248 



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

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



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

 by the follovving key. 



Key to the genera of Crangonidae. 



a x Peraeopods of 2 nd pair present. 

 ó 1 Peraeopods of 2 nd pair chelate. 



c x Fourth and fifth pairs of peraeopods having the seventh 

 joint not dilated, not natatorial. 

 d y Peraeopods of 2 nd pair subequal in length to the rest. 



e x Carapace without strong sculpture Crangon Fabr. 



f x An arthrobranch present at base of third maxillipeds Subgenus Crangon Fabr. 

 f„ No arthrobranch at base of third maxillipeds . . Subgenus Notocrangon Cout. 

 e, Carapace with very strong sculpture. 



No arthrobranch at base of third maxillipeds. . . Sclerocrangon G. O. Sars 

 d„ Peraeopods of 2 nd pair much shorter than the rest. 

 e x 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 Guér.-Ménev. 



£ 3 Fourth and fifth pairs of peraeopods having the seventh 



joint dilated, natatorial Argis Kröyer 



b % Peraeopods of 2 nd pair simple, non-chelate. 



Cy Eyes well-developed. (In Naushonia the cornea is repre- 

 sented by a minute pigment spot.) 

 d x Carapace without "linea thalassinica". Mandibles without 

 palp. 

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



minating in a distal spine . Sabinea Owen 



e„ Antennal scale short, feeble, subtriangular, without 



distal spine Vercoia Baker l ) 



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



e v Mandibles simple, palp three-jointed Coralliocrangon Nobili 



e, Mandibles excavate, with dentate incisor and blunt 



molar process; palp two-jointed . Naushonia Kingsley 



c a Eyepeduncles transformed into a pair of trihedral processes, 



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

 a. 2 Peraeopods of 2 nd pair wanting Paracrangon Dana 



1) 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 Salii/iea Owen. 



