MONOGRAPH OF THE GENUS PERIPATTJS. 445 



organs of touch, similar to those in other parts of the skin, 

 having their projecting portions enclosed in delicate spines 

 formed by the cuticle. The skin of the lips is raised into a 

 series of papilliform ridges, whose general form is shown in 

 fig. 5 ; of these there is one unpaired and median behind, and 

 a pair, differing somewhat in character from the remainder, 

 in front, and there are, in addition, seven on each side. The 

 cutaneous papillae round the front of the lips are raised up 

 and appear like a second outer lip concentric with the anterior 

 part of the real lip, with the posterior part of which it is 

 continuous. 



The structures within the buccal cavity are shown as they 

 appear in the surface views in fig. 5. In the median line of 

 the buccal cavity in front is placed a thick muscular protuber- 

 ance, which may perhaps conveniently be called the tongue, 

 though attached to the dorsal instead of the ventral wall of the 

 mouth. It has the form of an elongated 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. 



The Jaws. — On each side of the tongue are placed the 

 jaws, which are a pair of appendages, modified in the character- 

 istic arthropodan manner, to subserve mastication. They are 

 essentially short papillae, moved by an elaborate and powerful 

 system of muscles, and armed at their free extremities by a 

 pair of cutting blades or claws. The latter structures 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. They are sickle-shaped, and, as shown in fig. 5, 

 have their convex edge directed nearly straight forwards, and 

 their concave or cutting edge pointed backwards. The inner 

 cutting plate has five to eight teeth (fig. 27). The outer plate 



