390 



THE VOYAGE OF H.M.S. CHALLENGER. 



B. 



C. 



Summary. 



I. 9 species found at depths down to 100 fathoms. 



11. 11 (or 12) species found between 100 and 250 fathoms. 



III. 13 (or 12) species found between 250 and 500 fathoms. 



IV. 7 species found between 500 and 700 fathoms. 

 V. 4 species found between 700 and 1200 fathoms. 



VI. 8 sjiecies found between- 1200 and 2000 fathoms. 



VII. 2 species found between 2000 and 2500 fathoms. 



1 species descending from Table 



I 

 2 

 2 

 2 

 1 

 1 

 1 



9 species found at depths down to 100 fiithoms. 

 14 (or 15) „ „ 250 



22 „ „ 500 



To these we may fairly add the two species of Metacrinus found near Singapore by 

 one of the ships of the Eastern Telegraph Company, as it is improbable that they were 

 living at a greater depth than 500 fathoms. 



It has been the custom of late years, more especially since the discovery of Penta- 

 crinus wyville-thomsoni and Bathycrinus gracilis by the "Porcupine," at 1095 and 2435 

 fathoms respectively, to regard the Stalked Crinoids as pre-eminently abyssal types, and 

 as probably forming " rather an important element in the abyssal fauna." ^ It will be 

 apparent, however, from the statistics given above, that subsequent researches have not 

 altogether confirmed these views. If, as Mr. Agassiz has done in his Eeport on the 

 Echinoidea,^ we take the limit of the continental line at 500 fathoms, it appears from 

 Summary C, that twenty -four of the thirty- two recent species of Stalked Crinoic's, or 

 75 per cent., occur within this limit ; while nine of these, living at depths less than 100 

 fathoms, may be called littoral. 



Although numerous and extensive dredgings have been carried on in the abyssal zone 

 {i.e., at depths below 500 fathoms) during the last fifteen years, Stalked Crinoids have 



' The Depths of the Sea, p. 455. - Zool. Chalh Exp., part ix. p. 222. 



