102 REV. O. P. CAMBRIDGE ON THE GENUS IDI0Ps. [Feb. 10, 
Mygalides. Subsequently M. Guérin-Méneville (without any re- 
ference at all to the genus established by M. Perty) founded the 
genus Acanthodon upon another Spider, undoubtedly congeneric with 
that upon which the genus Idiops had been previously established 
(see ‘ Arachnides du Voyage de la Favorite,’ and ‘ Revue Zoologique,’ 
1838, p. 10). This genus, Acanthodon, was afterwards, in the 
Supplement to his history ‘Des Arandides,’ included in ‘Ins. Apt.’ 
tom. ii. p. 234, by Baron Walckenaer, who also seems to have over- 
looked its identity with Idiops. Since that time nothing appears to 
have been published upon it. The present occasion, therefore, seems 
a fit one for the re-establishment of M. Perty’s genus, and the recti- 
fication of the erroneous reference to his species by Walckenaer in 
the work above quoted (Ins. Apt. tom. i. p. 379, where the specific 
name of Perty’s Spider is also erroneously given as Idiops aculeatus, 
whereas the name given it in Del. An. Art. Bras. is Idiops fuscus). 
Of the species* which are now included in the genus Idiops, 
three (Idiops fuscus (Perty), I. kochit, n. sp., I. petitii (Guérin)), 
are from two widely separated localities in South America (Brazil 
and the Amazons); the fourth (I. sigillatus, nu. sp.) is from the 
Swan River, West Australia, and in many respects a most remark- 
able species ; the fifth is from Beiriit in Syria. 
Fam. MYGA.IpDEs. 
Gen. Ip1ors. 
Idiops, Perty, Del. Anim. Artic. Bras. p. 197, 1830-34. 
Acanthodon, Guérin, Arachnides du Voyage de la Favorite, cl. 
viii. pl. 16. figs. 1-8 ; Revue Zool. 1838, p. 10; Walck. Ins. Apt. 
tom. li. p. 234. 
Characters of the Genus.—Cephalothorax large, oval, in some 
species uniformly convex above ; in others the caput is more or less 
elevated, and the sides as well as the thoracic portion depressed. 
Eyes unequal in size and disposed in three transverse rows, 2, 2, 
and 4; this last row, the hindmost, is much the longest, curved, 
and not far behind the second, or intermediate row; while the fore- 
most one is placed at a considerable distance in front, and only just 
above the insertion of the falees; they may also be described (see 
Guérin, l. e. sup.) as disposed in two groups,—the first placed on the 
anterior margin of the cephalothorax, and composed of two eyes near 
to each other ; the second considerably behind and forming a longish 
narrow transverse oval figure, composed of six eyes. 
Falces strong, promiment, and generally armed at their extremi- 
ties on the upperside with a group of short strong spines. 
Mazille cylindrical, divergent, almost entirely destitute of any 
prominence on their inner extremities, so that (like many others of 
the Magalides) the palpus appears to spring from the very extremity 
of the maxilla. 
* Vide supplementary notice, in which other new species are described, 
posted, p. 152. 
