Book Notice. 251 



militate against the employment of biological phenomena as 

 absolute indices of physical conditions. The question may 

 always be raised, when it is found that a species or fauna 

 becomes extinct about a certain horizon, did the species or 

 fauna become extinct really or locally ? Did it migrate to 

 some locality, and flourish long after it had ceased to exist at 

 its original locality ? In conclusion, in working out life zones 

 of a series of rocks, the following facts may be useful as 

 aphorisms. In a succession of strata, w^here muddy con- 

 ditions succeeded a pure limestone phase, it is natural to 

 expect a change of fauna, but where tw^o shales or limestone 

 contain dissimilar faunas, they are probably not contemporan- 

 eous. Faunas of different bathymetric zones may be con- 

 temporaneous, though they are dissimilar. 



The period of time during which a species or fauna may 

 survive at any locality depends entirely on the conditions of 

 environment. Hence conditions will determine the vertical 

 extent of rocks characterised by a zonal group or species. 



Dissimilar faunas may be contemporaneous. To take an 

 example, the fresh water and marine fauna of the Coal 

 Measures must have been in existence contemporaneously in 

 different areas, though they never occur in the same bed. 



Hence it is rarely safe to rely on single species, and the 

 larger the group used to denote a zone, the more accurate will 

 be the result. It is the association of a number of species at a 

 horizon which I consider to be the important thing in zoning 

 the Carboniferous rocks. And the first appearance of such an 

 association of forms is obviously the most important horizon^ 

 as it points to the establishment of a new set of conditions. 



— 



A Naturalist in Tasmania, by Geoffrey Smith. Oxford : Clarendon 

 Press. 151 pp., 7/6 net. 



With the aid of a substantial grant from the British Association, 

 Mr. Smith paid a six months' visit to Tasmania, principally to 

 study the fresh-water life of the island, and particularly that strange 

 creature, the Mountain Shrimp, which seems to be a survival from 

 Carboniferous times. During his sojourn on the island, the author made 

 many interesting notes in reference to the fauna, flora, history and an- 

 thropology of Tasmania, which are now presented in the form of a very in- 

 teresting narrative. To the student of geographical distribution the volume 

 is essential. There are evidences of parts of the book having been hurriedly, 

 if not carelessly written. On page 60 the word ' cushion ' appears half a 

 dozen times quite close together, and other words are unnecessarily 

 repeated. We made a hasty reference to the page said to contain a drawing 

 of ' the Devil by Mr. Goodchild,' only to find Savcophilus ursinus, with 

 neither hoof, horn, nor forked tail. 



1909 July I. 



