NOTICES OF BOOKS. xliii 



weighted with stratigraphical considerations. The author's name is 

 itself a guarantee of thoroughness and scholarly research. His Museum 

 catalogue, and the miscellaneous articles which in the intervals of more 

 serious work have fallen from his pen, led us to expect a really good 

 book, and in this we have not been disappointed. 



Four hundred and ten pages of the work are devoted to a systematic 

 treatment of the vertebrata taken in ascending order of classification ; 

 and of the thirty pages which remain, eight are given over to 

 an " Introduction " dealing in a comprehensive manner with certain 

 broad principles, and the concluding twenty-one to a consideration 

 of " the succession of the vertebrate faunas," the whole closing with a 

 most admirable bibliography arranged on a novel scheme which 

 facilitates reference. In the concluding section of the book the author 

 deals with questions of geographical distribution as bearing on the 

 isolation of continental areas, and upon this, especially as concerning 

 the American continent and supposed isolation since cretaceous times, 

 we cannot altogether follow him, since his theory is in part irreconcilable 

 with facts of distribution of living mammals. 



Among the classificatory systems adopted by the author, we hail 

 with satisfaction those of Cope, and that of the Rhychocephalia by 

 Boulenger ; and it was to have been expected that the fishes would be 

 arranged in accordance with his own recent scheme, fully developed 

 in his British Museum catalogues. We cannot allow to pass unno- 

 ticed, however, his bold persistence in the association of the pteraspid, 

 cephalaspid and pterychthyid forms (with a caution it is true) with the 

 cyclostomi, rendered the more dangerous as it is by the unwarrantable 

 statement, in defining the class, that " it is generally admitted that the 

 existing cyclostomes or marsipobranches are . . . degenerate". Nor 

 can we see sufficient justification for the continued association of the 

 Coccosteids (Arthrodira) with the Dipnoi. As concerning the author's 

 diagnosis of the latter, it is a remarkable fact that neither he nor any 

 other distinguished palaeontologist who has thus far written upon them 

 appear to us to have sufficiently emphasised the really distinctive 

 character of the group, viz., that the fact that " the dentition has always 

 been confined to the inner boneg of the mouth " is the expression of 

 preponderating development of the palatopterygoid over the premaxillo- 

 maxillary arcade, the precise converse of that occurring in all other 

 gnathostomata. And, concerning this, we would point out that 

 from a knowledge of the Stegocephalia our living Urodela would appear 

 to have undergone an essentially similar change (Tylototriton alone 

 excepted), and to be therefore in respect to their jaw apparatus as to 

 their digital skeleton one and all degenerate (a conclusion based on the 

 facts of palaeontology which the study of the living alone would not 

 suggest), and that consequently we may reasonably suspect the existence 

 of premaxillo-maxillary bones in a vestigial condition among the earlier 

 Dipnoi, especially if the arguments of Dollo in defence of a belief in 

 their crossopterygian origin be, as we consider them, sound. 



