28 



THE ENTOMOLOGIST. 



of Velia, has priority as a genus over Hydroessa, Burmeister (full 

 genus 1835).* 



Ex. 2. Corixa, Geoffr., 1762, has type geoffroyi, Leach. The 

 typical subgenus is therefore the section containing geoffroyi, 

 Leach (i. e. Macrocorisa, Thomson, which ought to be known as 

 Corixa, Geoffr., in sp.), and not that containing sinaio. (Linn.), 

 which is not the type of the genus. I have previously rectified 

 the synonymy of the subgenera of Corixa in the Entom., 1898, 

 p. 252.t 



y If a genus, having no type assigned, be divided into two 

 or more subgenera (none of the latter bearing the generic name), 

 the fixation of the genotype (and of the typical subgenus) may 

 be determined subsequently as follows : — 



(a) Any subsequent author has the right to fix the type of 

 the genus out of any one of the subgenera, the name of that 

 subgenus then becoming a true synonym of the genus. If all 

 the subgenera be raised to full rank at the same time, the above 

 procedure takes place. N.B. If a genus, having no type assigned, 

 be divided into two or more subgenera, one of which bears the 

 generic name, the type must subsequently be fixed from that sub- 

 genus. 



(S) If some of the subgenera be raised to generic rank, the 

 remaining one falls as a synonym of the genus if one be left, or 

 a comes into operation if two or more be left. 



All these unavoidably complicated methods of type-fixation 

 would have been obviated, had authors always unmistakably 

 indicated (since 1794) the types of their new genera ; unfor- 

 tunately, many modern authors still continue this neglect. 



(^.) Many genera which were undoubtedly strictly co-extensive, 



each with some other genus or genera, originally , have been, 



through the operations of later authors, made heterotypical and 

 used separately, e.g. (1) Asiraca, Latr., 1796, and Delphax, 

 Fabr., 1798; (2) Poekilloptera, Latr., 1796, and Flata, Fabr., 

 1798 ; (3) Laternaria, Linn., 1764, and Fulgora, Linn., 1767 ; 

 (4) Ploiaria, Scop., 1786, and Emesa, Fabr., 1803 ; (5) Neides, 

 Latr., 1802, and Berytus, Fabr., 1803 ; and many others. 



* This is in direct opposition to the opinion given in my " Guide to the 

 Study of British Waterbugs " (Entom. 1898-1900), when treating of the genus, 

 f I was wrong, however, in proposing " Basileocorixa" for the " striata " 

 group ; amend as follows : — 



Subgenus 3. Arctocorisa, Wallengr., 1894, type carinata (Sahib.), Kirk, 

 1900. 

 = Corixa (Corisa) [coextensive, but heterotypical] auctt., nee Geoffr. 



in sp. 

 = Glaenocorisa (p) and Corisa, Puton, 1880. 

 = Glaenocorisa and Corixa, Saund., 1892. 

 = Basileocorixa, Kirk., 1898. 



(To be continued.) 



