XIII APPENDAGES Ber 
while the chelicerae are pushed forward, no orifice is visible, but 
on careful examination it will be found that what appears to be 
a thick and fleshy labium is, in reality, two organs. The labium 
is thin and flat, and closely opposed to its upper surface is a 
somewhat flattened cone. This is the “rostrum,” and when it 
is separated from the labium the buccal orifice is disclosed. 
In a few spiders (Archeidae) in which the chelicerae are far 
removed from the mouth, the rostrum is tolerably conspicuous, 
but in most it is so hidden as to have escaped the observation of 
the great majority of observers. Schimkewitsch considers it 
homologous with the labrum of insects, but Simon thinks that 
it represents all the insect mouth-parts reduced to an exceed- 
ingly simple form. It is more probable that a beak consisting 
of a simple labrum and labium was a primitive Arachnid char- 
acteristic. If the rostrum be removed and its inner (or posterior) 
surface examined, a lance-shaped chitinous plate, the “ palate,” 
becomes visible. It is furrowed down the middle by a narrow 
groove, which is converted into a tube for the passage of fluids 
when the rostrum is opposed to the labium. 
Pedipalpi—The pedipalpi are extremely leg-like feelers, and 
are six-jointed, the metatarsal joint of the ambulatory legs being 
absent. The joints, there- 
fore, are the coxa, trochanter, 
femur, patella, tibia, and 
tarsus (Fig. 178).' 
In the Theraphosae the 
coxa resembles that of the 
ambulatory leg, but in other 
spiders it is furnished, on 
the inner side, with a blade- 
like projection, the “ maxilla ” 
(Fig. 178). The shape of the 
maxillae and the degree of Fic. 178. —Pedipalp of Tegenuria domestica & . 
their inclination towards the x 5. 1, Coxa; 2, maxilla; 3, trochanter ; 
labium are of considerable z ae a eo Cp Abie Ar She 
taxonomic importance. The 
inner border of the maxilla is furnished with a tuft of hairs, 
1 Pickard-Cambridge (Spiders of Dorset, 1879-1881) omits the coxal joint, which, 
with its lobe, he calls the maxilla, and therefore gives only five joints, which 
he names axillary, humeral, cubital, radial, and digital. 
VOL. IV NG 
