M. E. Hesse on the Pranizae and Aneei. 409 



tached to a common peduncle. Besides the branchial feet, the 

 sixth segment presents on each side, near its antero-lateral 

 angles, a false foot with a very short basal joint, and with two 

 terminal lamin8e extended horizontally in the form of a caudal 

 fin. In the young, the abdomen is generally nearly as broad 

 as the thorax, and presents no constriction either at base or 

 apex: 



Structure of the Pranizae at the period of their transformation 

 into Ancei. 



After their attaining the form just described, the Praniza 

 undergo little modification of form : the antennae, thoracic feet, 

 and abdomen scarcely change; but the head and thorax are 

 subject to some modification. 



The head is remarkably small, distinct from the body, trian- 

 gular in form, globular above, flattened below, and incurved at 

 the apex. Seen from above, it appears to be clearly divided into 

 three parts — namely, the extremity of the rostrum, the rostrum, 

 and the forehead. The apex of the rostrum is conical and 

 acuminated ; it is formed by two mandibles, which are pointed, 

 denticulated within, and incurved. The rostrum is enlarged in 

 the middle, and narrowed towards its junction with the forehead, 

 from which it is separated by a straight raised line, the extre- 

 mities of which reach the base of the antennae. The rostrum is 

 traversed vertically by deep lines or grooves, indicating the union 

 of five pieces ; and besides these there are two lateral ones which 

 embrace the former, and are soldered to them at the base, but 

 free at the apex, which is pointed and recurved ; from within 

 these two laminae issue the styles with denticulated apices, which 

 are seen at each side of the extremity of the rostrum. 



The antenna (already described) are inserted at the base of the 

 rostrum, in a notch which presents a rounded process ; this is 

 the auditory tubercle : the skin covering its extremity presents a 

 sort of very close network formed of crossing lines. 



The eyes are large and prominent, hemispherical, and com- 

 posed of round facets ; they are placed obliquely on the sides 

 of the head. The neck presents three folds. 



Seen from beneath, the head presents the same threefold divi- 

 sion : the apex has nothing remarkable about it ; but the two 

 other parts contain the buccal apparatus. The mouth is closed in 

 front by the first pair of /oo//aw;s, consisting of the inner branch, 

 which is lamellar, notched at the apex, and terminated by two 

 blunt points furnished with hairs. These footjaws have no palpi ; 

 their outer margins appear to be attached to the head in the 

 manner of a hinge, as in the Ancei. The second and third pairs 

 of footjaws, covered by those just described, form denticulated 



