Revieivs — Dr. 8iemivachki on Ammonites. 325 



Some interesting facts, throwing light on the origin of the 

 Dwyka, have been obtained by the Commission. The most important 

 is the discovery of undoubted scratched stones, resembling true 

 glaciated pebbles; a large boulder of granite, 10 feet by 8 feet in 

 section, was found \y'\ng in the Dwyka in the poort, where the 

 Witteberg Eiver cuts across the Dwyka ridge, soutli of Lainsberg. 

 The pebbles consist of several varieties of granite, several kinds of 

 more basic i(;neous rocks, sandstones, quartzites, argiUaceous and 

 calcareous rocks, and vein quartz. There are distinct bedding planes 

 in the I'ock, and the bedding is everywhere conformable to that of 

 the quartzites of the underlying Witteberg Group. 



Extensive superficial deposits, probably in most cases of recent 

 origin, are mapped in several localities. The most interesting of 

 these are the sand dunes on the shores of False and Table Bays and 

 over large areas in the Malmesbury district. In some places the 

 entire mass of the dunes has been converted into a more or less 

 compact sandstone or limestone, that at Saldanha Bay being quarried 

 as a building stone. These deposits have sometimes been taken as 

 of Tertiary age, but the occurrence in them of recent shells, often of 

 terrestrial genera mingled with bones of rhinoceros, elephant, etc., 

 points to their recent origin. Walcot Gibson. 



Memoirs of the Geological Survey. 



III. — The Water Supply of Sussex from Underground Sources- 

 By William Whitaker, F.R.S., and Clement Eeid, F.L.S., 

 F.G.S. 8vo; pp. iv, 123. (London : printed for H.M. Stationery 

 Office, 1899. Price 3s.) 



MR. WHITAKER, more than any other member of the Geological 

 Survey, devoted attention during his long official career to the 

 important applications of geology to questions of water supply. 

 Now that he has retired from the Survey he has been good enough 

 (as the Director-General points out) to assist Mr. Reid in arranging 

 the numerous records of well-sections, which form the bulk of the 

 present Memoir. The work, in fact, contains all information which 

 could be obtained concerning the well-sinkings and borings in 

 Sussex, with analyses of many of the waters, and a brief intro- 

 ductory account of the geological formations met with in the county. 

 It cannot fail to be of great practical value. 



Descriptive Monograph of the Ammonite genus Perisphinctes. 



IV. MONOGRAPHTSCHE BesOHREIBUNG DER AmMONITENGATTUNG 



Perisphinctes. By Dr. Jos. von Siemiradzki. Paleeonto- 

 graphica, Bd. xlv (1899), pp. 69-352, pis. xx-xxvii. 



rllHE Ammonite genus Perisphinctes, founded by Waagen in 1869 

 i. as rt subgenus of Stephanoceras, and shortly afterwards raised 

 to generic rank by Neumayr, Zittel, and Waagen himself, has now 

 become so large that any atteuipt to classify the forms which have 

 been included in it is not only a difficult task, but entails a vast 



