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Annals of the Transvaal Museum 
value, and that, so long ago as 1870, Mr O. P. Cambridge made the same j 
suggestion, but in both instances the accompanying propositions are so 
obviously untenable that one may reasonably hesitate to accept their view on j 
this point: and indeed, Mr Tucker himself rejects the simultaneous proposal 
of M. Simon to restrict the use of the generic name Idiops to the tropical 
American species. Idiops and Acanthodon were not founded on specimens 
of the same sex ; there seems to be no evidence that they came from the same 
part of Brazil — a rather large country — and though apparently only two 
Idiopine genera are recorded from that part of the world it is very probable 
that more do occur. Petrunkevitch in his recent Index Catalogue of American 
Spiders remarks thus : “ especially the tropical countries of Central and South 
America will yield for a long time to come an inexhaustible amount of new 
forms.” Less than a generation ago, only one Idiopine genus was recorded 
from S. Africa: since then, half-a-dozen genera have been recognized, all 
founded on characters of female specimens. It is important to note that 
amongst Idiopine spiders the females afford better generic characters than 
males, and that males of related genera, being more generalized than females 
(except as regards purely sexual characters), are very easily confused together, 
in spite of the fact that in specific differentiation the males provide more 
tangible characters : to illustrate this, I need only mention that males of Galeo- 
soma are almost completely devoid of the one character which so markedly 
distinguishes the genus, and thus are very like males of Acanthodon. It 
seems to me therefore that the identity of Idiops with Acanthodon should be 
regarded as sub judice. 
Again, I have previously explained in what sense I employed these terms 
Idiops and Acanthodon (. Annals Durban Mus. 1. p. 225): in thus limiting the 
generic groups, I have merely followed Dr Purcell (Trans. S. Afr. Phil. Soc. \ 
xv. p. 1 1 8), but on ascertaining that S. African females referable to the genus 
Ctenolophus are generically identical with the type of Acanthodon, I have 
not hesitated to abandon the name Ctenolophus in favour of Acanthodon. 
Assuming the correctness of Mr Tucker's statement in the following extract 
from his account, it would seem that Idiops and Acanthodon may each be 
maintained in their original sense with propriety: “It may be mentioned 
that Ctenolophus and Idiops differ in one respect, namely, the latter has two 
rows of teeth on the cheliceral groove whilst the outer row is represented in 
Ctenolophus by minute denticles only : this by itself is perhaps hardly sufficient 
for separation, though fairly constant, but would no doubt serve to divide the 
group into two main classes.” 
On this, I may remark that all we require of a character for generic purposes 
is constancy : a small character is more important than a large one, if it is more 
constant. 
As a matter of fact, this dentition character presents intermediates 
between the Ctenolophus type and that to which the term Idiops was re- 
stricted by Dr Purcell. When but few species were known, it was easy enough 
to limit such groups as Ctenolophus, Idiops, and Gorgyrella, but the more 
we increase our knowledge of the fauna, the more we realise the impossibility 
of drawing sharp lines between the genera. However, as a matter of conveni- 
ence it seems better to retain the names Acanthodon and Idiops for alternative 
names), either as genera or as subgenera: for the two groups have some 
geographical significance. Various species of Acanthodon are known from 
the Cape Province, but not a single Idiops: on the other hand, the Indian 
species seem to be true Idiops (cp. I. biharicus Gravely). 
