253 GEOGRAPHICAL AND GEOLOGICAL DISTKIBCTION. 



occurs in the Cretaceous deposits, and Corallium, to which the 

 red coral of commerce belongs, already in the Jurassic. The 

 distribution of the latter genus appears to be at the present time 

 confined principally to the Mediterranean Sea, -where it ranges in 

 depth from shallow water (twenty-five to fifty feet) to water over 

 one thousand feet, and to the Atlantic off the northwest of Africa. 

 A species of the genus (Corallium stylasteroides) has been obtained 

 off the coast of Mauritius, and another from Japan (C. [Pleuro- 

 corallium] secundum). The officers of the "Challenger" expedi- 

 tion obtained water-worn fragments at Banda and the Ki Islands, 

 indicating the existence of the genus in the Malay Archipelago. 



BKACHIOPODA. 



The most detailed information that we possess respecting the 

 geographical and bathymetrical distribution of the recent Brachio- 

 poda is furnished by Davidson in his report appended to the nar- 

 rative of the "Challenger" expedition (1880). Of the one hundred 

 and thirty-five species and varieties (referable to some twenty genera 

 and sub-genera) here recognised, whose distribution covers all parts 

 of the oceanic surface, from Spitzbergen (Terebratella Spitzbergensis, 

 Terebratulina caput-serpentis) and Franklin Pierce Bay (latitude 

 79° 35' ; Rhynchonella pisittacea) on the north to Kerguelen Island 

 and the Straits of Magellan on the south, there are few, if any, 

 that can in any way be considered truly cosmopolitan, although 

 species of broad distribution are not exactly uncommon. Tere- 

 bratulina caput-serpentis is perhaps the most widely distributed of 

 all the known forms, its habitat comprising the Arctic seas of both 

 the Eastern and Western Hemisphere (Spitzbergen, Davis Strait), 

 the Atlantic coast of Europe as far south as Spain, Jamaica, Corea, 

 and Australia. Terebratula Wyvillii is found off the coasts of South 

 Australia, the Falkland Islands, and Chili. As a rule it may be 

 said that the north and south extension of a species is greater 

 than the east and west extension, a condition doubtless due in 

 principal part to the general disposition of the land areas in this 

 direction. Arctic or circumpolar species have naturally a broad 

 lateral dispersion. Species restricted in their habitat to shallow 

 water are as a rule much more sharply circumscribed in their range 

 than those inhabiting the greater depths, as might reasonably have 

 been supposed. Localisation to limited coast lines, as Japan, 



