M. E. Hesse on the Pranizae and Ancei. 41 1 



rctemble the curved scissors used by surgeons. These organs 

 resemble the mandibles of insects, and appear to perform the 

 same functions. The head, which is of a quadrilateral form, is 

 divided into four equal parts by depressed lines which cut each 

 other at right angles ; the forehead is armed with three teeth, of 

 which the middle one is generally small, acute or denticulated, 

 and the lateral ones truncated at the apex and placed within 

 the bases of the mandibles. In some species the middle tooth 

 is notched in the centre, and its points are obtuse. 



The eyes are smaller and much less prominent than those of 

 the Praniza ; they are composed of round facets, and placed at 

 the base of the antennae. 



Seen from beneath, the head is entirely occupied by the buccal 

 apparatus, which is completely covered by the two footjaws of 

 the first pair : these are lamellar, triangular, slightly convex, 

 denticulated, and ciliated on the rounded interior margin. 

 These two plates, which present a small notch at the apex, in 

 which is inserted a small, oval, ciliated, palpiform appendage, 

 lie over each other in the middle, leaving a considerable free 

 space at their base and apex ; they are attached at their base 

 by a hinge, upon which they turn so as to open downwards ; 

 they are enclosed laterally by the projecting frame of the buccal 

 apparatus. The footjaws of the second pair consist of three or 

 four Hat joints, diminishing in size from the base to the apex; they 

 are destitute of both palpus and Hagellum, and vary according to 

 the species. Within these parts there is an apparatus the nature 

 of which the author has been unable to ascertain with certainty: 

 at the highest part, in the median line, is a round orifice, which 

 may be a sucker; below this is a sort of crescent -shaped aperture, 

 then another round orifice accompanied by small acute jaws, and 

 lastly a vertical aperture margined with a sort of lip. These 

 parts are very difficult of detection. 



To the base of the buccal apparatus are attached three ciliated 

 lamellar appendages, the median one triangular and covering 

 the two others, which are rounded m form. These three laminae, 

 which have some relation with the lamellar footjaws of the £pi- 

 carides, have for their function to convey to the mouth, with the 

 water which they set in motion by their constant agitation, the 

 small objects which serve as the nutriment of these Crustacea ; 

 these pass through the interval at the base of the tirst pair of 

 footjaws. 



In the Ancei the first two thoracic segments become intimately 

 united with the head ; the tirst two pairs of feet accompany them, 

 and the cephalothoracic portion thus formed is separated by a 

 considerable constriction from the three narrower thoracic seg- 

 ments which follow, each of which bears a pair of legs. 



