A REVISION OF THE BRITISH IDOTEID^. 727 



Zenobiana, Stebbing. Bate and Westwood were evidently of this opinion, for 

 writing in 1867 (3) they stated: "This species [Idotea par allela = Zenobiana 

 prismatica (Risso)] appears to us to be very closely allied to, if not identical with, 

 the genus Cleantis of Dana." 



Miers (44) in his "Revision" states that Leach's diagnosis of Stenosoma "does 

 not permit of its being used for a sectional designation. . . . Leptosoma, on the 

 other hand, will include all Idoteae with a uniarticulate postabdomen." This author, 

 however, overlooked the fact that Risso's name Leptosoma was preoccupied. 



Leach's original diagnosis of Stenosoma (41, p. 365) is as follows: — "Antennae 

 exteriores corporis longitudine, articulo tertio quarto longiore. Corpus lineare." 



He included in this genus two such dissimilar species as his hectica ( = Idotea 

 linearis (Pennant)) and acuminata ( = the Stenosoma acuminatum, Leach). 



The fact that Say (65), when describing his jiliformis ( = Erichsonella jiliformis) , 

 included it in this genus, Gould (26) his Idotea irrorata, and Dana (17) his Idotea 

 gracillima, sufficiently illustrates how imperfect the diagnosis is. The name has 

 been used with so many varied conceptions that, with Miers, I agree that it cannot 

 be employed for any section or division of the family. 



Seeing that neither of the above names can be employed, I am proposing that 

 of Synisoma, and give an emended diagnosis of the genus. 



Synisoma, it may be remarked, differs from the genus Erichsonella of Benedict 

 in the following characters : — 



1. The flagellum of the antennae does not consist of only a single clavate joint. 



2. The coxal plates are distinctly separated and visible dorsally on all excepting 



the first segment. 



As pointed out above, Racovitza and Sevastos have already separated the 

 genera Mesidotea, Richardson, Chiridotea, Harger, and Proidotea, Rac. andSev.,and 

 placed them in the sub-family Mesidoteinae. The remaining genera fall into at 

 least three or four further subfamilies, of which the Idoteinae of Miers would contain 

 the genus Idotea, Fabr., and allied genera. 



Barnard (Ann. Sth. Afr. Mus., 1914, p. 203) has recently described the new 

 genus Engidotea, with the /. lobata of Miers as the type, which species is charac- 

 terised by the inner lobes of the first maxillae having only two setose spines, the 

 second maxillae having only two lobes, and no setose styles on the uropoda. The 

 palps of the maxillipedes are five-jointed. 



IV. Geographical Distribution. 



Whilst members of the Idoteidae are found in all parts of the world, they would 

 seem to be more numerous in the temperate and colder seas than elsewhere. Many 

 species are found on the shore and in shallow water, whilst others frequent moderate 

 depths, and a few have been taken at considerable depths. Harger (30) records 



