444 Rev. A. Matthews on Dr. C. Flach’s 
can only be regarded as accessory ; length of limb, form of 
outline, and superficial sculpture must always form the 
principal specific factors—colour and size, except when 
uniformly persistent, are of minor importance. 
But, on the 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, I 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- 
pterygide with which Dr. Flach concludes his essay. 
Betore 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. Allibent 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. Aubé, MM. C. Brisout de 
Barneville, Fairmaire, Reiche, Thomson, Hampé, and other 
friends, so that I may fairly consider that I am in a position 
to speak with some amount of accuracy on their respective 
merits ; and with these preliminary remarks I will now turn 
to the unwelcome task of examining the nomenclature of the 
‘Trichopterygide published by Dr. Flach. 
The first genus in this list which requires notice is Ptent- 
dium, divided in the following manner into four subgenera :— 
Prenrpium, Erichson. 
Matthewsium, Flach. 
ovulum, Flach. 
Gressnert, Gillm, 
Ledert, Flach. 
levigatum, Gillm. 
atomaroides, Matth., ex typ. 
Bruckii, Matth. 
turgidum, Thoms. 
Wankowiezium, Flach. 
untermedium, Wank. 
? Wankowiesv, Matth. 
Var. Weisei, Flach. 
Brenskei, Flach. 
Ptenidium. 
Pensiyi, Flach. 
turgidulum, Flach. 
fuscicorne, Erichs. 
picipes, Matth. 
obscurtcorne, Mots. 
