Reviews — Prestwich's Controverted Questions in Geologij. 231 



the beds in which it occurs I refer to it as follows : "The new genus, 

 for which the author proposes the name Plutonia, is only known to 

 occur in these beds. This remarkable fossil is of very large size, 

 equalling, indeed, in this respect Paradoxides Davidis. It is, 

 perhaps, also more nearly allied to the genus Paradoxides than to 

 any other known, but its peculiar character of being covered all 

 over with very strong tubercles, associated with an unusual position 

 for the eye suture, and straight, very long thoracic pleura, is 

 sufficient to stamp it a new and distinct genus." 



It was more fully described by me afterwards in the Quart. Journ. 

 Geol. Soc. vol. xxvii, p. 399, as Plutonia Sedgioickii. One species 

 only has been discovered and no complete specimen. As mentioned 

 above it resembles, in some particulars, the genus Paradoxides ; but 

 I know of no species in that genus which has such wide plur^, or 

 such a pronounced ornamentation on all parts of the body. The 

 pygidium has not been found ; but some fragments which have 

 turned up seem to indicate that it approached more nearly that of 

 Anopolenus than to Paradoxides. Plutonides greatly exceeded in 

 size any specimens of Anopolenus yet discovered, as portions of the 

 body, which I obtained, show that it could not have been less than 

 seven inches across at its greatest width, or one inch wider than the 

 largest Paradoxides found by us at St. David's, now in the Museum 

 of the Geological Society. Its length, however, would evidently be 

 less than Paradoxides, with fewer segments to the thorax. 



le IE V I :h! "vv s. 



I. — Collected Papers on some Controverted Questions op 

 Geology. By Joseph Prestwich, D.C.L. (Oxon), F.E.S., F.G.S. 

 (London : Macmillan & Co., 1895. 8vo, pp. xii and 280.) 



THE book before us consists of a series of articles, the subjects of 

 which have occupied the author's attention during many years, 

 and concerning some, if not all, of which he is more or less at 

 issue with many of his fellow-geologists. "With respect to the 

 main facts of geology," says Professor Prestwich, " we geologists 

 are in general of one opinion, but with respect to the explanation of 

 many of those facts, we hold very divergent opinions." 



Article 1 treats of "The Position of Geology," and is directed 

 against the prevailing school of geologists in this country who hold 

 the doctrine of Uniformity — uniformity of action both in hind and in 

 degree throughout all geological time; and the Continental school 

 who hold uniformity in hind or law, but not uniformity in degree. 



The points touched upon embrace the rate of sedimentation, 

 calculated upon the transporting power of rivers, which are estimated 

 to lower the level of the land one foot in 6000 years, or one thousand 

 feet in 6,000,000 years. The author remarks that the rate might 

 be doubled if the calcareous matters held in solution, as well as 

 the matter held in suspension, were taken into account. Professor 

 Prestwich also objects to a mean rate of elevation of land at 2^ feet 



