242 Geological Society. 



rostris, and Z. longirostris ; but it is probable that each of these really 

 belongs to a distinct genus — the first to Ziphius, the second to Cho- 

 neziphius, and the last to the author's genus Belemno ziphius. More 

 recently M. Gervais has established anew species — Ziphius Becanii 

 — from a specimen formerly considered to belong to Z. longirostris ; 

 and this species, with that described in this paper, and Professor 

 Owen's M^. species, were also considered referable to Belemno- 

 ziphius. 



Besides the foregoing conclusions respecting the affinities of the 

 fossil Rhynchoceti, Professor Huxley discussed the relations of the 

 recent genera and species belonging to the same group, including 

 the cetacean of Aresquiers, which was considered by Gervais to 

 belong to the genus Ziphius. He exhibited these relations in a 

 tabular form, and concluded by stating that he had arrived at the 

 following results : — 



1. Unless the cetacean of Aresquiers be identical with Ziphius 

 cavirostris, all the Ziphii of Cuvier belong to Cetacea generally 

 distinct from those now living. 



2. If the cetacean of Aresquiers be identical with Ziphius caviros- 

 tris, it is not certain that the latter is truly fossil ; nor, if it be so, 

 have we any knowledge of its stratigraphical position. 



3. Of the certainly fossil Ziphii, the stratigraphical position of 

 Belemno ziphius longirostris is unknown ; but all the other species of 

 that genus, and Choneziphius planirostris, are derived from the 

 English or Antwerp Crag, and are not known to occur out of it. 



4. So that at present we are justified in regarding Belemno ziphius 

 and Choneziphius as true Crag Mammals. 



June 8, 1864.— W. J. Hamilton, Esq., President, 

 in the Chair. 



The following communications were read : — 



1. " On the Rhaetic Beds and White Lias of Western and Central 

 Somerset, and on the Discovery of a new Fossil Mammal in the Grey 

 Marlstones beneath the Bone-bed." By W. Boyd Dawkins, Esq., 

 B.A., F.G.S. 



After describing the sections in the district, and showing the 

 pabeontological relations of the White Lias to the Avicula contorta 

 series and the zone of Ammonites planorbis, the author enunciated 

 the following conclusions : — (1) That the true position of the White 

 Lias is immediately above the Avicula contorta zone of Dr. Wright, 

 and at the base of the Lower Lias shales ; (2) that it is entirely 

 distinct from the Rhaetic beds, lithologically and palaeontologically ; 

 and (3) from the discovery of Rhsetic fossils in the Grey Marls 

 below the Bone-bed, that the latter belong to the Rhsetic formation. 

 He then proceeded to describe a two-fanged mammalian tooth, which 

 he had found in the Grey Marlstones below the Bone-bed, and 

 which he considered to be the analogue of the trenchant four- 

 ridged premolar of Hypsiprymnus, of the section to which H. Hun- 

 teri belongs. Until additional remains be found, its affinities to 



