NEW M'ALLOPHAGA. 465 



Burgess has studied the mouth-parts of Psocus in detail, 

 and for the sake of his accounts of the forks, and of the 

 oesophageal sclerite and lingual glands, those structures 

 so characteristic of the Psocidee, and probably — certainly, 

 in the case of oesophageal sclerite and lingual glands — 

 quite as characteristic of the Mallophaga, I quote from 

 his paper referred to, as follows: — 



" The maxilla in Psocus is hinged to the head by a 

 small obscure piece which is immovably soldered to a 

 larger joint. The first piece represents, probably, the 

 cardo of a typical maxilla (plate lxiv, fig. 10, c) and the 

 second the stipes (p). The stipes bears outwardly the 

 4-jointed maxillary palpus, while inwardly is hinged a 

 thick, fleshy lobe, broad at the base, but soon contracting 

 and curving inward. The tip is flat and has a broad, 

 oval outline on the inside, and is strengthened by several 

 imbedded chitinous rods and other pieces. This lobe, 

 by its position and shape, is doubtless homologous with 

 the ordinary outer maxillary lobe, or galea, of the other 

 Orthoptera. Behind the lobe, that is between it and the 

 tongue, lies the ' horny process ' of Westwood's descrip- 

 tion, or 'fork,' as I shall call it. This is a slender, more 

 or less curved chitinous rod with a forked bifid tip, and 

 two or three times as long as the outer lobe (plate lxiv, 

 figs. 9 and 10, f). The distal portion of the fork, about 

 one-third or less of its length, projects through the lining 

 membrane of the mouth. At this point the fork is stout- 

 est, and from it, it tapers to either end, the outer portion 

 being stouter than the inner. The membrane where it is 

 united with the fork is delicate and elastic, thus permit- 

 ting the fork to be projected forward or drawn back at 

 will. Within the head the fork is held in position by 

 muscles inserted on its base, which unite it with the lobe 

 and stipes of the maxilla, and by a ligament which runs 



