CRUSTACEA MALACOSTRACA. II. 





B. Geographical and bathymetrical Distribution. 



The fact that the "Ingolf" alone raised the number of species of Tanaidacea inhabiting the 

 area explored from 9 to 72, thus to almost half the number of species known from the entire world, 

 proves with absolute certainty that our knowledge of this order is still in its infancy. But an exami- 

 nation of the list of localities for each species affords further interesting results. 



The major part of the 149 species previously known were taken exclusively or generally in 

 depths from o to 50 or 60 fathoms, several species generally in depths from 50 to 200 or at most 300 

 fathoms, and scarcely twenty species — secured mainly by the '■Porcupine", the ''Valorous", the "Challenger" 

 and "l'Hirondelle" — had been found generally or exclusively in depths more than 300 fathoms, some- 

 times in more than 1000 fathoms, and the greatest depth recorded is 2050 fathoms. But among the 

 52 new species established in this report about 44 were taken either most frequently or — and in 

 most cases — exclusively in depths exceeding 300 fathoms and often in depths between 700 and 

 1870 fathoms. Some species formerly taken in lesser depths were now found to be not uncommon in 

 considerable depths. Thus, the "Ingolf" discovered more than twice as many deep-sea species as 

 hitherto recorded from all seas together, and the great majority among them are small, less than 

 3.5 mm. and generally 1.6—3 uim. long. 



Another point of great interest is that the richest harvest was yielded by some of 

 the deepest stations in the warm area South and West of southern Greenland. At 

 Stat. 78 (South-West of Iceland) an enormous quantity of bottom material was hauled up from 799 

 fathoms and 9 species of Tanaidacea were found; at Stat. 32 (Davis Strait) the quantity of bottom 

 material from 318 fathoms was very large and rendered 8 species. But at St. 38 (entrance of the 

 Davis Strait) the bottom material procured from 1870 fathoms filled in sifted condition scarcely more 

 than a good tea-cup, and in that I found even 9 species. And two of the stations West of South 

 Greenland were still richer; the sifted material from Stat. 36, 1435 fathoms, was about a liter and 

 contained 11 species, while from Stat. 24, 1199 fathoms, I have 12 species of Tanaidacea. The last- 

 named station thus rendered 4 species more than the whole Norwegian North-Atlantic Expedition, about 

 half as many species as hitherto known from the Mediterranean; the harvest from the four deep-sea 

 localities Stat. 22, 24. 36 and 38 is in all 30 species, while Sars in his standard work from 1896—97 

 has only 28 species from Norway. 



From all these statements we may safely draw the conclusion, that the deep sea with 1100 to 

 1870 fathoms in the warm area in the North Atlantic has a much richer fauna of Tanaidacea than 

 any large northern or tropical part of the Atlantic along the coasts and with depths irom o to 

 100 fathoms. And as it seems very improbable that the deep sea near South Greenland is propor- 

 tionately richer than the deep sea of the subtropical or tropical Atlantic, the Indian Ocean or the 

 Pacific, we may infer that hundreds of unknown species of Tanaidacea inhabit the deep areas of the 

 Oceans, and that the fauna from about 300 and down to at least 2000 fathoms is much richer than 

 the fauna living in depths between o and 300 fathoms. 



In the list of the "Ingolf" stations we find thirty places with the temperature at the bottom 

 below zero; these stations belong to the cold deep-sea area and their depth ranges from about 300 to 

 1300 fathoms. Of our Tanaidacea 8 species are exclusively from these stations. The warm deep-sea 



