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60 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



In the Paleozoic rocks we have considerable evidence going to show 

 that the Crinoidea became detached from their roots or disks of 

 cementation at various stages in their development. In a very great 

 number of cases it seems quite certain that these residual roots as 

 we find them do not indicate the death and disintegration of the 

 crinoid, but rather a separation of the crinoid from its point of attach- 

 ment during the life of the individual. In some cases, at least, dis- 

 ruption seems to have been voluntary, resorption apparently taking 

 place at the point of detachment. 



In certain formations — the Hamilton for instance — one is accus- 

 tomed to see large numbers of calcareous disks attached to brachio- 

 pods, corals, crinoid stems, and every conceivable support. Each of 

 these disks has a stem cicatrix, and at one time obviously consti- 

 tuted the distal extremity of a pelmatozoan column. As a rule these 

 basal expansions are small, ranging from 2 to 5 mm. in diameter. 

 The stem cicatrix is seldom sharply defined, showing that there was 

 probably a partial resorption of the stereom at the junction of the 

 disk and column. It is evident that these disks pertain to young 

 crinoids and are directly comparable in function to the so-called 

 "dorso-central" of Antedon. It is equally evident, I think, that 

 these young crinoids became detached and shifted to another locality 

 where they may or may not have become permanently anchored. 



An interesting locality where such basal disks are particularly 

 plentiful is in the Trenton limestone of Kirkfield, Ontario. Here at 

 one time the sea advanced over an eroded limestone surface. With 

 the advancing sea, and probably in very shallow water, came in 

 large numbers of crinoids. The old limestone bottom is covered with 

 basal disks, as many as fifty having been counted in an area of a 

 square foot. Most of these disks are small, but occasionally the 

 highly specialized basal expansions of Oleiocrinus are found, rangmg 

 up to 5 or 6 cm. in diameter. In many cases it seems probable that 

 the crinoids became voluntarily detached. Stems and crowns are 

 rarely associated with these basal expansions, and frequently the zone 

 of detaclrment shows signs of resorption. It may be argued that 

 instead of being a case of resorption in these instances it is a case of 

 partial solution of the calcareous matter subsequent to the violent 

 disruption of the column from the base. The splendid condition of 

 such crinoids as are found at this horizon where the most delicate 

 ornamentation is beautifully preserved, and the unaltered sharp 

 angles of broken columns tend to refute this argument, however. 

 Another example of this sort is in the Silurian of Waldron, Indiana. 

 Here in one bed are found great numbers of crmoid roots, most of them 

 probably belonging to Eucalyptocrinus. Stems and crowns, again, 

 are rarely associated with these roots. It seems probable that here 



