346 



most of the species of this genus live in shallow water, 

 A. loveni Beel occurring in three to four fathoms. This 

 genus is perhaps the most cosmopolitan of modern crinoids, 

 its geographic range being between eighty degrees northern 

 and fifty-two degrees southern latitude. The following- 

 modern stalked crinoids have been obtained in less -than 

 ninetv fathoms of water : * 



Eudiocrinus indivisus Semp., 30 fathoms. 

 Metacrinus rotundus Car])., TO fathoms. 

 Pentacrinus asterius L., 80 fathoms. 

 P. decorus Wy. Th.. 84 fathoms. 

 P. n i i) lleri Oerst, 84 fathoms. 

 Promachocrinus kerguelensis Carp., 28 fathoms. 

 Rhizocrinus lofotensis Sars, 80 fathoms. 

 R. rawsoni Pourt., 73 fathoms. 



The egg of Antedon develops into an egg-shaped mero- 

 planktonic larva, which has a tuft of long flagella on the 

 anterior end, and five ciliated rings surrounding it, No 

 month or anus is present. The embryo swims about for a 

 length of time, varying from a few hours to several days, 

 and, on settling down to a benthonic life, attaches itself at a 

 point on the ventral side between the first and second ciliated 

 rings. The whole anterior part, as far as the third ciliated 

 ring, becomes the stalk, the posterior part developing into 

 the calvx. In Antedon the stem is retained only during the 

 earlier stages of development, the adult animal being free. 



Asteroidea, Ophiuroidea — These belong to the marine 

 vagrant benthos, living mainly in shallow water or in mod- 

 crate depths, though some species descend to depths of 2.000 

 fathoms or over. Some littoral starfish can undergo an 

 exposure for several hours in regions laid bare by the tide. 

 A sandy or muddy bottom seems to be the most character- 

 istic facies for these animals, and from such bottoms 

 thousands are often brought up in a single haul of the 

 dredge. Their relative scarcity in beds in which they are 



* From list given by Walther in '94, pp. 298—300. 



