REVIEWS 685 



Half the volume is devoted to systematic palaeontology. The sec- 

 tions on the Ostracoda and Bryozoa are the work of Dr. Ulrich and Dr. 

 Bassler. The other phylla have been treated by Dr. Swartz and Dr. 

 Prouty. 



The Cephalopod fauna is strikingly limited in the number of species 

 and genera represented as compared with the richness of this fauna in 

 such states as New York and Illinois. The Crinoidea, which furnish 

 some unusual forms in Maryland, are not included in the scope of the 

 work. The beautifully executed plates leave nothing to be desired in the 

 way of illustrations. 



The information given for each species regarding its horizon varies 

 greatly in preciseness and consequently in value. Concerning the 

 horizon of Drepanellina confluens n. sp., for example, no horizon or 

 formation is given. In contrast with this case of negative information 

 for which the authors are probably in no way responsible, " Mastigobolhina 

 micula, Clinton — one hundred and two feet beneath the top of the Keefer 

 sandstone" may be cited as an example of the precise and model state- 

 ment of the horizon which concludes many of the specific descriptions. 

 Contrasted with this model statement which gives for the fossil not only 

 the formation but the exact location within it, and in addition to this 

 definite information the opinion of the authors that these beds are the 

 equivalent of some part of the New York CHnton, we find a great many 

 cases where the horizon is cited as Clinton. This kind of a horizon 

 citation gives merely the opinion held by the authors at a particular 

 time concerning the correlation of the beds from which a given species 

 is derived in terms of their definition of a time term during a particular 

 year, or term of years, and fails altogether to supply information which 

 would enable anyone to precisely locate it in the Maryland section. 

 Since the attempt was made a few years ago to revise the meaning of the 

 , name Clinton by abandoning the meaning set for it in the later and best 

 work of James Hall, it has lacked the definite meaning which it previously 

 had in the New York Genesee section. The nomenclature used in this 

 volume disregards the conclusions of Chadwick whose detailed strati- 

 graphic work on the Clinton represents the latest work of the New York 

 Survey on this terrane, and fails to accept Bassler's interpretation of the 

 limits of Clinton as given in his Bibliographic Index of Ordovician and 

 Silurian Fossils. The limits set for the Clinton by Ulrich and Stose in 

 1912 also appear to differ from those drawn for it in this volume. The 

 mercurial character which the term has thus acquired in geological litera- 



