1887.] 



ON CTCLESTHERIA HISLOPI. 



37 



with the inferior edge of the head. The contrary movement, 

 whereby it is thrown back and closely applied against the masti- 

 catory parts of the mandibles (see Pl. III, fig. 5, L) would seem 

 to be effected by some of the transverse muscles located within 

 the body of the lip and continued some distance anterior to its 

 base. 



Movements of the Mandibles. — These are of two kinds, 

 viz , an adductive and a rotatory. The adduction of the man- 

 dibles, whereby their molar surfaces are brought into close contact 

 with each other, is performed by the powerful muscles filliug 

 up the concavities of their bodies. and all originating from a 

 lamellar chitinous tendon traversing the lower part of the man- 

 dibular segment ; by the relaxation of these muscles the molar 

 surfaces again become separated. .The rotation of the mandibles. 

 effected by the aid of the two above-described muscles joining 

 their bodies on each side from above, consists in a partial revolv- 

 ing of the mandibles forward and backward, the latter movement 

 being by far the stronger. By this revolving motion the molar 

 surfaces of the mandibles. when closely applied together by the 

 aid of the adductor muscles, perform a more complete tritura- 

 tion of the food contained between them, being forcibly rubbed 

 against each other. 



Movements of the Maxilhr. — Of the two pairs of maxillæ it 

 is in particular the first pair that show a dis tinet movement. whereas 

 the second pair would seem to have very little if any mobility. 

 Ob the former, as above stated, the terminal lamelliform part. 

 or masticatory lobe, is very movably connected with the basal part. 

 and admits. by the aid of a distinct fan-shaped bundle of very 

 short muscles that join it at the base (see Pl. IV. fig. 5). of being 

 doubled upon the inner side of the basal part, whereby the 

 comb-like bristles on the edge of this lamella are push ed forward 

 against the oral orifice. A very thin muscle is found too 

 joining the basal part of both pairs of maxillæ from without, 

 thus indicating a slight mobility also of that part. 



Movements of the Legs. — These movements. as in other 

 Phyllopoda, are very peculiar and performed in a perfectly rhyth- 



