Synonymic List of the European Trichopterygide. 443 
to reconstruct, the nomenclature of the whole family, and my 
purpose in the present paper is to consider the alterations 
proposed by Dr. Flach and to set plainly before entomolo- 
gists my own views, where they differ from those of Dr. Flach, 
and, having done this, to leave it in their hands to form an 
unprejudiced opinion on the comparative merits of the systems 
in question. 
The changes of nomenclature proposed by Dr. Flach form 
a leading feature in his essay and require special notice. The 
manner in which he has treated the genus Péti/éum exhibits a 
characteristic example of his style. He has, in fact, adopted 
an arrangement suggested long ago by Col. Motschulsky, 
dividing this very complex genus into many subgenera. 
The creation of what are termed subgenera has always 
appeared to me objectionable for many reasons: it is impos- 
sible to define a subgenus with accuracy sufficient to enable 
a student to determine the proper position of any doubtful 
species ; if this could be done, and the subgenus proved to 
exhibit unmistakable anatomical characters, it would become 
a true genus, and must be designated as such in any subse- 
quent work, Col. Motschulsky’s separation of Ptinella from 
Puilium is a clear proof of the truth of what I have said, for 
no one since his time has ever thought of reuniting those two 
genera. Ifit had been possible I would willingly have retained 
Micrella, Oligella, and other genera which he proposed at 
the same time as Ptinella; but I could find in these no true 
persistent generic characters; the differences which they 
exhibit are merely specific, e.g. the short transversely-jointed 
antenne of P. Kunzet merge gradually through other species 
whose thorax is equally devoid of channels into the long 
slender-jointed antenne of P. exaratum, and the same may 
be said of their superficial sculpture and other differences. I 
found therefore that generic separation could not be sup- 
ported by anatomical evidence, and was content to retain in 
the old genus the greater part of its former species, distin- 
guishing its various divisions by sculptural characters alone 
—thus avoiding the confusion of a multiplicity of indefinite 
generic terms. But even if subgeneric names should be 
deemed advisable, I consider it unjust as well as uncourteous 
to appropriate to your own credit names previously published 
by another author, although they be but imperfectly charac- 
terized. Be this as it may (for genera are at the best mere 
arbitrary divisions, depending on the peculiar ideas of indi- 
vidual authors), in dealing with species greater caution is 
required. ‘The characters which distinguish species are 
mainly superficial: anatomical variation, though often useful, 
