162 grosse's classification and 



chitinous margins bearing small bristles. The labrum of the 

 PhilopteridcB. has a broad disc-like basis fixed on the under side of 

 the head; and is divided by some transverse furrows (Figs. 2, 3, 5, 

 lb.) There is a broad furrow, separated from the mouth by a 

 plate of chitin, and farther forward a deep narrow furrow, next the 

 anterior boundary of the labrum. In the living animal the 

 labrum is constantly moving ; and in PniLOPTERiDiE it can adhere 

 to glass like a suctorial disc. The labrum can thus hold on to 

 hairs or feathers. 



Mafidibles. — As a type, we take the mandibles of Tetroph- 

 thalmus (Fig. 4). They have each two strong, long teeth, some- 

 what different in their structure. 



The under tooth of the left mandible has a protuberance with 

 curved point and an arched surface ; its upper tooth has two 

 points. The right mandible has two stout teeth, which fit the left 

 mandible on closing. This serves for cutting particles held 

 between the labrum and the first maxillae. The large pointed 

 teeth serve for removing dermal scales. The mandibles of the 

 Philopterid^ are long, triangular, and two-toothed, the teeth 

 short and thick (especially in genus Docophorus). 



First maxiU(B. — These are conical, and have a basal and a 

 terminal segment or blade, distinguishable in young specimens. 

 The inner side of the blade has booklets (not in Docophoriis\ 

 (Figs. 5, 6). The maxillse seem to take no part in comminuting 

 the food beyond aiding in its prehension. With all care Grosse 

 has never been able to find the palps of the first maxillae which 

 Nitsch ascribes to Liotheid.e. Nitsch figures them in Trinotum 

 conspurcatum^ but this can scarcely be correct, for he places the 

 four-jointed papillae on the blade near its anterior border. In 

 Tetrophthalmus the palps belong not to the first but to the second 

 maxillae. The same is true of MenopoJi pallidum, Colpocephalum 

 zebra, a Laemobothrium from Gypogera?ius serpentarius, and a 

 Trinotum from the swift, and probably is the case with all the 

 genera and species. 



Second maxillce (unterlippe). — These are flat, fused, bounding 

 the mouth posteriorly. They consist, in LiOTHEiDiE, of two parts, 

 which are united by a transverse fold (Fig. 8). The basal part 

 (mentum, mt,) represents the coalescing stipites and squamse of 



