M. T. Thorell on the Morphology of the Argulidse. 157 



the front, whence I conclude that both borders of the lower 

 lip have coalesced with each other in the formation of the 

 mouth-tube. Above, before the middle of the front surface, 

 two small teeth are observable. Laterally, its diameter is 

 almost the same throughout ; and the club-like shape depends 

 consequently on the fact of its being somewhat broader at the 

 extremity. The tip itself is obliquely truncated, and shows 

 behind a hood-like extension of the wall of the tube, which 

 spreads itself over the back part of the oral aperture in the 

 form of a large, moveable, almost crescent-shaped lip. The al- 

 most triangular oral aperture is bounded by the two posterior 

 (inferior) arms of an almost H- or X-shaped chitinous structure 

 or apparatus, as also by two thin, oblong, chitinous lamellae, 

 which are rounded at the extremity, and are situated immedi- 

 ately beneath these, and whose direction is parallel with them : 

 on the inner margin these latter show some few saw-like teeth. 

 Both these lamellse I regard as maxillae. 



Somewhat higher up in the tube are placed the two man- 

 dibles. They are oblong, almost triangular, somewhat curved, 

 and end on either side in a finely pointed apex, above and be- 

 fore which the convex (lower and inner) margin is raised into 

 two smaller and two stronger teeth. These mandibles are di- 

 rected with their tips towards each other, inwards and upwards, 

 in the gullet, while the maxillse diverge backwards and out- 

 wards. 



In order to give suppleness to this armature, and at the 

 same time to support the mouth-tube itself, this last contains a 

 rather complicated chitinous framework. Such a framework is 

 apparent on either side of the tube, and involved in its wall, 

 being somewhat thickened beneath the crescent-shaped lip, 

 where it forms a knob on either side of the tube. This knob 

 furnishes the principal support for the mandible. Two other 

 such chitinous processes, which are placed more inwards and 

 backwards in the tube and do not touch its walls, extend below 

 the lip, whose arch they seem to support, and form here a bow 

 by means of which they unite with the two side processes. The 

 X-shaped chitinous framework which bounds the oral aperture 

 is also brought into connexion with these processes by means 

 of its arms, and thus, at the extremity of the mouth-tube, is 

 formed a solid apparatus. 



The gullet ascends as a slender, strongly chitinous tube, and 

 proceeds backwards in a bowed shape through the nervous 

 ring situated in the throat to the stomach, where it opens, by 

 means of a remarkable cup-like organ, into a cardia or stomach- 

 mouth ("mag-mun"), which probably acts as a sucking-pump. 

 I think it probable that the maxillae serve to effect an opening 



