DEAD SEA-LILIES. 73 



The star-fish and sea-urchin are the most familiar 

 examples of echinoderms. Indeed, the sea-lily may 

 be called a stalked star-fish. There are two types 

 of Crinoids. (1) Sessile, which, after the develop- 

 mental stages have been gone through, are not 

 permanently fixed or " rooted," and hence are spoken 

 of frequently as "free." A common living example 

 of these is Comatula rosacea. (2) Stalked or 

 pedunculated, which are permanently fixed when 

 fully developed. Apiocrinus rotundus is a good 

 example (Frontispiece). The column is often very 

 long, and is composed of many joints, which are so 

 articulated with each other as to give great flexibility 

 to the stem. 



A Crinoid may be described as an echinoderm 

 having its body fixed, during a part or the whole of 

 its existence, by means of a flexible stalk or column. 

 The body is cup-shaped, and hence is called the 

 " Calyx." It is covered with an external armour 

 of calcareous plates, the upper surface being 

 protected with smaller plates, loosely connected 

 together by a leathery membrane. Its mouth is on 

 the upper surface, thus differing from the star-fish, 

 which has the mouth underneath. From the margin 

 of the body spring five jointed arms, which some- 

 times subdivide, thus producing ten, or even fifteen, 

 branches. These carry innumerable pinnules, and 

 so form a cluster of delicate feathery plumes. 



In regard to the mode of locomotion of larval 

 and free Crinoids, the ambulacral, or water vascular 

 system, respiration, and the nervous and reproductive 

 organs, I must refer the reader to the text-books, 



