Avon 

 section, and adopts the Belgian divisions of Tournasian and Visean 

 for the lower and upper parts of the Carboniferous Limestone. 

 A comparison is also instituted with M. Mourlon's grouping, and it 

 is remarked that the Brachiopods mentioned by M. Mourlon and 

 Professor Dewalque occur in the same order in the Bristol area as 

 in Belgium, and are correspondingly characteristic of the beds. 

 The author claims that in the area with which he deals, his table 

 of ranges is sufficient to enable any worker to zone any exposure 

 with a considerable degree of accuracy. In conclusion, notes are 

 given on all the important species and circuli dealt with ; and 

 descriptions of a number of new species, circuli, and mutations. 



2. " On a small Plesiosaunis Skeleton from the White Lias of 

 Westbury-on-Severn." By Wintour Frederick G wiunell, Esq., F.G.S. 



The remains described were found on the beach, and had evidently 

 recently fallen from the cliff above, which is made up of the Upper 

 Ehgetic beds, including the Estheria-hed and the White Lias Lime- 

 stone. The matrix of the specimen corresponds with the White 

 Lias in colour, texture, and material, and it is similarly traversed 

 by fissures often coated with dendrites. The remains include more 

 than twenty small dorsal vertebrae, with spinous and transverse 

 processes, lying in natural sequence. A pseudomorph of the spinal 

 cord in calcite occurs also in position. Several slender ribs, and 

 indications of other bones, probably from the pectoral or pelvic 

 arches, also occur in the slab, but are not yet worked out. Hitherto 

 only single vertebrge or fragmentary bones of Plesiosaunis have been 

 recorded from this horizon in Britain. At present it has not been 

 found possible to assign the fossil to any existing species. 



