277 



This species has been long known only by Stimpson's original diagnosis, until de Man 

 gave a very elaborate description. In Stimpson's posthumous paper a useful figure of the 

 whole animal is to be found. Hab. east coast of Nippon, in 30 fathoms. De Man gives as 

 locality : "Inland Sea of Japan, in deep water". 



2. Asthenognathus hexagonum Rathbun. 



1909. Asthenognathus hexagonum Rathbun. Proc. Biol. Soc. Washington, v. 22, p. iii. 



1910. Asthenognathus hexagonum Rathbun. K. Dansk. Vid. Selsk. Skr., 7. Raekke, Afd. 5, 



n° 4, P- 339. Pl- 2, f. 14, textfig. 24. 



Hab. Gulf of Siam. 



Tritodynamia Ortmann. 

 1894. Tritodynamia Ortmann. Zool Jahrb., Syst., Bd. 7, p. 692. 



Ortmann referred his genus to the Hexapodinae, chiefly on account of the considerable 

 reduction of the last pair of legs. De Man, in describing Asthenognathus inaequipes^ remarked 

 that the present genus might belong to the Asthenognathinae. Yet Miss Rathbun, (1. c, 19 10, 

 p. 340), who simply unites Tritodynamia with Asthenognathtts, in my opinion goes too far, 

 for the insertion of the dactylus of the external maxillipeds is different in both genera, as has 

 been proved by Nobili. 



This latter author, in adding to the type species, T. japonica Ortmann (1. c, p. 693, 

 pl. 23, f. 5) a new one, T. horvdtlii (Ann. Mus. Hung., v. 3, 1905, p. 407, pl. 10, f. i), 

 sharply discriminates the two species, so that a reference to his paper may suffice. The genus 

 is only known from the coasts of Japan. 



Mortensenella Rathbun. 



1909. Mortensenella Rathbun. Proc. Biol. Soc. Washington, v. 22, p. iii. 



Miss Rathbun referred her genus to the Pinnotherelinae, but on account of the shape 

 of the external maxillipeds, the palp of which is very small and not broadly expanded, (ischium 

 and merus subequal and separated by a faint suture) I prefer to range it among the present 

 subfamily. It is remarkable that the chela of the only species known much resembles that of 

 Tritodynamia horvdthi Nobili. The genus is founded on M. forceps Rathbun (see K. Dansk. 

 Vid. Selsk. Skr., Afd. 5, n" 4, 1910, p. 337, pl. i, f. 18, textfig. 21), which inhabits the 

 Gulf of Siam. 



Hapalonotus Rathbun. 



1879. Alalacosoma de Man. Notes Leiden Mus., v. i, p. 6j (praeocc). 

 1897. Hapalonotus Rathbun. Proc. Biol. Soc. Washington, v. 11, p. 164. 



The name Hapalonotus has been proposed by Miss Rathbun in order to replace 



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SIBOGA-EXPEDITIE XXXIX 6'. ' 36 



