8 



P. canaliculatus. 



P. semisulcatus. 



In addition to the Indian forms hereafter specified, I have examined the 

 following species :— P. caramote, P. australiensis, P. latisulcatus, P. brasiliensis, 

 P. setifer, P. s tylirostris. 



Key to the Indian species of the genus Peneus {sensu restricto). 



I . Telson with three spinules in the distal half of each border: carapace with 

 three median longitudinal dorsal grooves— one of which is excavated 

 in the post-rostral crest— all extending nearly up to its posterior 

 border ... 

 II, Telson without marginal spinules : the three median dorsal grooves, if 

 defined, never reach to the posterior border of the carapace : — 



1. Exopodite of last pair of thoracic appendages absent or quite 



vestigial : a longitudinal post-antennal *suhhepatic crest 

 near the antero-lateral angle of tVie carapace ... 



2. Exopodite of last pair of thoracic appendages small but well 



formed : — 



i. An oblique post-antennal subhepatic crest near the 

 antero-lateral angle of the carapace : upper anten- 

 nnlar flagellum not longer than its peduncle 

 ii. No subhepatic crest on the carapace : upper antennular 

 flagellum a good deal longer than its peduncle : — 

 a. Dactylus of external maxillipeds of adult 

 male about as long as the propodite : 

 rostral crest, in both sexes, of only 

 moderate height 

 6. Dactylus of external maxillipeds of adult 

 male hardly half the length of the propo- 

 dite : rostral crest conspicuously high 

 and of a broadly triangular form in both 

 sexes 

 c. Dactylus of external maxillipeds of male 

 from 1| to 2f times the length of the 

 propodite : rostral crest high, but not 

 forming a decided triangle ... 



P. monodon. 



P. indicus. 



merguietisis. 



P. penicillatus. 



1. Peneus monodon, Fabricius, Bate. Plate I., fig. 1, la-b. 



f Penseus monodon, Fabricins, Entomol. Syst., Suppl., p. 408, 1798: ? Bosc, Hist. Nat, Crust. II. p. Ill, 1802 : 

 ? Latreille, Hist. Nat. Crust. VI. p. 24,9, 1803 : ? Lamarck, Hist. Nat. Anim. sans Vert. V. p. 206, 1818 : ? Deamareat, 

 Coiisid. Gen. Crnst., p. 225, 1825: Milne Edwards, Hist. Nat. Crnst. II. p. 416, 1837:? Kraass, Sadafr. Croat. 

 p. 55, 1843: Stimpson, Proo. Acad. Philad. 1860, p. 44 : Heller, Novara Crust., p. 122, 1865. Spence Bate, Ann. 

 Mag, Nat. Hist, (5) VIII. 1881, p. 178, and Challenger Macrura, 1888, p. 250 (part.) pi. xxiv. fig. 1 : Haswell, Cat. 

 Anatral. Crnst. p, 199, 1882 : ? Miers.P.Z.S,, 1884, p. 15 : Henderson, Trans. Linn. Soc. (2) V, 1893, p, 447 (part.) 

 ? Ortraann in Semon'a Zool. Forachnngsr. in Austr. u.d. Malay. Arch., 1894, p. 9 : ? de Man, Zool. Jahrb., Syst. X. 

 1898, p. 677 : Doflein, Abh. bayer. Akad., Miinchen, XXI. iii. 1902, p. 632 : ? Nobili, Boll. Mus. Torino, XVIII. 

 1903, No, 452, p, 1 : ? Stebbing, Mar. Inv. S. Afr., Crnst. III. 1905, p. 74. 



* The subhepatic crest (truly poat-antennal in position) which is present only in P. japonicus, semindcatus 

 and monodon, is not to be contused with the strong oblique post-antennular crest (running from the so-called 

 '' anlennal supine ") which is present in all the species. 



