Mangan — On the Mouth-Parts of some Blattidce. 3 



slender tendon on the outer edge of the jaw. Adduction or flexion is brought 

 about by two powerful muscles. The long flexor [L] is a very large muscle 

 arising from the roof and back of the head, its fibres converging to a very 

 strong chitinous tendon which is inserted on the posterior surface, close to 

 the lacinia mobilis, being therefore quite removed from the ginglymus, near 

 which it is said, by Miall and Denny, to be inserted. The short flexor (aS^) 

 arises from the crus of the tentorium, and is inserted directly upon the 

 posterior surface of the jaw. A third muscle {In), which has not been 

 recorded by the above authors, lies within the mandible, and might also 

 act as a flexor, though more probably it moves the tongue. The fibres spring 

 directly from the outer surface of the mandible and form an elongate 

 tapering bundle, which merges into a thin, round, chitinous tendon, this 

 latter passing to the side of the tongue. Basch ('65) figures a similar muscle 

 in Termes, terming it the levator linguae. 



The accompanying drawings were made from the adult male P. cmstralasice, 

 but I could detect no differences in the female, or in specimens of P. americana, 

 Blatta orientalis, or Phyllodromia germanica. The parts in a specimen of 

 B. orientalis 4 mm. in length were essentially as in the adult. 



The Hypophakynx. (Plate I.) 



The hypopharynx, or tongue {hij), though partially connected with the 

 labium, arises between the mandibles, and is best considered with them. The 

 proximal portion (hypopharynx of Huxley) is a broad fold of the hinder 

 surface of the mouth-cavity, smooth and flat. The free distal portion (lingua 

 of Huxley) tapers slightly, and presents an arched surface, densely covered 

 with hairs. The hypopharynx is strengthened basally by two chitinous plates 

 {x and y), the distal of which (y) bears a number of strong bristles, and is 

 continued along the edge of the anterior surface as a chitinous rod. In contact 

 with this laterally is situated the smaller proximal plate («), which ends 

 basally, close to the tendon of the interior muscle of the mandible. The 

 free tip is furnished at the sides with a pair of elongate plates {z), which 

 carry bristles, and are continuous behind, as thin rods, round the opening of the 

 salivary duct ; posteriorly the distal surface of the hypopharynx exhibits a 

 pair of less decided chitinous thickenings. 



The position of the above plates (s) is conformable with tlie idea that they 

 may represent a pair of maxillulte (see Hansen, '93), which have become com- 

 pletely fused with the tongue, since in the Apterygota these latter are shown 

 to originate, at least in some cases, between the mandibles. On each side a 



