Reviews — Prof. Br. Nicholson — British Stromatoporoids. 123 



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I. — A Monograph of the British Stromatoporoids. By H. 

 Alleyne Nicholson, M.D., D.Sc., etc., Begius Professor of 

 Natural History in the University of Aberdeen. Part I. General 

 Introduction, pp. iii. and 130, with 11 Plates. (Pakeontographical 

 Society's Volume for 1885.) 



THE nature and systematic position of the widely-disti'ibuted 

 groups of Palaeozoic fossils, known genei-ally as the 

 Stromatoporse, now styled by Prof. Nicholson " Stromatoporoids," 

 have given rise to very varied differences of opinion, ever since 

 the first genus was described by Goldfuss in 1826. The group has 

 been alternately regarded as belonging to Foraminifera, Sponges, 

 Polyzoa, Corals, and finally to Hydrozoa. Such diversities of opinion 

 have not merely been maintained by those earlier authors, whose 

 knowledge of the organism was limited to its form and other external 

 features, but they have been also held by later investigators, who 

 have studied its microscopic characters in thin sections. The 

 opposing views may be to some extent explained by the different 

 appearances presented by the fossils under different conditions of 

 fossilization, by limited investigation, and in no small degree by the 

 influence of previous lines of study on the part of the respective 

 authors. Thus, for instance, Sir J. W. Dawson finds certain 

 structures in Stromatoporoids resembling those in the supposed 

 Foraminifer, Eozoon Canadense, and dismisses almost with con- 

 tempt the view of Mr. H. J. Carter that Stromatoporce are 

 skeletons of hydroids allied to Hydractinia. This latter view is, 

 however, now generally received; whilst Sir J. W. Dawson's opinion 1 

 that " Stromatopora and Eozoon may both be regarded as large, 

 sessile, laminated calcareous Bhizopods," has not been supported by 

 later authors. Prof. Sollas, on the other hand, places Stromatopora 

 among the Vitreo-hexactinellid sponges, an opinion which was 

 subsequently qualified by the statement that Stroma toporce included 

 organisms of very different affinities, some being siliceous sponges, 

 some related to Millepora and Hydractinia, and some with relation- 

 ships yet undetermined. Baron Bosen referred the group to Keratose 

 sponges, in which the fibres had become silicified or calcified in 

 fossilization. Prof. Nicholson also, in a joint memoir with Dr. 

 Murie, reached the conclusion that the Stromatoporce belonged to 

 a peculiar extinct group of Calcisponges. To Mr. H. J. Carter 

 belongs the credit of having first indicated the relationship of the 

 Stromatoporoids to the recent Hydractinia, and their extinct allies, 

 and this view has gradually been adopted by palaeontologists 

 generally. 



The difficulties attending the study of this group of fossils may 

 readily be inferred from the various opinions held with respect to 

 their characters, and the present attempt to overcome the obstacles 

 which have baffled previous observers implies no small amount of 

 courage on the part of the author. The only sure method of investi- 

 1 Quart. Journ. Geol. Soc. vol. xxxv. 1879, p. 50. 



