326 Mr. F. O. P. Cambridge on 



nuicli 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 tliese 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 tiie 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 Linnseus 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 four species^ two of 

 each group of horned and not-horned forms, based on the 

 differences in the leg-tufts. 



There is another possibility tiiat 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 is 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 oi 

 the pure clavipes, whose females are without tubercles on the 

 carapace and have dense tufts on the femora and tibias 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.j and iv. However, there is not sufficient material 

 to be absolutely sure that this is the ease, thougJi 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 : — 



