444 Rev. A. Matthews on Dr. C. Fluclis 



can only be regarded as accessory ; lcn;_''th of limb, form of 

 outline, and superficial sculjtture must always form the 

 ]n-incipal specific factors — colour and size, except when 

 uniformly persistent, are of minor importance. 



Ikit, on tiie other hand, anatomical characters, especially 

 the organs of the mouth and the comparative shape and 

 disposition of the various parts of the external skeleton, must 

 be regarded as the only true generic distinctions. 



Such, 1 believe, are the rules by which generic or specific 

 separations should be regulated. But all these rules seem to 

 have been disregarded in the nomenclature of the Tricho- 

 pterygida3 with which Dr. Flach concludes his essay. 



Before entering into a detailed examination of this nomen- 

 clature I must premise that in my own collection there are 

 authentic types from the collections of M. AUibent and Col. 

 Motschulsky of the greater number of the species described 

 by those authors, together with types of their own species 

 kindly presented to me by Dr. Aubd, MM. C. Brisout de 

 Barneville, Fairmaire, Reiche, Thomson, Harape, and other 

 friends, so that I may fairly consider that I am in a position 

 to speak with some auiount of accuracy on their respective 

 merits ; and with these preliminary remaiks 1 will now turn 

 to the unwelcome task of examining the nomenclature of the 

 Tricl)opterygida3 published by Dr. Flach. 



The first genus in this list which requires notice is Pleni- 

 diuviy divided in the following manner into four subgenera : — 



PxENiDiUM, Ericbson. 



Matthewsium, Flacli. 



ovulum, Flacli. 

 Gressneri, Gillm. 

 Lcderi, Flach. 

 Icevif/atum, Gillm. 



afomaroiden, Matth., ox lyp. 



Bntckii, Mattb. 

 turyidum, Thorns. 



li'ankuwieziuvif Flach. 



intermedium, Wank. 



? Wanhoiciezii, Matth. 

 Var. Ifcisei, Flach. 

 Brenskei, Flacli. 



P/ciiidiuni. 



Pensiyi, Flach. 

 turyiduhim, Flach. 

 fuscivoniv, Erichs. 



pii'lpcx^ Matth. 



ohfcu'ivonir, Mots. 



