164 ©. R. Osten Sacken: 
sions, although large, will be slow in coming. Do not introduce new 
genera for every slight deviation from a well-know type, because you 
would soon have no end of new genera, and a growing difficulty in 
discriminating between them. But do not hesitate to establish a new 
genus for a form which cannot be forced into any of the existing 
genera, and which shows distinetive characters in more than one 
organ of its body. Such forms are not very common. I had to give 
up several of the subdivisions too hastily adopted by me in 1868; 
but since that year, having grown in experience, I found necessary 
to establish only four new genera of Tipulidae brevipalpi (only 
one in the present paper). 
An explanation is necessary about some terms I have used in 
stating the synonymy of the genera. I distinguish the exact sy- 
nonym, covering the same group of species, and being another 
name for the same thing, from the ex parte synonym, covering a 
number of species, either larger or smaller, than the generic group 
of species under which the synonym is quoted. This disparity may 
be due to various causes; the synonym may represent a larger genus 
from which the other has been separated (as when Limnobia is 
quoted as a synonym of Dieranomyia); or it may be a subdivision, 
proposed, but, for the present, not adopted (as when Ormosia is 
quoted as a synonym of Rhypholophus); or it may be an ill-con- 
ceived genus, based upon what Erichson called an illusory cha- 
racter (scheinbarer Character), that is a character, which does not 
afford a basis for a natural subdivision, but, on the contrary, sepa- 
rates naturally allied species, and brings together distant ones (like 
the genus Trieyphona Zett., based upon the very secondary cha- 
racter of an open discal cell, which unnaturally separates it from 
the genus Amalopis, formed later, but upon a better basis). A third 
kind of synonymy is formed by what I call the spurious genera, 
generic groups based upon the misapprehension of a fact; for in- 
stance, when a genus is formed for one sex only (like the Acantho- 
merid Megalemyia Bigot); or for the sexes of two different genera 
(like Limnobiorhynchus), or when it is based on some character 
which has no existence in reality (like the genus Synapha Meig., 
based on an accidental abnormity of the venation in a specimen; 
or the Bombylid genus Zeterostylum Macq. that owes its existence 
to some dust on the antennae of the type specimen, which Macquart 
mistook for a pubescence; or the genus Oeroctena Rond. which, to 
all appearances, is based upon a specimen to which the head of 
another species had been glued). Spurious genera should be entirely 
eliminated and have no claim to priority. 
