ISOPODA OP THE 'LIGHTNING' AND OTHER EXPEDITIONS. 121 



at the side of and underlying the telson, is here so articulated that it more or less 

 arches over and partially conceals the telson ; the inner branch consists of two broad 

 joints and underlies the telson. It is to the fancied resemblance of this peculiarly 

 constructed tail to the opening of the petals of a flower that we owe the name of the 

 genus, Anthura {av6oc„ a flower; ovpa, a tail). Bate and Westwood, remarking on the 

 structure, write : — " The apparatus when open forms a concave cup-like disc ; and 

 when at rest, from being affixed vertically, the outer plate falls back and shuts down 

 upon the dorsum of the middle tail-plate, like the two wings of a closed triptych." 



Synopsis of Genera of Anthuridse. 



Section A. Labium terminating in two rather broad rounded lobes. Mandibles 

 having the jaw furnished with a somewhat falcate projecting process 

 below, well arched and terminating in two or three blunt inconspicuous 

 teeth above ; a thin blade with semicircular saw-toothed edge unites the 

 falcate process below and the arching termination of the mandible above ; 

 this blade, when highly magnified, is seen to have a serrated edge : the 

 serrations are usually few, about five, but in the genus Cyathura they 

 are very numerous, and here the general appearance reminds us strongly 

 of an arc of a circular saw. First maxilke simple, without exterior limb 

 or palp, subpyriform; rounded below, then gradually tapering, but ulti- 

 mately sHghtly expanding and bending forwards, terminate in con- 

 spicuous and well-developed teeth. Second maxillfe without palp, 

 with the distal extremity sliglitly cleft. Maxdlipeds consisting of two 

 to five joints, which are broad and flattened. 



1. Five earlier segments of pleon coalesced into a single segment in 



female, distinct in male. Flagella of antennae of both pairs in female 

 few-jointed, of upper pair in male greatly developed and multiarticu- 

 late. Maxillipeds two-jointed Anthura, Leach. 



2. Five earlier segments of pleon coalesced into a single segment (at least 



dorsally) in the female. Flagella of antennse of both pairs rudi- 

 mentary (that of the upper pair in the male not greatly developed ?). 

 Maxillipeds three-jointed Cyathura ', n. g. 



3. Segments of pleon very short, but distinct in female. Flagella of 



antennae of both pairs many-jointed, of upper pair in the male 

 developed into a remarkable brush-like organ nearly equal in length 

 to half that of the animal, and composed of very numerous, short, 

 broad, and densely ciliated joints. Maxillipeds five-jointed, second 

 joint very short Anthctura', n. g. 



4. Segments of pleon quite distinct and fully half as long as broad; 



pleopods alike, the first pair not covering or concealing any of the 



' Kvatios, a cup, and ovpu, a taiL 



^ atdiiXii, a blossom, and ovpa, a tail. 



