202 Transactions. — Zoology. 



suggestion I had come to the same conchision from a com- 

 parison of the descriptions of the two species. In his " Eevi- 

 sion of the Austrahan Isopoda,"'^'- Mr. Haswell, adopting 

 Miers's suggestion, omitted I. caudacuta from the hst without 

 connnent. I have now been able to examine specimens of 

 /. caudacuta, Hasw., from Warrnambool, Victoria, and to 

 compare them with my New Zealand specimens of I. 'pcronii, 

 M.-Edw. The result fully proves the truth of Mr. Miers's 

 suggestion, while, as I have already hinted, the specimens 

 present certain features wdiich still further connect I. peronii 

 and I. stricta. In the specimens from Warrnambool the body 

 is rather more convex and somewhat narrower than in my New 

 Zealand specimen of I. peronii, especially in the postabdomen, 

 and the lateral margins are rounded instead of thinning out,, 

 and form a more or less distinct edge. The postabdomen 

 consists of two segments, but, although the division-line is 

 traceable right across with a little difficulty, the two segments 

 are firmly anchylosed together, and the two sutures on the 

 second segment are very indistinct, the first one especially 

 so. The facts already stated show that there is consider- 

 able variation in the distinctness of the division-marks on the 

 postabdomen, and there is therefore no difficulty whatever 

 ill seeing that Dana's description of I. stricta, as possessing 

 a uniarticulate postabdomen with a single suture on each 

 side, was taken from a specimen in which the division-marks 

 were a little more indistinct than in the Warrnambool speci- 

 mens. It is perhaps worthy of note that, while in these 

 specimens the postabdomen is composed of two segments, and 

 the following two pairs of sutures are very indistinct, in the 

 New Zealand specimens there is only one segment to the 

 postabdomen, but all three sutures are clearly marked. 



One of the specimens from Warrnambool is a female bearing 

 eggs in the brood-pouch, and this specimen has the thorax 

 somewhat expanded, though not to anything like the same 

 i^xiexit 'A?, in Idotea elongata ; the length is 22-5mm., and the 

 greatest breadth is about 6-5mm. One of the specimens in 

 Mr. Thomson's collection, again, is a female bearing eggs, and 

 in this specimen also there is a slight w'idening of the thorax ; 

 tbe length is 25min. and the greatest breadth T'Smm. In 

 specimens not bearing eggs the proportionate breadth is 

 slightly less than this : thus, one specimen has — length 

 27- 5mm., breadth 7- 5mm. ; another, length 22- 5mm., breadth 

 6mni. ; a third, length 16mm., breadth 4mm. 



The specimen in Mr. Thomson's collection from Moeraki is 

 a young one, only 5mm. long. The front margin of the head 

 is not emarginate, being even very slightly convex in the 



* " Proc. Linn. Soc. N.S.W.," vol. ix., part 4. 



