730 DR WALTER E. COLLINGE. 



to twenty articulations in the flagellum of the antennae and figures eighteen. Bate 

 and Wkstwood (3) state about twenty. Miss Richardson (58) gives fourteen as the 

 number, whilst I Larger (30) states twelve to sixteen, and shows seventeen in his 

 figure (pi. v, fig. 25b). 



Both Miss Richardson and Harger in their figures of the maxillipedes show the 

 basal segment, to" which the four-jointed palp is attached, as one piece. Bate and 

 Wkstwood show it with a short lateral process on the inner side, but only figure 

 three joints in the palp. Sars shows the joint and process, but the terminal portion 

 is scarcely correct. I have elsewhere shown (13) that the oral appendages in the 

 Isopoda are liable to considerable variation, but not to the extent of the fusion or 

 total absence of the different parts. 



Numerous other instances might be quoted, for similar variations are to be found 

 in the figures of the first and second maxillse, the shape of the cephalon, the coxal 

 plates, and the uropoda, but these are sufficient to indicate how imperfectly described 

 and figured the various species are. 



No author, so far as I am aware, either describes or figures the groove on the 

 third joint of the palp of the maxillipede. A certain amount of difference may be 

 due to figuring and describing immature specimens (see p. 739), in other cases the 

 differences are possibly due to differences in the sexes, many authors not stating 

 whether the examples were male or female ; be this as it may, the need of more 

 accurate figures must have been felt by everyone who has studied the family. 



(a) General Form. 



The body is more or less broad and flattened, the various genera and species 

 ranging from an oblong oval to an elongated linear shape. There is considerable 

 range in the size of the different genera and species. The largest member of the 

 family is Glyptonotus antarcticus, Eights, which attains a length of 90 mm.,- and 

 the smallest is Idotea danai, Miers, which is only 2 mm. long. The males in 

 practically all cases are larger and more robust than the females. 



(b) The Cephalon. 



Excepting in Chiridotea, Harger, the cephalon is quadrate in outline. In 

 Idotea baltica (Pallas), /. neglecta, G. 0. Sars, and /. pelagica, Leach, it is cleft on 

 the posterior lateral margins, and in many species there is a more or less distinct 

 sinuous line towards the posterior margin. 



1. The Eyes. — Paired compound eyes are present in all the genera of the family. 

 In most species they are large, and situated dorsally or dorso-laterally. In a few 

 species they are quite small. In no genera or species of the family are they known 

 to be absent. 



2. Antennulm. — These are composed of a three-jointed peduncle with the flagellum 



