Classijication of the Decapod Crustaceans. 479 



II. Third maxillipecls almost completely cover 

 the mouth. Inward oponiugs to the gills 

 may or may not be near the base of the 

 chelipeds Tymolince, 



Key to the SuperfamiUes of the Dromiacea. 



I. Sternum of female with longitudinal grooves. 



Vestiges of sixth abdominal limbs usually 

 present. Gills 14-20 on each side. Eyes 

 usually completely sheltered by orbits when 



retracted. No linea homoliccc Dromiidka. 



II. Sternum of female ■without longitudinal 

 grooves. No vestiges of sixth abdominal 

 limbs. Gills 8-14 on each side. Eyes in- 

 completely or not at all sheltered by orbits 

 when withdrawn against the body. Linece 

 homolicce usually present Homolidea. 



Key to the Families of the Dromiidea. 



I. No vestige of sixth abdominal limbs. Cara- 



pace longer than broad, with ill-marked 

 side-edge. [First three legs with mastigo- 

 branchs, fourth and hfth small, subdorsal, 

 and prehensile.] Homolodromiidse. 



II. Vestiges of sixth abdominal limbs present 



(except in Hypoconchu, where also no 

 mastigobranchs). Carapace usually not 

 longer than broad, with well-marked side- 

 edge. 



A. Mastigobranchs on first legs (chelipeds) 



only or on none. Fourth and fifth legs 



small, subdorsal, and usually prehensile. . Dromiidae. 



B. Mastigobranchs on all the first three pairs 



of legs. Fifth legs only small and sub- 

 dorsal Dynomenidae. 



Key to the Families of the Homolidea. 



I. Gills 13 or 14 on each side. Mastigobranchs 

 on first one or three pairs of legs. First joiut 

 of eye-stalks not much longer than second . Homolidae. 



II. Gills 8 on each side. Mastigobi-anchs not 



found on any legs. First joint of eye-stalks 



much longer than second Latreiilidae. 



Key to the SuperfamiUes of the Brachygniitha, 



I. Fore part of body narrow, usually forming a 



distinct rostrum. Body more or less trian- [(Maiidea). 



gular. Orbits generally incomplete Oxyrhyncha 



II. Fore part of body broad. Rostrum usually 



reduced or wanting. Body oval, round, or [(Cancridea). 



square. Orbits nearly always well enclosed. Brachykiiyncha 



