rnRONiMiD^. 319 



angle on each side. Percion having the first two segments fused 

 together. Mandibles without an appendage. Eyes large. Su- 

 peiior antcnntc rudinientaiy ; interior antenna; obsolete. Gna- 

 thopoda small, not subchelate. First four pairs of pereiopoda con- 

 sisting of but six joints, the terminal one probably being the pro- 

 podos and daotylos fused together ; carpi dilated : fifth pair not 

 developed from the bases. Three posterior pairs of pleopoda single- 

 branched, uniarticulate, membranous, lamelKform. Telson single, 

 membranous. 



Risso says that these Cnistacea are eaten as a luxuiy, and, more- 

 over, serve as an article of food to the inhabitants on the shores of 

 the Mediterranean, where they are most common. 



1. Phrosina semilimata. (Plate LI. fig. 5.) B.M. 



Plirosina seiiiiluuata, lii.'iso, Journ. de Physique, p. 245, 1822 ; Hist, 

 dc rEuropc Jlcrid. p. 5. pi. ,3. f. 10-12. 



Pleon exhibiting traces of a dorsal carina ; fourth segment produced 

 to a distinct tooth. Eyes pressed towards the inferior margin of 

 the cephalon. Supez-ior antennae rudimentary, consisting of one 

 short basal and a longer terminal joint, situate beneath the horns 

 of the semilunar notch: inferior antennae obsolete. Mandibles 

 having the incisive margins evenly corrugated, flanked by a strong 

 tooth on each side ; the molar tubercle developed into a large 

 squamiform perpendicular plate fringed with hair. Gnathopoda 

 subcqual, small, slender, not subchelate. First pair of pereiopoda 

 nearly as long again as the gnathopoda, having the ischium antero- 

 distally produced to a strong tooth ; meros likewise so produced ; 

 carpus subtriangular, antero-inferior margin obtusely serrated, in- 

 ferior angle developed into a strong tooth-like process ; propodos 

 and dactylos fused together, long, tapering, and slightly arcuate. 

 Second pair of pereiopoda like the fii-st, but having the inferior 

 distal angle of the meros produced to a sharp tooth ; carpus broad, 

 tapering, armed inferiorly with strong, sharp teeth. Thii-d pair 

 longer than the second, having the basos anteriorly dilated ; meros 

 dilated, postero-distally produced to a long sharp process ; carpus 

 ovate, not produced postcro-distally to a long tooth, anteriorly 

 deeply denticulated ; proi)od()s and dactylos fused into one long, 

 slightly-cur\'ed styliform organ. Fourth pair like the third, but 

 shorter and less conspicuously characteristic. Fifth pair having 

 the coxa rudimentaiy ; the basos large, ovate ; the rest of the 

 joints obsolete, being represented only by a small ])a])illa. Three 

 posterior paii's of pleopoda without peduncles, consisting of single, 



