EUEOPEAK FORMS OF THE CIROLA.]SriJr^, . 339 



exhibiting excelient specific characters, are closely allied and so 

 similar in general aspect, size, and colour, that authors have 

 certainly often committed mistakes in naming their material ; 

 for this reason I think that at least some of the statements 

 in the literature on the occurrence of the species, especially 

 JE. piolchra, are erroneous and misleading. Furthermore, the 

 discovery of a new and large species of Girolana in abundance 

 on the northern coast of France, and closely allied to G. horealis, 

 proves that great caution is necessary in determining species of 

 this group. In the following account I shall endeavour to 

 distinguish as well as possible between trustworthy and doubtful 

 statements as to localities, but where no description or figures 

 are given it is, of course, only a kind of calculation of proba- 

 bilities, and even a gross error may readily escape discovery. 



Conspectus of the Genera *. 

 A. Peduncle of antennfe with at least five very distinct, 

 movable joints t- Lobe from second joint of the 

 maxillipeds furnished with one hook or two or three 

 hooks. Peduncle of uropods produced considerably or 

 much backwards, so that the articulation between 

 peduncle and endopod is rather long. 



a. First and second pairs of pleopoda subsimilar, with 



the endopod submembranaceous ; peduncle of first 



pair much broader than long I. Cirozana, Leach, 



b. First pair of pleopoda very firmly chitinized every- 



where, constituting a large operculum, with the 

 peduncle longer than broad and the inner branch 

 elongate ; second pair of pleopoda with both rami 

 submembranaceous and the peduncle broader than 

 long II. CoNiLERA, Leach. 



* This key is in the main only a translation of the Latin conspectus in my 

 monograph. 



t In 1890 I described and figured five joints in the peduncle of the antennas 

 in Cirolana. In the paper, " Tlie Deep-sea Isopod AmirojMS branchiatus, Bedd., 

 and some Remarks on Bathynomus gigantcus, A. M.-Edw." (Journ. Linn. Soc, 

 Zool. vol. xxix. pp. 12-25, 1903), 1 showed that this peduncle in Bathynomus 

 gigcmteus consists of six movable joints. Having found the basal joint hitherto 

 overlooked in this animal, I was able to point out the same joint in Cirolana 

 horealis and C. Cranchii : the joint is distinct, situated at the outer margin of 

 the joint hitherto considered as the first, but it is not easy to catch sight 

 of; it is probably found in all species of Cirolatia, and I have besides observed 

 it in Conilera. The mode of expression in the conspectus is chosen for 

 practical reasons. 



23* 



