988 MR. F. A. POTTS ON 
Minor variations are found, according to whether the sides of 
the head are curved or straight, to the degree of attenuation and 
curvature of the tip. 
In none of the species which have been described hitherto 
has a full examination of the notopodial sete been made. Such 
figures and notes as are given are of little value, then, in fixing 
the species; but they show, I think, that the same variations 
which oceur in P. prolifica and anglica occur in all. I have been 
able to compare these with the actual specimens of P. clapareden, 
pictus, and elioti described by Crossland, and this examination 
supports my conclusion that the notopodial sete are too variable 
to base specific characters upon. 
Text-figure 11. 
Sek 
We 
A B ce 
Phyllo chetopterus prolifica. Enlarged sete from 4th segeint. 
The specially modified sete in the fourth segment are always 
figured in descriptions of species, and their configuration is 
sometimes considered to be of diagnostic value. There is, without 
doubt, a recognisable type for each genus of the Chetopterids, 
but the modifications of this are so many, varying even in the 
same individual, that I find it impossible to regard the shape 
of the seta as in any way a specific feature. In all species of 
Phyllocheetopterus, the seta appears to end in a blunt elliptical 
crown. One or both of the sides of this are raised into a cuspate 
ridge, one ridge being generally higher than the other. The 
number of cusps is highly variable, and so is their development. 
Thus in P. prolifica (text-fig. 11, A, B) there are on the highest 
side 3, 4, or 5 cusps, and generally the cusps have a fairly equal 
development. In some cases, however, like text-fig. 11, C, one or 
