324 Mr. F. O. P. Cambridge on 
islands of the Greater and Lesser Antilles and the more adja- 
cent regions of the mainland all round. 
If it be asked what are the final tests of a distinct species 
of spider, one can only say that a long course of experimental 
interbreeding under perfectly natural conditions, settling 
which would breed together and which not, might solve the 
problem. Such an investigation being impossible, one has to 
fall back on the comparative anatomy of the genitalia. If 
these are identical in a number of individuals of different sexes, 
the latter are held to belong to one and the same species. If 
not structurally identical, then the forms are regarded as 
distinct species, on the supposition that two different forms of 
male organ are not adapted to the fertilization of one form of 
the female organ. 
Fam. Theraphoside. 
LYROSCELUS, gen. nov. 
Femur iv. not scopulate on inner side. ‘arsal pads not 
divided ; scopula interspersed with a few scattered hairs only 
towards the base. Protarsus i. scopulate to base, with a single 
spine on inner side only at the base. Apex of tibia i. bical- 
carate. Protarsus iv. scopulate at extreme apex only. Legs 
spinulose, especially iii. and iv. Apical third of labium and 
inner anterior angle of coxa of pedipalp spinulose.  ‘T'ro- 
chanter of leg i. with 10-12 stout clavate stridulating- spines 
on the inner side, extending over the upper two thirds of the 
segment; opposed to these are 15-16 long, stout, slightly 
clavate spines, situated on the outer side of the trochanter of 
the pedipalp, extending over the central half of the segment. 
Lyroscelus Bonhotei, sp.n. (Pl. VII. figs. 6, 6 a.) 
Colour. Carapace clothed with a very pale bronze covering 
of shaggy hair. Mandibles brown, with a basal dorsal 
clothing of the same pale bronze hairs. Legs clothed with 
coffee-brown hairs, interspersed on the protarsi and tarsi with 
Jong scattered rufous hairs. Femora and patelle of legs, 
especially i. and il., clothed with golden- bronze hairs over the 
dorsal and externo-lateral areas. 
Abdomen clothed with darker coffee-brown hairs, inter- 
spersed, especially towards the spinners, with long rufous 
1airs. 
Sternum and coxe of legs coffee-brown ; coxe of pedipalp 
and fringe on fang-groove of mandibles bright rufous. 
Measurements. —Carapace 18 x 15 millim. ; pat.+tib. i. and 
