508 Dr. A. Alcock— /I neoinio 



LVir. — A Revision of the " Genus " Peneus^ ivith Diafjnoses 

 of some new Species and Varieties. By A. Alcock, M.B., 

 LL.D., F.R.S. 



Contents. 

 I. Tntroduction. 

 II. Definition of the Maniple Perifus. 



III. Diagnoses of the constituent Genera and Tables of the Species of 



the several Genera. 



IV. Diafynoses of Nine new Forms. 



I. Introduction. 



The " genus *^ Peneus (type P. monodon) was established 

 in the year 1798 by Fabricius for three species from the 

 "Indian Ocean/' one of which (P. planicornis), since its 

 antennular flagella are described as compressed^ should, 

 perhaps, be translated to the genus Solenocera of Lucas 

 (Ann. Soc. Entom. France, 2 ser. vol. viii. 1850, p. 219). 



Milne-Edwards (Hist. Nat. Crust, ii. 1837, pp. 411-418) 

 deals critically with eleven species wliich he assigns to 

 Peneus ; but two of them liaA'e since been transferred to 

 Solenocera, a genus with which we are not now concerned. 



In 1881 in these 'Annals' (vol. viii. ser. 5, p. 169) Spence 

 Bate published, along with a preliminary notice of the 

 'Challenger' Peneidse, an account of the results of an 

 examination of Milne-Edwards's types. In this paper the 

 '' genus '' Peneus is left intact, except that certain forms 

 with long antennular flagella are referred to as Peneopsis, a 

 MS. name.of A. Milne-Edwards. Peneopsis was not properly 

 characterized, nor has its type (P. serraUi) ever, as far as I 

 can ascertain, been described ; but if the two species — one 

 of which boie A. Milne-Edwards's MS. label "Peneopsis 

 ocularis " — described under this name by Faxon (Mem. Mus. 

 Comp. Zool. Harvard, xviii. 1895, p. 187) may be taken as 

 typical of the genus, then Peneopsis diflPers from all Penei 

 and agrees Avith all Peneinae except Peneus in having two 

 arthrobranchise on the penultimate pair of legs. So that 

 Peneopsis, like Solenocera, may be left out of consideration 

 in a review of the phratry or maniple Peneus. 



In 1885 S. I. Smith (Proc. U.S. Nat. Mus. viii. p. 170) 

 proposed to I'cstrict the name Peneus to those species in 

 which (1) the endopodite of the maxillules is elongate and 

 segmented, (2) the third maxillipeds have an epipodite, and 

 (.'3) tlie last thoracic somite carries a pleurobranch. To the 



