372 Mr. F. O. Pickard-Cambridge on 
keys are set in the lower margin of the basal joint of the man- 
dible, while the keys themselves are on the inner face of the 
coxal joint of the palpus. In Phormingochilus, on the other 
hand. this position is reversed, the keys or rods being on the 
mandible, while the opposing spines are on the palpus. These 
beautiful structures, as represented in the two genera men- 
tioned above, have been described and figured in a most 
interesting paper published in ‘ Natural Science,’ vol. vi. 
p. 35, Jan. 1895, entitled “‘ Musical Boxes in Spiders.” 
Amongst other spiders which exhibit an organ of some- 
what similar character in the male sex and in a rudimentary 
form in the female sex, in connexion with the mandibles and 
palpi, we may mention the genus Leptyphantes of the family 
Theridiide and some other genera commonly included under 
the name Zmeticus. The organ in this case consists of a 
series of transverse grooves, opposed by a small spine set in 
the apex of a minute conical prominence, situated near the 
base on the inner side of the femoral joint of the palpus, 
which works upon and across the grooves. 
These organs were described and figured long ago by 
Mr. F. Maule-Campbell, of Hoddesdon. 
The sound which these minute organs would emit, if 
indeed any, would of course be far too insignificant to be 
heard by the human ear. 
More interesting on the whole, perhaps, than these is a 
somewhat similar organ discovered on the mandible of the 
genus Thomisoides, consisting, in this case also, of an 
extended series of very highly specialized transverse ridges 
upon the outer surface, while on the opposing surface of the 
femur of the palpus appear from four to six (the number 
varying in different species) small separate tubercles. This 
structure has been described and figured by M. Simon in 
‘Histoire Naturelle des Araignées,’ pp. 268 and 269, and 
also by Mr. Pocock in the paper mentioned above, and is 
found in both sexes of Thomisoides. 
During the past year I have discovered in all the specimens 
of the genus Scytodes, and in both sexes which have come to 
hand from various parts of the world, a structure very 
similar to those in Leptyphantes, consisting of a series of 
short transverse ridges, more pronounced and more widely 
separate towards the apex, becoming finer and more closely 
adjacent towards the base (fig. I., a). On the femoral joint of 
the palpus near the inner basal angle there is a stout conical 
prominence, its apex terminating in a short blunt spine 
(fig. IL., a). This would, when the palpi were moved to and 
