REVIEWS 293 



tion of any one species the case stands perhaps a Httle better. But even 

 so, the migration of species is governed by so many factors extrinsic as well 

 as intrinsic that inferences drawn from the fact of abundance can hardly 

 lead to any trustworthy conclusions. 



In short, it seems to me that the authors attach too much and possibly 

 not altogether the correct significance to the fact of abundance. At all 

 events, the matter is not so lightly to be disposed of. 



Regarding their identification, the authors say that they have used 

 conservatism: "Usually, where there is a question concerning the advisa- 

 bility of splitting up an older idea of a species, the old idea is followed here." 

 As the paper is not accompanied by descriptions or figures, it is impossible 

 for the reader to ascertain what breadth of specific limitation is assumed in 

 any case. Fx)r my own part, it has always seemed to me that the relations 

 between faunas are best shown when the discrimination of species is made 

 with the keenest criticism, tempered with good judgment. It is to be hoped 

 that in their final account of the fauna which the authors lead us to expect 

 a refined discrimination of species will be employed. 



The authors note some departures from the taxonomic nomenclature 

 employed in previous papers which the present one in a way seems to 

 summarize and be the fruit of, but the changes are hardly enough to bring 

 the paper abreast of the time in this particular. These changes are, how- 

 ever, purely nomenclatural and do not necessarily affect the accuracy of 

 the conclusions arrived at. They can the more be pardoned because the 

 volume has been a long time in press and doubtless some of them came to 

 the authors' attention after the report had left their hands. 



The paper abounds in typographical errors, chiefly in connection with 

 scientific names, and in other errors for which the printer cannot be blamed. 

 One of the most serious, at least in the estimation of a paleontologist, is 

 that the imprint is for the year 1908, while, as is apparent, the work really 

 did not appear until late in 1909.^ This, of course, cannot be laid at the 

 door of Messrs. Beede and Rogers, nor perhaps the fact that the descrip- 

 tion of the chart begins on p. 359, while the chart is inserted thirty pages 

 earlier, although in the description it is said to follow, thus really confusing 



I In his review of my report on the Guadalupian fauna (Jour. GeoL, XVII [1909], 

 672), Dr. Beede justly criticizes that book for the same fault. I take this occasion to 

 put the facts on record. The pages were approved with the imprint 1908 on Novem- 

 ber 14 of that year. Under ordinary conditions this would have given ample time 

 for publication before the end of the year, but owing to occurrences which could not 

 be foreseen publication was delayed. The copies were received on January 29, 1909, 

 and were immediately distributed so that the actual date of publication should 

 probably be regarded as early in February. 



