BORRADAILE— ON THE PONTONIIN^ 389 



5. AncMstus mirabilis (Pesta), 1911. 



Marygrande mirabilis, Pesta, Zool. Anz. xxxviii. p. 571. 

 Samoa, in Tridacna gigas. 



6. Anchistus (?) armatus (H. M.-Edwards), 1837. 



Pontonia armata, H. M.-Edwards, Hist. Nat. Crust, ii. p. 359 (1837). 

 Anchistus (?) armatus, Borradaile, Ann. Mag. Nat. Hist. (7) ii. p. 387 (1898). 

 New Zealand. 



Genus Pontonia Latreille, 1829. 



Cuvier's R. An. 2nd ed. iv. p. 96. Roux, M^m. s. les Salicoques, p. 26 (1831). 

 H. M.-Edwards, Hist. Nat. Crust, ii. p. 358 (1837). De Haan, von Siebold's Fauna 

 Japonica, Crust, p. 175 (1850). Dana, U.S. Explor. Exped. Rep. xiii. i. p. 570 (1852). 

 Kingsley, Proc. Ac. Philadelphia, 1879, p. 422 (1880). Joliet, Arch. zool. exper. x. 

 p. 19 (1882). Carus, Prodr. Faun. Medit. i. p. 475 (1885). Borradaile, Ann. Mag. Nat. 

 Hist. (7), ii. p. 388 (1898). Ortmann, Bronn's Thierreich, Arthropoden, v. ii. p. 1131 

 (1899). Rathbun, Bull. U.S. Fish Comm. xx. ii. p. 121 (1901). 



Definition : Body stout, swollen, somewhat depressed ; sixth abdominal segment not 

 elongate ; rostrum short, depressed, curved downwards, not dentate, with or without 

 a keel below at the free end ; eye more or less reduced, outer flagellum of antennule 

 not deeply cleft ; antennal scale broad ; mandible without palp ; inner lacinia of maxillule 

 very broad and hairy ; second maxilliped without podobranch, with last joint mediad 

 of preceding joint ; third maxilliped without arthrobranch and with all joints broad, 

 but the widest surface of the last two in a different plane from that of the ante- 

 penultimate, so that they are apt to appear narrow ; legs stout, directed outwards, the 

 second pair with heavy chela, the last three with dactylopodite nearly straight, simple, 

 and without basal protuberance. 



Key to the species of Pontonia : 



I. Rostrum reaches at least to middle of second joint of antennule. 



A. Last three legs end in simple claw. Southern species. 



1. Rostrum outreaches antennular stalk. Dactylopodites of last three legs 



strong. Second legs subequal and similar. 

 P. minuta Baker, 1907. 



2. Rostrum ends at middle of second joint of antennular stalk. Dactylopo- 

 dites of last three legs weak. Second legs unequal and unlike. 



P. pinnce Ortmann, 1894. 



B. Last three legs end in double claws. Northern species. 

 1. Rostrum very narrow throughout. W. American. 



P. californiensis Rathbun, 1902. 



