Reviews — Yorkshire Type Ammonites. 429 



figured. The ore-deposits of Sulitelma occur in highly meta- 

 morphosed rocks of Cambrian and Silurian age in close association 

 ■with amphibolites (sheared gabbros). The origin of the ore-bodies 

 is still a matter of controversy, Vogt considering them to be derived 

 directly from the gabbro magma, while Sjogren holds that they have 

 been formed metasomatically by the action of aqueous solutions. 



IX. — Yorkshire Type Ammonites. Edited by S. S. Buckman. 



Photographs by J". W. Tutcheh. Part XVIII. London: Wesley 



and Son. March, 1919. 

 rilHIS part completes the second volume of this most useful 

 JL publication. Accordingly it furnishes a table of contents, the 

 precise dates of publication of each page and plate, zoological and 

 chronological lists of the genera dealt with, an index, and other 

 necessary matter. It is noted that the first two volumes contain 

 163 plates, illustrating 137 species. There are still some type- 

 ammonites of Yorkshire to be redescribed, but it is proposed now to 

 extend the scope of the work by including type-specimens of Jurassic 

 ammonites from other localities in the British Isles. The price will 

 be raised to 10s. net for each part, consisting of 10 to 12 plates and 

 text, but should circumstances permit the number of plates may be 

 increased. 



The chief species figured in this part are: Ammonites impendens, 

 Young & Bird, referred to Arietites ; Ammonites longavus, Bean, 

 cit. Leckenby, which gives rise to two new genera, the lectotype 

 becoming Longceviceras longcevum and the other syntypes becoming 

 Pseudocadoeeras boreale. Supplementary plates are given of Gagati- 

 ceras funiculatum, Beaniceras costatum, and Fimbrilytoceras fimbriatum. 



X. — Recent Advances in Rhodesian Geology. By H. B. Maufe. 

 Pres. Add. Proc. Geol. Soc. S. Africa, 1919, pp. xxi-xxxvi. 



IX this address Mr. -Maufe gives a comprehensive general account 

 of the geology of Rhodesia, as worked out by himself and his 

 colleagues on the Geological Survey. The subject is treated mainly 

 from the stratigraphical point of view, and the petrographical 

 characters and probable origin of the leading rock-types are 

 discussed. The outstanding feature of Rhodesian geology is the 

 enormous preponderance of the oldest systems, composed of 

 crystalline schists and intrusive bathyliths, which occupy most of 

 the country, while newer formations are scantily developed. Hence 

 there are many gaps in the geological history of the country. 

 Special attention is drawn to the curious problem of the origin of 

 certain types of banded ironstones, which have been shown to be 

 altered felsites, while it is also believed that many of the so-called 

 conglomerates are really of intrusive igneous origin, the " pebbles " 

 being lenticular masses of rather more basic composition derived 

 from the same magma as the base. A noteworthy feature of the 

 older series is the enormous volume of basic igneous rock, now 

 represented by epidiorite, and perhaps exceeding in magnitude even 



