434 Records of the Indian Museum. [Vor. XI, 
Pulvilli present; hand able to bend till it forms a right 
angle with the tibia, the terminal spines of which are 
directed sideways; prosomatic sterna small, more or 
less tuberculiform ... ¥ a ... Charontinae, p. 435- 
Pulvilli absent ; hand unable to bend at less than an 
obtuse angle to tibia, the terminal spines of which are 
directed forwards in adults above base of hand ; proso- 
matic sterna broadly expanded, lightly concave or 
flat ae se ire ee Phrynichinae, p. 447. 
The American subfamily Tarantulinae differs from the sub- 
family Charontinae chiefly in the absence of a pulvillus. 
The structure of the arm and hand, though differing in detail 
in different species, is remarkably uniform in plan in the young of 
all the species of Tarantulidae whose development is known to me. 
Considerable changes, however, take place during the growth 
of individuals belonging to the larger species. This is especially 
the case with species of the subfamily Phrynichinae, the hand of 
which is so modified in the adult that each is capable of grasping 
prey without the aid of the other (see Gravely, 1915, pl. xxiv, 
fig. 28 of this volume). In this respect the Phrynichinae may be 
regarded as more highly specialized than the Charontinae, and as 
the structure of the arm and hand presents greater difficulties than 
does that of other organs, the Charontinae may conveniently be 
considered before the Phrynichinae. 
In some respects, however, the former are probably more 
highly specialized than the latter. The jointing of the hind tibiae, 
for instance, which is often less marked, when it occurs, in young 
specimens than in old ones, is carried further in the Charontinae 
than in the Phrynichinae. And it is difficult to think that pulvilli 
can ever have been present in creatures with the habits of the 
Phrynichinae, when these are not found in them at the present day. 
For both Phrynichinae and Charontinae habitually live clinging to 
the underside of stones or logs of wood; and the latter, which 
have pulvilli, can cling in this position to polished glass, whereas 
not even the young of the former, which lack them, can do this. 
The fundamental structure of the arms and hands of the 
Tarantulidae may now be described as it is to be seen, more or 
less distinctly, in the young probably of all species, and in the 
adults of many Charontinae,. The modifications to which it is 
subject during the growth of the more highly specialized forms are 
all in the direction of the specialization of particular spines and 
the loss of others. 
The anterior face of the trochanter is bounded above by a 
dorsal row of spines, and below by a ventral cluster; while be- 
tween these is a middle group or longitudinal row. 
The anterior face of the femur is flattened, and is bounded by 
a dorsal and a ventral row of spines. The tibia is similarly flat- 
tened in front and armed above and below, the spines of the distal 
half of the dorsal row always being much the longest. 
The hand is armed with two spines above and one below. 
Occasionally additional spines are also present. . 
