1896. ] SPIDERS FROM THE LOWER AMAZONS, ea 
of the lateral posteriors and 13 a transverse diameter of the 
former from them. Taking another character—the spinulation 
of tibia i.: in some of these examples there are no spines, in 
some 1, in others 2 or 3; while in one case, tibia i. left side had 
2 spines, tibia i. right side had none. The central anterior eyes 
are sometimes 2, sometimes 3 diameters apart; while the lateral 
anteriors vary greatly in their distance from the margin of the 
clypeus, in the immature being quite close *. 
Given, however, plenty of examples of each form, I have no 
doubt but that certain characters might be tabulated which would 
be broadly true of the various forms, but only then to be used with 
caution. 
Of the three forms—A. hartii, A. crassipes, and A. wallacei—of 
which I have been able to compare the actual types, the form of the 
cephalic area furnishes a good differential character, while the spinu- 
lation of tibia i. furnishes another, and the form of the sternum a 
third. But of these species I have seen only five examples (females) 
of A. hartit and one (female) of A. crassipes. I venture to think 
that no satisfactory conclusions will be arrived at until arachno- 
logists are willing to hand over all available material of a particular 
genus to some one or other who is prepared to take the trouble to 
thoroughly compare every specimen and tabulate the characters. 
At present there is confusion of tongues and hair-splitting dispu- 
tation concerning the fraction of a difference in the distance 
between particular eyes, whereas the examination of a long series 
usually proves that these same disputed distances are themselves 
constantly variable quantities in the same form. 
The table given below will probably need considerable modifica- 
tion when a long series of forms is subjected to examination. 
A. Tibia i. with a series of 5-13 spines on inner side. 
1, Anterior row of eyes a little wider than posterior.. 4. caraiba, Sim. 
2. Anterior row of eyes not wider than posterior. 
a. Tibia i. with 5-6 spines on inner side ; tibia ii. 
without spines on inner side ................06065 A. scalops, Sim. 
6. Tibia 1. with 9-15 spines on inner side; tibia ii. 
with 1-3 spines on inner side ..............2...666 A, hartii, Poe. 
B. Tibia i. without any spines, or with 1-3 only on inner 
side. 
I. Central posteriors smaller than laterals. 
1. Central posteriors scarcely smaller than laterals, 
a. Tibia i. with three small spines on inner side. A. crasszpes, Keys. 
6, Tibia i. without any spines on inner side ...... A, rojasi, Sim. 
2. Central posteriors much smaller than laterals... 4. valencianus, Sim. 
II, Central posteriors reniform, Jarger than laterals. A. wallacei, mihi. 
The characters of A. hartit and A. crassipes have been taken from 
the types; the characters of the other species are taken from 
M. Simon’s descriptions (Ann. Soc. Ent. Fr. 1889, pp. 176-177). 
They must, however, be used with caution. 
1 Mr. Pocock has observed similar differences in the characters at different 
stages of A. hartii, Ann. Mag. Nat. Hist. ser. 6, xvi. p. 195. We 
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