416 Mr. A. G. Butler's List of the 
Koch's diagnosis iims as follows : — " The tarsi of all the 
legs inarticulate ; the tarsal joint short, the terminal joint 
of the palpi hidden." 
M. Dufour characterized the two species Rhax melanus 
and R. phalanc/ista thus : ~" all the tarsi with two joints ;" 
this character, although it does not agree with that given 
by Koch, certainly favours the latter author's view of the 
importance of tarsal characters for the subdivision of the 
GaleodldcB ; M. Dufour also characterized G. hruniiipes 
and G. quadrifjerus thus, — "posterior tarsi with eight 
joints, intermediate tarsi with six joints : " and G. nigri- 
palpis — " posterior tarsi with eight joints, intermediate 
tarsi with five joints:" and he believed that if Koch had 
known of these species, he would not have attempted to 
subdivide the Galeodida as he did. 
It appears to me that in a group so extensive as Gale- 
odes, and comprising species so similar to one another in 
external appearance, it is exceedingly desirable to take 
advantage of any constant structural characters for the 
formation of genera, and so to reduce as much as possible 
tlie labour of determining the species : that this was Koch's 
view also appears evident from the number of genera 
which he formed in his " Arachniden," some of them 
indeed founded upon characters too slight to be of vahie ; 
1 think, therefore, that had he known the species described 
by M. Dufour, and seen them to be distinct in structure 
from Rhax, Aellopvs, Solpnga, Galeodes, and Gluvia, he 
would in aU probability have added one or two genera for 
their reception, and I think he would have been perfectly 
justified in so doing. 
That Rhax is a good genus (whatever maybe the value 
of the others) I have no doubt whatever; not only is the 
group distinct to the eye, but the tarsi (according to 
M. Dufov^r) differ in their articulations, and the mandibles 
are distinguished by an entirely difierent character of 
dentition ; this difference has never before been so well 
illustrated as on M. Dufour's plates, and I consider it a 
highly important one, as being easily seen, even in dried 
specimens. 
In the present paper I shall adopt provisionally the 
whole of Koch's genera, believing, as I do, that they Avill 
eventually be adopted without hesitation, and fully satisfied 
that Rhax, at any rate, will always be considered a good 
and well-marked genus. 
