Reviews—Dr. R. S. Bassler—Bibliographie Index. 325 
temperature of the asthenosphere is high and the rocks approach very 
closely the liquid condition. 
It is not generally recognized that the conditions of stress necessary 
to set up flow in a plastic substance are very different from those 
required to cause flow in a liquid. 
RAV Tews. 
T.—Ray S. Basster. Breriograruic InpEX oF AMERICAN ORDOVICIAN 
anp Siturian Fossizs. Bull. U.S. National Mus., No. 92. 
2 vols. Washington, 1915. 
IYVHE term ‘‘ American”’ rightly includes the whole of North and 
South America. Under ‘ Ordovician”’ and ‘‘Silurian”’ are 
included all formations that lie between undoubted Cambrian and 
undoubted Devonian. ‘he ‘‘ Fossils” comprise Vertebrates, Inverte- 
brates, Plants, and ‘Tracks of doubtful origin. The words 
‘‘ Bibliographic Index ”’ refer to the bulk of the book, also described 
as a ‘‘Bibliographic List of Genera and Species”. What a 
‘bibliographic list: or index”? would really be is somewhat doubtful : 
what Dr. Bassler has given us isa list of generic names in alphabetical 
order, with a list of the specific names in alphabetical order under the 
genera to which they belong. Under each generic name is given the 
name of the genotype, but it is not stated how this has been 
determined. Dr. Bassler has not ventured to fix one for Orthoceras. 
The generic and specific names are followed by the main references to 
literature. Then, for the species, come the horizon and localities 
(some extra-American), but the type-locality is not distinguished. 
Lastly, the register numbers are given of any type-material of the 
species in the U.S. National Museum. 
The references to literature are brought down to the close of 1914, 
_ except that Schuchert’s ‘‘ Revision of Paleozoic Stelleroidea ” (1915) 
and Springer’s ‘‘Monograph of Crinoidea Flexibilia’”’ (not yet 
published) are also indexed. One does not like to quarrel with 
a good thing; but is there not too much citation of obvious text-books, 
and indeed of other Indexes, such as S. A. Miller’s well-known work ? 
This would be all very well if it did not seem occasionally to lead to 
the exclusion of far more important references. The long list under 
Caryocrinites, for instance, contains no reference to the classical memoir 
of L. v. Buch, except by way of the species C. ornatus ; nor does the 
discussion of this genus and of the allied Strabalocystites in 
Paleontologia Indica (1906) find mention even under one of the 
various species. There is a method in this apparently, for under 
Petalocrinus, instead of quoting Bather’s elaborate study of the genus 
published by the Geological Society, Dr. Bassler refers only to the 
abstract report, and even then, not to the Proceedings of the Society, 
but to the Grotocrcat Macazine; it is only when his new species are 
indexed that Bather’s paper is referred to. To parody Polonius, 
‘‘Though this be method, yet there’s madness in it.” The 
Gxotocicat Macazine. here unduly favoured, is on more important 
occasions ignored: Lebetodiscus (Grot. Mac., 1908, p. 550) and 
