78 



Stebbing to receive the deep-water species Anceus gigas (Bed- 

 dard) ; the chief differences between Paragnathia and Gnathia lie 

 in the 5-jointed gnathopods found in both sexes of the former and 

 in the absence of maxillipeds in the female. I have found this very 

 interesting Crustacean exceedingly plentiful in the banks of 

 Christchurch Harbour throughout the summer and autumn, but 

 I am inclined to think that the females die after releasing the 

 larvae from their body-cavities, and that many of the males are 

 killed off during the winter. 



The only other brackish-water Isopod of any interest which 

 occurs in this district is Idotea viridis (Stabber), a species which 

 is very plentiful in the lake in Poole Park. It is by no means a 

 common animal in most parts of the country, and is noteworthy on 

 account of its singularly beautiful and protective colouration. It 

 lives among the delicate green Algae which are so plentiful in 

 the lake, and by its pure green colour and extraordinary trans- 

 parency renders itself almost invisible, and it is by no means an 

 unusual thing to pass over several of these pretty little creatures 

 when actually searching a piece of weed for them. The male and 

 female are, for some inexplicable reason, of quite different shades 

 of green and are also distinguished by the general form of the 

 body to an extent not usually found among the members of this 

 family. A very good description of this species is given by 

 Prof. Sars in his " Crustacea of Norway," in which book there 

 are also fine illustrations of both sexes. 



Numerous other species of Idoteidce are found in this district, 

 but none of them is of any particular interest. Zenobiana 

 prismatica is a rather scarce spec : es found in Studland Bay and at 

 Totland, the genus being distinguished from Idotea by an 

 additional free segment in the abdomen. Idotea linearis, a some- 

 what common species which I have taken crawling up the ropes 

 attached to lobster-pots around Freshwater Bay, frequently 

 reaches inches (31 mm.) in length excluding the antennae, 

 which are themselves often quite an inch (25 mm.) long. Mr. 

 W. E. Collinge, of St. Andrew's University, who has just written 

 a very full revision of the British Idoteidae, tells me that he 

 believes there is an undescribed species of Synisoma, one of the 

 genera of the Idoteidae tc be found along this coast. Closely 

 related to these Isopods and belonging to the same sub-order — 

 the Valvifera — is Astacilla, the " little lobster," which occurs in 

 Totland Bay. This weird-looking little creature lives among 

 coralines, and is peculiar for its prehensile antennae to which its 

 whole brood of young ones cling, and strange indeed it looks, 

 sitting bolt upright on its hinds legs, as is its custom, with a 

 dozen babies hanging on to its unusual head-gear. 



On the rocks perhaps the most noticeable Isopods are the 

 various members of the family Sphaeromidae — Sphaeroma, Dyna- 

 mene, and Cymodoce — which have the power of rolling themselves 

 into balls after the manner of certain well-known woodlice. When 

 in th : s condition they are often very difficult to secure, as they will 



