APPENDAGES 



i2I 



while the chelicerae are pushed forward, no orifice is visible, but 

 on careful examination it will l)e found that what appears to be 

 a thick and fleshy lal)iuni 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 witli the labrum of insects, but Simon thinks tliat 

 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 tliat of the 

 ambulatory leg, but in other 

 spiders it is furnished, on 

 the inner side, with a blade- 

 like projection, the " maxilla " 

 (Fig. ITS). The shape of the 

 maxillae and the degree of „ ,_„ r. ,■ , ^^ 



" 1" IG. 1 / 0. — Pedipalp of Tegenaria domestica S . 



their inclination towards the x 5. l, Coxa ; 2, maxilla ; 3, trochanter ; 



labium are of consideralfle J ^T""; ' ^' p^**^^^'^ ' ^' ^^•^'^ - '' ^^^^^"^ • 



8, palpal organ. 



taxonomic importance. The 



inner l)order of tlie maxilla is fvu'nished with a tuft of hairs. 



^ Pickard-Cambvidge {Binders 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 Y 



