A. H. Clark — Study of Recent Crinoids. 



65 





Total 

 Range 



Average 

 Eange 



Mean 

 Depth of 

 Habitat 



Total 



Thermal 



Eange 



Mean 



Thermal 



Eange 



Mean 

 Tempera- 

 ture of 

 Habitat 



Eecent Species 

 belonging to 

 fossil Genera 



1295 



425 



327 



38°'8 



ll°-0 



53°'4 



Plus 



Democrinus 



1295 



519 



366 















Exclusively 

 Indo-Pacific 

 Genera 



2575 



244 



264 















Exclusively 

 Atlantic 

 Genera 



1300 



401 



291 















Genera com- 

 mon to both 

 Oceans 



2900 



1057 



785 















According to their geographical distribution these genera 

 group themselves as follows : 



Confined to the western Pacific : 



Eudiocrinus 



Catoptometra (Fossil in Patagonia) 



Proisocrinus 



Carpenter -ocrinus 



Confined to the western or western and northern Atlantic, 

 hut occurring as fossils in the Indo-Pacific basin : 



Isocrinus 



Hhizocrinus 



Holopus 



Common to the Indo-Pacific and Atlantic : 

 Democrinus 



It is interesting to note that all but one of these genera is 

 chiefly developed in shallow water ; this single exception is 

 also the only one which, so far as we know, does not occur 

 within 100 fathoms of the snrface, three of the others being 

 entirely confined to water of less than 155 fathoms in depth. 



In the total range, average range, and mean depth of habitat 

 these genera show a close approximation to the genera peculiar 

 to the Atlantic, in contrast to those peculiar to the Indo-Pacific, 



Am. Jour. Sci. — Fourth Series, Vol. XL, No. 235. — July, 1915. 

 5 



