Reviews — Prestwictis Geological Text-Book. 83 



We live in an age of change, and in no department have greater 

 changes arisen lately than in that of Biology. The author has 

 brought together in this chapter a series of tables of classification 

 of each group of the animal kingdom ; but as these tables are neces- 

 sarily by various authors, and of very varying dates of publication, 

 from 1868 to 1883, some at least need emendation. 



Thus in the classification of the Mammalia (p. 79) the Seals, 

 (Pinnipedia) have been placed with the Cetacea, whereas they are 

 now universally placed with the Carnivora; and the Sloths, Ant- 

 eaters, and Armadillos (Edentata), have been placed between the 

 Carnivora and Rodentia, whereas they are now placed next the 

 Marsupialia. 



The Proboscidea, Pachydermata, Solipedia, and Euminantia 

 are not so arranged by later zoological writers, but they form one 

 great order, the Ungulata (or hoofed quadrupeds) divided into 

 various sub-orders, as 



Sub- order 1. Hyracoidea (Hyrax) ; 



„ 2. Proboscidea (Elephants) ; 



„ 3. Amblypoda (Dinoceras, etc.) ; 



„ 4. Perissodactyla (Tapirs, Rhinoceroses, Horses) ; 



„ 5. Artiodactyla (Pigs, Deer, Oxen, and Sheep). 



Happily these and other needful modifications can be made in 

 Volume II., which deals with the Life-history of the Earth, and is 

 not yet published. 



On p. 69 the Myriopoda have accidentally got between the 

 Decapoda and the Cirripedia ; and on p. 68 Entomostraca and 

 Malacostraca seem of equal classificatory value with Insecta, 

 the word Crustacea, which should be the leading one, being sub- 

 ordinated. The Arachnida and Myriopoda should not be bracketed 

 together, they are really widely separated groups. Neither 

 should the Marsipobranchii and the Pharyngobranchii be 

 bracketed together (p. 76). The first embraces the "Hag-fish" 

 (Myxine) and " Lamprey " (Petromyzon) ; the second a single form 

 the "Lancelet" (Amphioxus) , so anomalous as to be by some naturalists 

 relegated to a separate class ! 



It is, therefore, misleading to the student to bracket these 

 two together with the remark (after " no fossil forms known ") 

 " ? Conodonts " ; for if the curious little microscopic bodies called 

 " Conodonts " met with by Pander in Russia and by Hinde in the 

 Cambro-Silurian and Devonian rocks of North America, are fish- 

 teeth, which is very doubtful, 1 they must have belonged to the " Hag- 

 fish " (Myxine), and could have nothing to do with Amphioxus, which 

 is destitute of teeth or any other hard organs whatever. 



But to pass on to the question [Chapter VI. (p. 82)] how 

 "Sedimentary strata are formed by river and sea erosion." Com- 

 mencing in the truly philosophical ' Lyellian ' and ' Darwinian ' 

 style to argue from the known to the unknown, we find the author 

 teaching his students " to study the effects of the agencies at present 



1 See Quart. Journ. Geol. Soc. vol. xxxv. 1879, pp. 351-368, plates xv.-xvii. 

 Compare these with the odontophore of certain mollusca, Strombus, Cassis, Triton, etc. 



