70 DR. W. E. COLLINGE ON THE 



of five distinct segments and a palp on the maxillipedes having five joints. 

 Such a type is probably represented by Proidotea, Racovitza and Sev., 

 although the maxillipedes have not been seen of this extinct genus. Mesidotea, 

 Eichardson, would follow, and then C/dridotea, Harger, where a segment 

 o£ the metasome has become fused, but a suture remains indicating it. 

 Although undoubtedly related to the former genus, the palp of the maxillipede 

 is composed of only three joints. The position of Macr.ochiridoth.ea, (Jhlin, 

 and Chiriscus, Richardson, is somewhat doubtful. 



In a second group we have Pentidotea, Zenobiana, Glyptidotea, Paridolea, 

 Pentias, Crabyzos, Cleantiella, and Engidotea, in all of which genera the 

 palp of the maxillipede possesses five joints. In Zenobiana there is often a 

 metasome composed of five segments, and in all the remaining genera there 

 are indications of four segments. 



In a third group must be placed Idotea, Colidotea, Eusymrnerus, Erich- 

 sonella, Synisoma, and Euidotea, all with a four-jointed palp of the maxilli- 

 pede and one to four metasomatic segments. 



Finally, in a fourth group we have Edotia and Synidotea, each with a 

 three-jointed palp of the maxillipede and a single metasomatic segment and 

 one suture. The Table on p. 71 summarizes these and other structural 

 features. 



Whilst there is fairly conclusive evidence to show that the genera of the 

 first group are closely related to one another (cf. 19 & 10), I do not think 

 that it is possible, in the present state of our knowledge, to state that a 

 similar relationship is evident between the genera of the remaining groups. 



As I have elsewhere pointed out (12 ft), the classification of this interesting- 

 family of Isopoda is as yet very uncertain. The known genera and species 

 in all probability constitute only a very small part, of those actually existing. 



The distribution of the members of this family, which contains some two 

 dozen genera, including about one hundred and twenty-five species, as at 

 present known, is curious. Miers (16) and the earlier writers all regarded 

 them as having a wide distribution in all parts of the world, but being more 

 abundant in temperate and colder seas than in the tropics. At that time the 

 majority of species had been obtained in Northern latitudes, but of recent 

 years many new species have been obtained from the Mid and Southern 

 Pacific, Indian Ocean, and Antarctic. Thus, Ohlin (18) has described two 

 new species of Macrochiridotliea and two of Edotia, and a new species of 

 Erichsonella from South America; Chilton (5), the curious Idotea /estiva 

 from New Zealand ; Miss Richardson *, a new species of Glyptonotus from 

 the Antarctic ; Barnard (1,2), three new species of Paridotea and one of 

 Synidotea from South Africa. More recently! I have described a new 



* Bull. Mus. Paris, 1900, p. 187. 



t Rec. Indian Mus. vol. xiii. (1017) pt. 1, p. 1, pi. i. 



