178 PROFESSOR CHARLES CHILTON ON THE 



or by a closely allied form in the southern is also shown to be increased, f.eaving out 

 of account the species known to be cosmopolitan, it has been long known that there 

 were some species identical in Arctic and Antarctic seas, though practically unknown in 

 the tropics ; nearly every writer on Antarctic Amphipoda has identified one or more 

 with northern species. It appears from examples like Orchomenopsis chilensis 

 (Heller), and others that might be quoted, that in these examples of " bi-polar " species 

 the species is not always entirely absent from the tropics, but exists there in deeper 

 waters, while it can live near the surface in the colder regions ; or that the tropical or 

 temperate form is so much smaller than the polar one that it has usually been 

 considered a separate species, and the existence of the species at intermediate localities 

 has been overlooked. It appears that, for some reasons not altogether understood, many 

 Amphipoda find their optimum environment near the Arctic and Antarctic regions, 

 and exist there in greatest abundance, attaining a size far greater than that usual for 

 similar forms in warmer seas. The ditficulty of deciding whether these smaller 

 forms are to be considered separate species or not is very great, and it must not be 

 expected in the present state of our knowledge that logically uniform results can be 

 arrived at. In some cases where the animal is abundant and specimens from many 

 localities have been examined, we may be able to group them into one large species, 

 while in other cases where only a few have been studied we are forced to leave them as 

 separate small species. Unfortunately, this leaves the groups distinguished by specific 

 names of very unequal value in the discussion of questions of distribution. 



11. List of Species. 



ANTARCTIC AND SUB-ANTARCTIC. 



Name of Species. Distribution and Remabks. 



1. Acontiostoma marionis Stebbing. Goughlsland, Marion Island, Straitsof Magellan, New Zealand. 



2. Amaryllis macrophfhalma Haswell. Australia, South Africa, South America, New Zealand, 



Indian Ocean. 



3. Cyphocaris anonyx Boeck. Widely distributed in both northern and southern seas. 



4. Lysianassa cubensis (Stebbing). South Africa and Gulf of Mexico. 



5. Alicella seotiae, sp. nov. South Atlantic ; an allied species found in the North Atlantic. 



6. Clieirimedon /emoraius (Pfeffer). South Orkneys, South Georgia, and Graham Land (Port 



Charcot). 



7. Tryphosa murrayi Walker. Off Coats Land and South Victoria Land. 



8. Tryplwsites stehhiniji (Walker). Off Coats Land and South Victoria Land. 



9. Orchoinenella pinguides Walker. South Orkneys and South Victoria Land. 



10. Orchomenella macronyx Chevreux. South Orkneys and Graham Land (Port Charcot). 



11. Waldeckia zschauii (Pfeffer). Off Coats Land, Graham Land, and South Victoria Land. 



12. Orchomenopsis nodimanus Walker. South Orkneys and South Victoria Land. 



13. Orchomenopsis chilensis (Heller). In all seas, northern and southern. 



14. Orchomenopsis (?) noatsi, sp. nov. 0£E Coats Land. 



15. Harpinia vbiusifrons Stebbing. Widely distributed in Antarctic and sub-Antarctic seas. 



16. Leucothoe spinicarpa (Abildgaard). In all seas. 



17. Amphilochus squamosus G. M. Thomson. South Orkneys, Marion Island, and New Zealand. Perhaps 



identical with A. neapuUtanus of northern seas. 



(rot. soc. edin. trans., vol. xlviii., 460.) 



