326 Mr. F. O. P. Cambridge on 
much less evident and almost or entirely absent on the 
femora. 
Several of these forms have been described as different 
species by various authors, the differences being based on the 
presence or absence of the horns on the carapace and the 
nature of the tufts on the legs. 
I am, however, myself not able to confirm the distinction of 
species on these characters, and strongly suspect that in reality 
there is only one species embracing all these forms. It is 
therefore very important that we should be able to examine 
males and females of these large and easily recognizable 
spiders from as many of the islands of the Greater and Lesser 
Antilles as possible, and especially from Jamaica, for it was 
in this island that the type of Ar. clavipes of Linneus was 
taken. 
At first sight it might be supposed that there were either 
two species, one with and the other without the cephalic 
horns, and two varieties of each of these, one with the legs 
thickly tufted and the other with the legs much less densely 
clothed with hairs; or that there were jour species, two of 
each group of horned and notehorned forms, based on the 
differences in the leg-tufts. 
There is another possibility that the horns are not of 
specific importance, while the tufts on the legs are. This 
would give us two species, the presence or absence of horns 
being ignored. 
One is, however, strongly urged to the conclusion that 
neither of these characters 1s of specific importance, because 
after comparing many examples of the forms known as 
clavipes, Linn., and cornuta, Pallas, of both sexes, it is seen 
that the males of both these forms are inseparable; the palpal 
organs are identical in form. ‘That is to say, that the males of 
the pure clavipes, whose females are without tubercles on tiie 
carapace and have dense tufts on the femora and tibiew of i. 
and ii. and on tibia iv., cannot be distinguished from the 
males of the pure cornuta, whose females have two distinct 
tubercles on the carapace and scarcely any fringing hairs on 
legs i, ii, and iv. However, there is not sufficient material 
to be absolutely sure that this is the case, though of the 
former there are adult males and females in Mr. Bonhote’s 
collection, and also others in the British Museum; while of 
the latter I have myself taken many examples on the Lower 
Amazons, and one pair actually in copulation. 
Of the females, then, there are four distinct forms :— 
