Geology and Natural History. 415 



15. Devonian Fishes of Iowa; by Charles R. Eastman. 

 Annual Report, Iowa Geological Survey, Vol. XVIII, pp. 29-386, 

 pis. i-xvi and 41 text figures. 1907. — This is a very exhaustive 

 work on the Devonian Fishes, not only of Iowa but also of the 

 North American Devonian, while the fishes of Great Britain and 

 Europe are of necessity treated for comparison. Chapter I is of 

 an introductory character, in which the author discusses the aim 

 and general outlook of paleontological inquiry, and the relations 

 of paleichthyology to biology. Chapter II is geological and in 

 it is considered the stratigraphy of the Devonian fish-bearing 

 beds of Iowa, which form a belt averaging fifty miles in width, 

 stretching along the Cedar river from the Minnesota line to Mus- 

 catine County and thence eastward into Illinois. 



The Devonian fauna of the state is peculiar in its undiversified 

 character, consisting almost exclusively of Chimgeroids, Arthro- 

 dires and Lung fishes ; there being a notable dearth of Selachians 

 and but one certainly recognized genus of Crossopterygians. 

 The fish-bearing stages are confined to the Middle and Upper 

 Devonian, their greatest abundance being during the latter period. 



In his discussion in Chapter III of the evolutionary history of 

 fishes, Dr. Eastman denies the possibility of the derivation of fishes 

 from the Arthropod phylum, but finds no theoretical objection 

 to looking upon some of the worm-like Enteropneusta as the pos- 

 sible ancestors of the vertebrate stem. Documentary evidence 

 of this will probably never be obtained, from the impossibility of 

 the preservation of such soft-bodied creatures in the rocks. A 

 further discussion of the main evolutionary changes of the fishes 

 follows, showing remarkably sudden fundamental advances ; the 

 " expression points " of Cope : such as the acquisition (1) of paddle- 

 like paired fins ; (2) shortened fin-bases but persistent heterocer- 

 cal tail ; (3) complete balancing fins and homocercal tail and (4) a 

 complete internal skeleton. 



The discussion of the general classificatory scheme includes a 

 tabular view of the classification to suborders. 



Chapter IV discusses the systematic account of Devonian fishes, 

 with special reference to those of Iowa and the adjoining states. 

 Herein are carefully described and compared many species included 

 in 32 well-known genera, and several more, the family position 

 of which is doubtful. Chapter , V embraces three admirable 

 faunal lists ; one of the Lower Devonian localities in New Bruns- 

 wick, Nova Scotia, Quebec and Aroostook Co., Maine ; and the 

 Middle and Upper Devonian, both of which are included in 

 Iowa. The excellent plates are from wash drawings and 

 photographs and include three of Professor Schuchert's paleo- 

 geographical maps ; that of Middle Devonian at the close of the 

 Onondaga, at the close of the Hamilton, and during Upper 

 Devonian time. 



The work is a masterful one, written in Dr. Eastman's delight- 

 fully readable style, and will prove a great boon, not alone to the 

 systematic paleichthyologist, but to the general student of paleon- 

 tology and evolution as well. e. s. l. 



