24 INTRODUCTION. 
Genitives in di, a single one being more correct. (See Messrs. 
Allen and Greenough’s ‘‘ Latin Grammar,” Part 1, § 10, 4, b.) 
Nors.— Many still existing scientific names are unworthy 
of retention, but they have not been altered in this volume on 
account of the established rule of priority, which necessitates, 
however, many incongruities. ‘The authorities for these names 
are given in the second index. Great care has been bestowed 
upon the orthography of English names, since great latitude 
exists in this respect, no system being yet established. Certain 
rules have here been followed, with the exceptions produced by 
general or the best usage, 
