136 Br. B. Bean — Fishes, Living and Fossil. 



ledgment that has hitherto been made of the prime importance of 

 the succession of life in geological time in determining questions 

 both of morphology and of classification. We have before us his 

 new volume on fishes, just issued in the Columbia University 

 Biological Series, which not merely associates the living and fossil 

 forms in its title, but is permeated throughout with a philosophy 

 which no amount of study of existing fishes would suggest. This is 

 as it should be, and we are delighted to welcome a departure which 

 is likely to be followed by many similar essays. 



Ichthyology, of course, does not strictly fall within the province 

 of our pages, but we are especially concerned with the palaeonto- 

 logical basis on which it must rest; and readers of the Geological 

 Magazine will find many features of great interest in this latest 

 contribution from the University, which the late Dr. Newberry's 

 writings have made famous in the annals of Geology and Palaeon- 

 tology. We propose to review the work from the pal aeon tological 

 point of view, referring more particularly to the original matter 

 which Dr. Dean himself has added to his summary of previous 

 research. 



A brief introductory chapter on the adaptation of fishes to life in 

 a watery medium is followed by a table of classification closely 

 resembling that adopted in the British Museum Catalogue of Fossil 

 Fishes. Next comes a second table showing the distribution of 

 fishes in geological time, mainly based on Zittel's well-known 

 " Handbuch." In this, however, a few small errors have escaped 

 correction, notably the extension backwards of the Acipenseroids 

 and Lepidosteoids to the Upper Silurian, the Clupeoids to the Trias, 

 and Pristiophorus to the Trias and Permian. Nor are any undoubted 

 Arthrodira known above the lowest Carboniferous. In fact, in 

 some of these respects the table does not agree with statements in 

 the text further on. 



After these preliminaries Dr. Dean considers the evolution of the 

 structures characteristic of fishes, and again makes numerous 

 references to the facts of palaeontology in their bearing on the 

 subject. This chapter is for the most part admirable and well up to 

 date in every respect, besides containing important new facts con- 

 cerning the fin-structures of the primitive Carboniferous shark, 

 Cladoselache, to our knowledge of which Dr. Dean has already 

 mae'e several contributions. We have only minor faults to find 

 with the author's treatment of the subject. The researches of 

 Jaekel, for instance, now make it doubtful whether the Permian 

 Pleuracanths had more than five branchial arches (p. 16). Fig. 33 

 (p. 39) represents a dorsal fin-spine of the Carboniferous Lepra- 

 canthus, not Hybodus as labelled. The spine marked E in the fin of 

 Parexus (fig. 51) is a dermal structure not homologous with the 

 cartilages similarly lettered in the accompanying figures; but here 

 Dr. Dean appears to frame an hypothesis that cartilages are clustered 

 in its interior. Finally, we have never observed the pineal foramen 

 in Ctenodus and Paladaphus noticed on p. 55. 



The Lampreys and their allies form the subject of chapter iii 





