338 DISCOVERY REPORTS 



vascular system of the Discovery material of Atolla differs in some respects (very large 

 amount of pigmentation, length of the lappet canals) from the descriptions given hitherto . 

 In accordance with the results of Broch an increase of pigmentation should be found 

 with increase in depth. A. bairdi and verrilli are typical of the North Atlantic region 

 and do not occur south of 55° S. ^. wyvillei has its most northern limit in the Gulf of 

 Guinea and occurs only in a layer of water of low salinity (34-5-3475 7oo)- It is the 

 only form in Antarctic waters or in waters of Antarctic origin. 



Very probably wyvillei on the one hand, and bairdi and verrilli on the other hand, 

 are distinct geographical forms confined to special currents or regions. A. zvyvillei 

 (typical form) sinks slowly into deeper layers proceeding from the Antarctic to the Cape. 



The rich material of A. chiini (43 specimens), in different stages of development, 

 made it possible to complete the short description of this "rare" medusa given by 

 VanhoefTen,with respect to the gastro-vascular system, subumbrellar papillae, pigmenta- 

 tion and warts on the lappets. The distribution of this form is exclusively restricted to 

 the sub-Antarctic part of the Atlantic ; the species has not been found in Antarctic 

 water south of the latitude of Cape Horn, nor north of 30° S. Most individuals have 

 been caught in the neighbourhood of continents or groups of islands. A. chuni belongs 

 to the "intermediate fauna" of Bigelow, and prefers deeper layers than wyvillei with 

 a maximum occurrence in about 1 200-1 300 m. No specimen has been caught between 

 the surface and 900 m. depth. With regard to salinity the occurrence of ^. chmiiis con- 

 fined to strata of 34"35-3475 7oo- 



Pelagia tiocfihica. A catch of eight specimens at St. 168 in the waters between the 

 South Orkneys and Clarence Island, in 60° 58' S, is very interesting, for Vanhoeffen 

 points out in the Valdivia Report (1903, p. 37) that 42° S is the southern limit of 

 geographical distribution of this medusa. It is the first time that a Pelagia has been 

 found in these cold Antarctic waters. 



I believe Desmonema gaiidichandi , Lesson, and Desmonema chierchiana, Vanhoeffen, 

 to be two different species. 



Phacellophora ornata (Verrill). A young developmental stage of this large medusa has 

 been found in Elephant Bay, West Africa, an important locality since this form has 

 hitherto been found exclusively at Eastport, Maine, in Fundy Bay, and only once in 

 the South Atlantic near the coast of Montevideo. 



In the first place I wish to thank my wife, Dr G. Stiasny-Wijnhoff, for her in- 

 valuable assistance in many difficult cases, her indefatigable patience and the oppor- 

 tunity to discuss with her the interesting problems relating to the development and 

 distribution of the deep-sea medusae. 



The manuscript has profited very much from a revision of the text kindly under- 

 taken by Dr Stanley Kemp and Dr N. A. Mackintosh; moreover I am obliged to 

 Dr Kemp for much valuable information and advice. The Discovery results on 

 hydrography were not published when this report was written and I am indebted to 

 Mr G. E. R. Deacon of the hydrographical staff of the expedition for suggestions and 



