Chilton. — On Neiv Zealand Ifloteidae. 201 



Since ihis was written I have taken several specimens of 

 this species in rock-pools at Brighton, near Dunedin. The\ 

 were all taken on red seaweeds, and they closely resembled 

 the seaweed in colour, some of them also having a narrow 

 white streak of varying width down the middle of the back. 

 It is worthy of note that our three commonest species of 

 Tdotea are i;sually found on diflerently-colonred seaweeds 

 which they closely resemble in colour: Idotca uiujulata on 

 green, /. elongata on brown, and /. peronii on red. 



In his " Eevision of the Idoti'idre " Mievfi refers to tlie 

 resemblance between Idotea i)eronii, M.-Edw\, and /. siricta, 

 Dana, but does not unite them because of the uniarticulate 

 postabdomen of I. stricta. It appears, as I shall proceed to 

 show, that this character is subject to variation, and I have 

 therefore united the two species. The conclusion that they 

 both belong to the same species is to some extent confirmed by 

 the fact that, while I had labelled my specimens I. peronii, 

 those m Mr. Thomson's collection, which closely resemble 

 mine, had been labelled hy that gentleman as /. stricta. All 

 the New Zealand specimens that I have examined resemble 

 /. stricta. in having the postabdomen uniarticulate, but, unlike 

 that species, tliey have tliree sutures at the sides; the marks 

 from the first suture, indicating the coalescence of the segments, 

 can be traced further across the postabdomen than those 

 from the second and third sutures, and in some are very 

 faintly indicated almost right across, thus representing the 

 two segments as in I. peronii. Hence they may be consideicd 

 to be specimens of I. peronii in which the txco segments of the 

 postabdomen have more or less completely coalesced. I. stricta 

 is described and figured by Dana as having a uniarticulat(3 

 postabdomen, with only one suture on each side, so that the 

 difference of the number of sutures remains to be accounted 

 for : however, as M. -Ed wards has described one lateral suture 

 on the terminal segment of the postabdomen of the type- 

 specimen of his I. p)eroni.i, while, according to Miers, there are 

 really two present,''' it seemed very probable that the sutures 

 vary in distinctness, and that in the specimens examined by 

 Dana the second and third were so indistinct that they were 

 not observed by him; and this \"iew is fully confirmed by an 

 examination of specimens of I. caudacuta, Haswell, kindly foi- 

 warded to me by the Trustees of the Australian Museum, 

 Sydney. 



In the '-Zoology of the ' Alert,' "f Miers has already 

 suggested that /. caudacuta, Haswell, is probably identical 

 with I. peronii, M. -Edwards, and before noticing Mr. Miers's 



* "Jour. Linn. Soc. Zoology," xvi., p. 56. 

 + P. 311, footnote. 



