NO. 1350. NATURAL HISTORY OF THE ISOPODA— RICHARDSON. 27 



niscus cavernicola Budde-Lund from grottos in the Pyrenees; Asellus 

 caimticKH Schia'dte from suhtorriineau waters in Central Enrope; Trlclio- 

 niscus stygius Ncmec from a Gabroviza j^rotto near Trieste (pro})ably 

 identical with Typhloniscus stygkis Joseph, according to Nemec, who, 

 howf^'er, considers the species a true Trlchoufxcus)^ and StotdKellns 

 vJrc! Dollfus from subterranean waters (wells) near Cevcnnes, at a 

 depth of 150 meters. 



10. BATHYMETRICAL DISTRIBUTION. 



Man}^ of the marine forms are found floating on algaB or swimming 

 freely near the surface of the water. Below the surface they have 

 been taken from depths ranging from 1 to 2,040 fathoms. Among 

 the deep-sea forms, the species Apseudes gracilis Norman and Steb- 

 bing may be mentioned; it comes from a depth of 1,450 to 1,785 fath- 

 oms, and is confined to the deep waters of the North Atlantic. The 

 families which are known to descend below 1,000 fathoms in the North 

 Atlantic are — " 



ApseudidfB Genera Apseudea, Sphyrapus. 



Tanaidfe Many genera. 



Anthuridae Many genera. 



Gnathiidffi Genus Gnathia {Anceus). 



Cirolanidfe Genus Cirolana. 



Idoteitlio Genus Chiridotea. 



Asellid;e Genus Nannonii^cus. 



Arcturid;e '. Genus Astacilla. 



Munnidfe Genera Ischnosoma, Macrosti/lis. 



Munnopsidpe Genera Munnopsis, Ilyaraelina, and Eurycnpe. 



In the Southern Sea the Serolidse have been found distributed over 

 a wide area in very deep waters, descending to 2,040 fathoms. 



yEga maxima Hansen, from (yocos Island, comes from a depth of 

 1,175 fathoms; Astacilla cxca Benedict, from oft' Maryland, was taken 

 at a depth of 1,825 fathoms, and Pseudione Udjerculata Richardson, 

 from Port Ortway, Patagonia, comes from a depth of 1,050 fathoms. 



One of the characteristic features of the deep-sea forms, or '"Bas- 

 salian animals," is their distribution over wide areas. 



11. GEOGRAPHICAL DISTRIBUTION. 



The influence of temperature has been considered of paramount 

 importance in the distribution of life in the seas. 



According to Prof. James D. Dana, the preponderance of species is 

 in the Temperate Zone, or Pararctalian and Notalian Realms.^ Species 

 outside of the Tropical Zone or Tropicalian Realm'' are of the highest 

 rank: and usually the largest of the order, the giant forms, such as 



« For above list refer to Stebbing, Trans. Zool. Soc. London, XII, Pt. 4, 1886, p. 1. 



''Tlu' above nomenclature was suggested l)y Dr. Theodore Gill for the primary 

 iiuirine regions or realms in place of the zones used by Dana. IVoc. liiol. Soc. 

 Washington, II, 1885, jtp. \-m. 



