248 



Besides these two forms and the genera Sabinea Owen and Prionocrangon W.-Mas., 

 also in the genus Vercoia Baker the peraeopods of the 2°<' pair are simple, non-chelate. 



The family Crangonidae contains thus at present 1 1 genera, which may be distinguished 

 by the following key. 



Key to the genera of Crangonidae. 



a^ Peraeopods of 2"'^ pair present. 

 <Jj Peraeopods of 2°'* pair chelate. 



^j Fourth and fifth pairs of peraeopods having the seventh 

 joint not dilated, not natatorial. 

 d^ Peraeopods of 2"'' pair subequal in length to the rest. 



e^ Carapace without strong sculpture Crangon Fabr. 



/i An arthrobranch present at base of third ma.xillipeds Subgenus Crangon Fabr. 

 /o No arthrobranch at ba.se of third maxillipeds . . Subgenus NotocrangonCout. 

 e„ Carapace with very strong sculpture. 



No arthrobranch at base of third ma.xillipeds. Sclerocrangon G. O. Sars 

 rt^2 Peraeopods of 2"'' pair much shorter than the rest. 

 e^ Inferior apices of branchiae turned backwards. Bran- 

 chiae 6 or 7 in number Pontophilus Leach. 



e„_ Inferior apices of branchiae turned forwards. Branchiae 



8 in number Aegeon Guer.-Menev. 



c„ Fourth and fifth pairs of peraeopods having the seventh 



joint dilated, natatorial Argis Kroyer 



b^ Peraeopods of 2°'^ pair simple, non-chelate. 



fj Eyes well-developed. (In NausJiOfiia the cornea is repre- 

 sented by a minute pigment spot.) 

 d^ Carapace without "linea thalassinica". Mandibles without 

 palp. 

 e^ Antennal scale well-developed, the outer margin ter- 

 minating in a distal spine Sabinea Owen 



^2 Antennal scale short, feeble, subtriangular, without 



distal spine Vercoia Baker ^) 



d„ Carapace with "linea thalassinica". Mandibles with palp. 



e^ Mandibles simple, palp three-jointed Coralliocrangon Xobili 



^2 Mandibles excavate, with dentate incisor and blunt 



molar process; palp two-jointed. ...... Naushonia Kingsley 



c^ Eyepeduncles transformed into a pair of trihedral processes, 



with acute and somewhat divergent tips; eyes absent. Prionocrangon W.-Mas. 

 a^ Peraeopods of 2'^^ pair wanting Paracrangon Dana 



l) The genus Vercoia Baker is included with some doubt in this key, because the mandibles are unknown, while the author 

 did not indicate the differences from the genus Sabinea Owen. 



