18 



BRANCH ECHINODEKMATA. 



BRANCH ECHINODERMATA (Sk i no dsrm-a ta>. 



THE STAR-FISHES, ETC. 



The ECHINODERMS (e kin' 6 dermz) present a radial 

 structure, have the digestive tract without direct con- 

 nection with the body cavity, have the skin indurated 

 (in'du rat ed) by calcareous plates, and are generally free 

 to move about. All are marine. 



CLASS CBINOIDEA (krlnoid'ea). 



At early periods of the earth's history, the CRINOIDS 

 (kri'noidz) abounded ; now they are extremely rare, being 

 seldom obtained except from deep water by dredging. 



FIG. 28. 



ORDER BRACHIATA (bra ki a'ta). 



The Norwegian Crinoid found in the 

 North Atlantic at depths of 100 to 1,000 



fathoms, is one of the smaller species. 







A long stem attached to the mud by 

 root-like branches, supports a five-rayed 

 animal, of the general appearance of a 

 lily. As in the other metazoan animals 

 thus far treated, the mouth is placed in 

 the center of the disk from which the 

 main rays diverge ; but, unlike the Cce- 

 lenterates, a limy deposit prevents the 

 quick contraction of any portion of the 

 animal, and renders movement slow and 

 limited. The food, moreover, which has 

 been thrust down the oesophagus, has the 

 nutritive portions absorbed by the walls 

 of an alimentary canal. Along the upper surface of each 



Rhlzocri'nus loften'sis. 



The Norwegian Crinoid, 



or Stone-lily. 



