Stone Lilies of the Trenton Limestone. 



49 



■lifTcrcnt species, and fringed on the inside with two rows oftentacula, which 

 most probably, with the arms, were used in capturing such food as the 

 crinoid subsisted upon- 



The stalk, at its lower end was attached to the bottom of the ocean, and 

 supported the animal like a flower upon its stem. Such is a general des- 

 cription, which will apply to all the true encrinites. When examined in 

 detail, however, the covering of a crinoid will be seen to consist of a 

 number of flat angular plates arranged according to a certain plan, and so 

 contrived as to constitute an external skeleton, with many moveable parts 

 attached to it, completely under the control of the animal, and exquisitely 

 iKlapted to the supply of all its wants. 





-^ig. 1 shews the skeleton of Glyptocrinus RAMiiLOsus dissected 

 and spread out upon a fat surface. In the centre, is 

 seen the circular upper joint of the column or stalk ; around it the 

 fve pelvic plates ; next, the fveFRiMARY Bays, of three plates 

 each, dividing into ten Secondary Rays, of four plates each, 

 and lastly, the bases efthe ttventyTEUTiATiY Rays, or free arms, 

 with a few of the tentacula attached. In one of the spaces are 

 seen the abdominal or Inteeradial plates. In the perfect 

 Crinoid, these are also found in the other four intcrradial 

 spaces. 



On dissecting one of those skeletons, it will be found that resting 

 immediately upon the top of the stalk there are one or more, (in the typical 

 species five,) small plates so arranged as to form a shallow saucer-shapc(.t 



