470 CRINOIDEA ; COMATULA ; PENTACRINUS. 



rocks and other solid submarine bodies. The mouth is then di- 

 rected upwards, and the long, branched arms are waved about 

 in various directions in search of food, presenting a very elegant 

 appearance. 



1109. In its young state the Comatula is fixed to submarine 

 objects, being attached with the mouth upwards to the upper 

 extremity of a long flexible stalk composed of calcareous cylin- 

 ders. In this form it closely resembles a great group of 

 Echinoderms, which were formerly excessively abundant, as 

 their remains sometimes constitute nearly the whole mass of 

 thick strata of rock, and which were attached by a similar 

 flexible calcareous stem during their whole existence. The 

 young Comatula^ in the attached state, was indeed formerly re- 

 garded as a member of this group, and described as such under 

 the name of Pentacrinus europceus, but it is now known that at 

 a certain period of growth the disc and arms quit the stem, and 

 pass the remaining term of their existence in a state of freedom. 

 The only living representatives of the Encrinidce, or true Sea-lilies, 

 are inhabitants of the West Indian seas, where a few specimens 

 of two or three species have been found at great depths. One 

 of these, the Pentacrinus caput Medusce, is of considerable size, 

 and it is to its discovery that we are indebted for the greater 

 part of our knowledge of the anatomical structure of this re- 

 markable group of animals, most of whose representatives have 

 so long since passed away. In this creature the disk and arms 

 are formed like those of the Comatula ; the latter are thickly set 

 with jointed lateral appendages of considerable length. The 

 stem is more than a foot long, and composed of a large number 

 of pieces similar to those of the arms. From this stem there 

 arise, at regular intervals, several verticils, or .whorls, of second- 

 ary arms ; which do not subdivide, and are destitute of lateral 

 appendages. All these parts are covered with a fleshy integu- 

 ment, by which they are produced, and to which they owe their 

 power of movement. This integument seems to dip down be- 

 tween each joint, and to form the connecting medium between 

 the different pieces. As the base of the stem of the recent species 



