ACANTHOCTENUS. 359 
truncate at the apex. Each fang-groove of mandibles with three teeth. Legs spinose; tibia i. and ii. 
with 7-9 pairs of long movable spines beneath ; protarsi i. and ii. with four pairs of long spines beneath. 
Abdomen with small pencils of fine hairs arranged longitudinally down the dorsal and lateral areas. 
Sternum nearly circular. Palpus of female bearing a pectinated claw. Calamistrum consisting of a 
small oval tuft of fine curved hairs on the second fifth of protarsus iv. from the basal end. Cribellum 
consisting of a pair of oval-elongate or triangular concavities divided by a more or less distinct narrow 
septum. 
One genus only of this family is known, exclusively confined to the Neotropical 
region, where there have hitherto been taken but four species—one on the Lower 
Amazons, a second at Pernambuco, the third in Mexico and Guatemala, the fourth 
in various parts of Central America. One or other of the latter species has also been 
recorded from Venezuela and Ecuador. 
ACANTHOCTENUS. 
Acanthoctenus, Keyserling, Verh. zool.-bot. Ges. Wien, xxvi. p. 693 (1876). 
Type A. spinigerus, Keyserling (¢). Mexico. 
The generic characters will be found amongst those of the family. The spiders 
themselves live under the bark of trees or beneath stones, constructing a loose web, ' 
clothed with a flocculent silk. They squat flat against the surface, after the manner 
of the Sparassids, and move with great rapidity when disturbed. 
Two species are known to me as occurring in Central America. ‘They may be 
distinguished as follows :— 
Males. 
a. Tibia of palpus, seen from above, scarcely longer than the patella, curving 
outward and distinctly gibbous at the middle of the outer side. Tibial 
spur stouter, its point blunt and directed at right angles outward. . . . spinigerus, Keys. 
b. Tibia of palpus, seen from above, distinctly longer than the patella, parallel- 
sided, straight, not gibbous on the outer side. Tibial spur more slender, 
more acutely pointed, directed obliquely forward . . . . . . . . « spinipes, Keys. 
Females. 
a. Vulval area narrower anteriorly, but the central pale portion is broader at the 
posterior margin. ©. ee ee eee ee ee .  Spinigerus. 
b. Vulval area broader anteriorly, but the central pale portion narrows towards 
the posterior margm . «1 1 ew ew ww ee ee ee wo Sptnipes. 
Norsz.—I am not at all confident that the two forms of the female vulva here figured belong to distinct 
pecies. Neither, in any case, can I be sure to which of the two males here distinguished these females belong, 
whether they represent one or two species. If they are the sexual complement of spinigerus, Keys., then this 
name has priority and spinipes becomes its synonym, and the male here referred to spinipes requires 
another name. If, however, the females are all the sexual complements of this latter male form then the 
name spinipes will stand and the male spinigerus will be without its sexual complement. 
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