GEOGEAPHICAL AND BATHYMETRICAL DISTPJBUTION. 



We do not yet possess the data necessary for a complete exposition of the geographi- 

 cal distrilnition of the Plumularidas. It may be generally asserted of this group that it 

 attains its greatest development in the warmer seas of both hemispheres, and that in 

 tropical and sub-tropical regions it has its maximum in multiplicity of form, in the size 

 of the colonies, and in individual profusion. 



The dredgings of the Challenger and of the United States Exploration of the Gulf 

 Stream would further seem to point to two centres of maximum development within the 

 area thus indicated, — an eastern centre, which is situated in the warm seas around the 

 Philippines and other islands of the East Indian Archipelago, and a western centre, 

 which will be found in those which lie around the West Indian Islands, and bathe the 

 eastern shores of Central and Equinoctial America. From these two centres the laro-est 

 known Plumularian colonies have been obtained, and we learn, on the authority of 

 Semper, that the natives of the Philippine Islands regard with dread, in consequence of 

 their formidable stinging powei'S, some of the great Plumularians which occur around 

 their shores. 



These eastern and western centres of Plumularian distribution remind us of the two 

 great centres in which the Cheiroptera have their maximum development, as seen in the 

 gigantic bats of both hemispheres, — centres of Cheiropteran distribution which are nearly 

 coincident with these regions of maximum development in the PlumiUaridge. 



In bathymetrical distribution the Plumularidse present considerable variation. 

 Among the species described in the present Report some are quite littoral, having been 

 dredged from depths ranging between 8 and 20 fathoms. The greater number however 

 of the Challenger species have been obtained from dep)ths between 20 and 150 fathoms, 

 while the dredge has brought up three species, Aglaophenia fiUcula, Acjlaophenia acacia, 

 and Pohjplumaria pumila, from a depth of 450 fathoms. The striking and beautiful 

 genus Cladocarpus consists of eminently deep water forms, and of the two species here 

 described one, Cladocarpus formosus, was obtained in the Japan Seas from a depth 

 varying between 420 and 775 fathoms — the same species having been dredged by the 

 " Porcupine " in the seas lying to the north of Scotland from 167, 560, and 632 fathoms 

 — while Cladocarpus pectiniferus was dredged by the Challenger off the Azores from 900 

 fathoms. This last is the greatest depth from which any Plumularidan is known to have 

 been obtained. 



