OF PERIPATUS CAPENSIS. 879 



ridge, which ends rather abruptly behind, becoming continuous 

 with the dorsal wall of the pharynx. Its projecting edge is 

 armed by a series of small teeth, which are thickenings of the 

 chitinous covering, prolonged from the surface of the body over 

 the buccal cavity. Where the ridge becomes flatter behind, the 

 row of teeth divides into two, with a shallow groove between 

 them (PI. 48, fig. 7). 



The surface of the tongue is covered by the oral epithelium, 

 in parts of which are organs of special sense, similar to those in 

 the skin; but its interior is wholly formed of powerful muscles. 

 The muscles form two groups, intermingled amongst each other. 

 There are a series of fibres inserted in the free edge of the 

 tongue, which diverge, more or less obliquely, towards the skin 

 at the front of the head anteriorly, and towards the pharynx 

 behind. The latter set of fibres are directly continuous with 

 the radial fibres of the pharynx. The muscular fibres just 

 described are clearly adapted to give a sawing motion to the 

 tongue, whose movements may thus, to a certain extent, be com- 

 pared to those of the odontophor of a mollusc. 



In addition to the above set of muscles, there are also trans- 

 verse muscles, forming laminae between the fibres just described. 

 They pass from side to side across the tongue, and their action 

 is clearly to narrow it, and so cause it to project outwards from 

 the buccal cavity. 



On each side of the tongue are placed the jaws, which are, 

 no doubt, a pair of appendages, modified in the characteristic 

 arthropodan manner, to subserve mastication. Their structure 

 has never been satisfactorily described, and is very complicated. 

 They are essentially short papillae, moved by an elaborate 

 and powerful system of muscles, and armed at their free ex- 

 tremities by a pair of cutting blades or claws. The latter struc- 

 tures are, in all essential points, similar to the claws borne by 

 the feet, and, like these, are formed as thickenings of the cuticle. 

 They have therefore essentially the characters of the claws and 

 jaws of the Arthropoda, and are wholly dissimilar to the setae of 

 Chaetopoda. The claws are sickle-shaped and, as shewn in PI. 

 47, fig. 5, have their convex edge directed nearly straight for- 

 wards, and their concave or cutting edge pointed backwards. 

 Their form differs somewhat in the different species, and, as will 



