1916.) EF. H. Graveiy : Indo-Australian Thelyphonidae. 61 
In my preliminary note on the evolution and distribution of 
the Thelyphonidae it was suggested that the distinction between 
the genera with and without keels between the median and lateral 
eyes was extremely ancient, and consequently of fundamental 
importance. The discovery of species, clearly allied not to the 
keeled but to the keelless group, in which this ridge, though not 
very strong, is quite distinct, renders this hypothesis less probable 
than it previously appeared. The fact, however, that the species 
of the keelless group which have the tibial apophysis of the male 
least specialized appear, so far as is known, to agree in having 
tibial spurs on the fourth pair of legs only, no matter from what 
part of the world they come, seems to imply that the group 
may really be an old one which once had a more continuously ex- 
‘tensive distribution than it has at present. The only known ex- 
ceptions to this rule are Hypoctonus oatest and one or two other 
species leading up to the most specialized section of the latter 
group—a section confined to the neighbourhood of Burma and 
Assam. Nothing is, however, known of the male of the single 
African keelless species hitherto recorded; nor is anything known 
of the tibial spurs of the American keelless genus Thelyphonellus, 
in which the male appears to have retained its primitive form 
more nearly than has that of any Oriental species yet described. 
The distinction between the keeled and keelless groups may 
therefore be accepted as being in all probability of fundamental 
importance, with the reservation that weak keels may occasionally 
be developed in species whose other characters, especially the 
form of the tibial apophysis of the male, show them to belong to 
the latter and not to the former group. 
The keelless group is at present divided into an Indian genus 
Labochirus, in which a tooth is present on the inner margin of the 
gnathobase of the arm, and a (mainly) Burmese genus Hypoctonus, 
which is ordinarily without this tooth. But in view of the fact 
that the tooth is now known to be present in at least one species 
whose other characters show it to be a member of the latter genus, 
a revised definition seems necessary. 
The number of legs bearing tibial spurs, a character which is 
correlated with the form of the tibial apophysis of the male’, 
supplies an excellent basis for this definition. It is probable, 
however, that as yet the group is very imperfectly known. For it 
inhabits country which has for the most part been very imperfectly 
explored zoologically, and the range of most at least of its species 
seems to be somewhat circumscribed. For the present, therefore, 
it will probably be best to transfer to the genus Labochirus, 
hitherto restricted to Indian species, the African and Burmese 
species in which only the fourth legs bear tibial spurs, although it is 

| The tibial apophysis of the male has much the same form in the simpler 
members of both groups defined according to the presence or absence of tibial 
spurs on the third pair of legs; but in the more specialized specics without these 
spurs the upper ridge of the tip of the apophysis is most strongly developed, 
while in those with these spurs the lower ridge is larger. 
