26 University Geological Survey of Kansas. 



ORINOIDEA. 



Crinoids are those animals known as sea-lilies or stone- 

 lilies. They live in the sea at varying depths, from shallow 

 water to 3000 fathoms. They were very abundant during geo- 

 logical time, and probably reached their maximum development 

 during the Carboniferous period. They are not well adapted 

 for preservation as fossils. Their skeletons are made up of 

 angular pieces fitted together, but which usually fall apart 

 when the animals decay, so that the preservation of an entire 

 individual is a comparatively rare occurrence. It is not uncom- 

 mon to find masses of stone almost entirely made up of these 

 pieces, since the animals were gregarious, living in colonies as 

 they do at present. During the Carboniferous and Triassic 

 periods they were much more abundant than now. 



Most of the crinoids are attached to the mud by stems which 

 have rootlets at the base to anchor them. However, some of the 

 forms are free during most, or all, of their lives. These stems 

 had small canals running through their centers. They were 

 either round or three- to five-sided. They are often found 

 weathered out in the forms of little discs, which are generally 

 called " Indian beads." Upon the upper end of this stem rests 

 the calyx or cup-shaped base of the animal. The calyx is 

 generally composed of three circlets of plates. First, the in- 

 frabasals, or the plates which rest on the top of the stem. 

 There are usually five of them, and they are quite small, and 

 occasionally are united into one, or they may be entirely want- 

 ing. Above these are the basals, or second ring of plates, which 

 are longer and generally six-sided. Upon these rest the third 

 row, or the radials, which support the arms and the top part 

 of the animal. There are usually five of the radials, which 

 are flat on top and five-sided. On the posterior side of the ani- 

 mal there is often a series of plates supporting the ventral tube, 

 above which the anal opening is situated. These plates often 

 take part in the formation of the cup, and are called the anal 

 plates. 



