THE 5I0UTH-PARTS. 65 



as, for instance, by V. Siebold in his * Anatomy of the 

 Invertebrata.' 



In my first communication on this subject to the 

 Linnean Society (February, 1862) I described the 

 mouth parts as follows: — 1st, an upper lip; 2nd, a 

 pair of mandibles ; 3rd, a pair of maxillfB ; 4th, a pair 

 of small palpi ; 5th, a pair of organs probably homo- 

 logous with the second maxillge ; 6th, a central organ, 

 corresponding to the so-called " langue vesiculeuse " in 

 the Lepismidce ; 7th, the lower lip. 



Taking Tomocerus as a typical species, the labrum, 

 (PL LXIV, fig. 4.) is a simple, entire, quadrate, horny 

 lobe, somewhat broader at the base than at the apex, 

 with a few scattered hairs, and on the front margin a 

 row of teeth or minute bristles at a little distance from 

 the free border. 



The mandibles (PI. LXIV, fig. 2) are long and 

 somewhat cylindrical, with a large gaping orifice, 

 through which the muscles pass into the head. At 

 some distance from the teeth is a raised molar surface, 

 which is covered with minute, rather blunt teeth, and, 

 in conjunction with the corresponding portion of the 

 opposite mandible, evidently serves the function of 

 mastication. The terminal incisive portion is generally 

 dissimilar in the two mandibles, the one having gene- 

 rally a tooth more than the other. This part of the man- 

 dible diminishes rapidly in thickness towards the tip. 



The maxillas (PI. LXIV, figs. 1 and 8) are a little 

 shorter than the mandibles ; they are narrowest 

 towards the upper end and widest towards the middle. 

 The upper extremity is terminated by a somewhat 

 complicated system of teeth, which appear to have some 

 power of independent movement. The body of the 

 maxilla is strengthened by a chitinous framework; 

 down each side runs a strong rib, while the two are 

 connected at the centre by a transverse piece, which is 

 also continued on the inner side a little way beyond 

 the rib, and curves at the same time, so as partly to 

 smTound the softer parts. The two lateral ribs con- 



5 



