51 



has advanced the opinion that another species, established by the same author from 

 a fragment of a specimen, may also require to be transferred to a new genus. 



Gen. GnatMa, Leach, 1814. 



Syn: Anceus, Eis.su (male). 

 ,. Praniza, Latr. (larva). 



Generic Characters. Body in male subdepressed, and more or less di- 

 lated in front, with the cephalon very large, subquadrangular, and flattened ante- 

 riorly, inesosome divided by a more or less conspicuous constriction into 2 sections, 

 the anterior comprising 2, the posterior 3 well-developed segments, the foremost 

 rudimentary segment being consolidated with the head, the hindmost received 

 between the projecting lateral parts of the 5th segment. Body in female and 

 larva more or less fusiform, with the cephalon rather small, and some of the 

 segments of mesosome fused together. Metasome in both sexes, as also in the 

 larva, much narrower than the mesosome, sublinear in form. Eyes, when present, 

 placed laterally. Antennas comparatively short and subequal in length, both pairs 

 with distinctly denned flagella. Mandibles in male of different form ind the 

 different species, more or less flattened, forceps-like. Maxillipeds without epignaths, 

 masticatory lobe simple, palp consisting of 4 flattened joints fringed outside with 

 strong plumose seta. 1 ; those in female much smaller, but of a similar structure. 

 Oral parts in the larva combined into a rostrum-like cone projecting in front, and 

 in a great measure styliform. Gnathopoda in male forming a pair of very large 

 curved plates arching over the lower face of the cephalon, and terminating in a 

 small apical joint; those in female much smaller and more pediform, being divided 

 into 3 or 4 joints, and having at the base a thin lamella. IVreiopoda subeqiial and 

 of normal structure. Pleopoda with the rami uni-articulate, tipped with long seta 1 , 

 or quite, naked (in the adult animal). Uropoda with both rami lamelliform, snhe- 

 qual, and edged with slender bristles. 



Remarks. This genus was established as early as in the year 1814 by 

 Leach under the above name, which, according to the rules of priority, must be 

 preferred to the more generally used terms Anceus (the male) and /'ranita (the 

 larva). To the French zoologist, E. Hesse, is due the merit of first having made 

 out precisely the true relationship between the male, female, and larva, which had 

 not formerly been fully recognized, though Leach had already conjectured, that the 



