380 Reports &, Proceedings — Geological Society of London. 



symphysis of the jaw, only the outer paired longitudinal series 

 extending a little farther back over the rami. There are from 

 three to five longitudinal series, each of five or six teeth of the 

 ordinary Climaxodus type, covering the greater part of the sym- 

 physis ; and the flanking paired series, which extends farther back, 

 comprises more depressed teeth, in which the cutting-edge forms a 

 low blunt ridge. The two jaws are nearly similar; but, as in 

 Janassa, the upper seems to have been slightly wider than the lower 

 jaw. The teeth rapidly increase in size backwards, also as in 

 Janassa, but they must have been all retained in the mouth 

 throughout life; while in Janassa only a single transverse row 

 would be in function at one time, the older teeth being thrust 

 beneath to form a supporting base. Climaxodus and Janassa are 

 thus two distinct genera. These Petalodonts are especially note- 

 worthy among the Elasmobranchii, because during the greater part 

 of the life of each individual there cannot have been more than six 

 or eight teeth in succession, a condition remarkably different from 

 ordinary sharks and skates in which the successional teeth are always 

 very numerous and rapidly replaced. The same limited tooth- 

 succession is to be observed in the Carboniferous Cochliodontidae, 

 and perhaps also in the contemporaneous Psammodontidse. Most of 

 the teeth of Climaxodus are also interesting as showing a restricted 

 area of highly vascular dentine much resembling a tritor in the 

 dental plate of an ordinary Chimseroid. This character in 

 Elasmobranch teeth which are peculiar for their slow and scanty 

 succession, may have some special significance in connexion with the 

 origin of the Chimseroids. 



2. " A New Theory of Transportation by Ice : the Raised Marine 

 Muds of South Victoria Land (Antarctica)." By Frank Debenham, 

 B.A., B.Sc, F.G.S. 



A series of deposits of marine muds are found on the surface of 

 floating "land-ice" in the deep bays of Boss Sea (Antarctica). 

 Similar deposits are also found on land up to a height of 200 feet, in 

 some cases on old ice, in other cases on moraine. The deposits are 

 briefly described, and former theories concerning them are discussed. 



A new theory is put forward, prefaced by an account of the nature 

 of the typical ice-sheet which bears them. The upper surface of 

 the sheet is known to suffer a net annual decrease, and evidence is 

 given to show that the lower surface has a net increase by freezing 

 from below. 



The theory is that the sheet will freeze to the bottom in severe 

 seasons, and enclose portions of the sea-floor. Owing to the method 

 of growth of the sheet by increments from below, the enclosed 

 portions will ultimately appear on the surface, thus being raised 

 vertically as well as translated horizontally. 



The application of the theory to other localities is briefly sketched, 

 with especial reference to the shelly moraines of Spitsbergen and the 

 shelly drifts of the glacial deposits of Great Britain. The general 

 results of such a method of transportation are shown to be the 

 raising of marine deposits above their initial level, the preservation 

 of the organisms, the deposition of small patches of muds with 



