238 Reports and Proceedings — Geological Society of London. 



was abraded, l)roken. and chipped along one edge in the same fasliion 

 as the alleged " Eolithic " working ; finally it was stained, marked 

 with glacial striee, and covered witli a thin layer of white silica. 



This implement appears to prove that Palceolithic man lived on 

 the Kentish plateau before or during the deposit of the plateau- 

 gravels, and that the " Eolithic " chipping is not the work of man. 



2. " On the Grouping of some Divisions of Jurassic Time." By 

 S. S. Buckman, Esq., F.G.S. 



The author ai'gues for an arrangement in the division of Jurassic 

 time based upon the zoological phenomena of the Ammonite-fauna. 

 He considers that such time-divisions should be related to the 

 duration of Ammonite families. He divides the Jurassic Period into 

 two epochs — the Eojurassic and the Neojurassic : the former the time 

 when the Ammonite families of the Arietidee and their close ally the 

 Hildoceratidfe were dominant; the latter commencing just upon the 

 extinction of these families, and being the time when the StejDheo- 

 ceratid^ held chief sway. 



The epochs are subdivided into ages, and the ages, again, are divided 

 into hemerae — a hemera being the chronological unit. Reasons are 

 given for the different subdivisions, and for commencing the Eojurassic 

 Period with the ro/Z/brnn's-hemera. 



The Eojurassic Period it is proposed to divide into four ages — the 

 Sinemurian, the Pliensbachian, the Toai'cian, and the Aalenian. 



During the Sinemurian age, whereof the zoological phenomenon is 

 the acme and paracme of the Arietidge, was deposited a part of the 

 Lower Lias, beginning with the zone of Ammonites BucMandi and 

 ending with that of A. oxynotus. This age is divided into the 

 following seven hemeras, stated in ascending order : rotiformis, 

 Gmiiendensis, Birchi, Turneri, ohtusi, stellaris, oxynoti. 



During the Pliensbachian age, marked by the dominance of 

 Deroceratidee and AmaltheidfB, was laid down the rest of the 

 Lower and almost all the Middle Lias. It includes seven hemerse, 

 namely : raricostati, armati, Jamesoni, Yaldani, striati, margaritati, 

 spinati. 



During the Toarcian age, when the Bumorfierics and a part of 

 the Hildoceratidse were prominent, the following strata accumu- 

 lated : a small part of the Middle and the whole of the Upper 

 Lias, the Cotteswold Sands, the Midford Sands, and a portion of the 

 Yeovil Sands. There are ten hemeree : acuti, falciferi, bifrontis, 

 Lillice, variabilis, striatuli, Stnickmanni, dispansi, Dumortierion, 

 Moorei. 



During the Aalenian age, when there was a preponderance of 

 another portion of the Hildoceratidee which may be known as the 

 Ludwigia-grou-p, and of Hammatoceras, the rest of the Yeovil 

 Sands and a part of the Inferior Oolite were the accumulated 

 deposits. This age is divided into the following six hemeras : 

 Aalensis, opaliniformis, scissi, Murchisonce, Bradfordensis, concavi. 



Part of the Neojurassic division is separated into two ages. 

 During the first, the zoological phenomenon is the acme and 



