226 



PALEONTOLOGY OF NEW-YORK. 



body above, but from having that column enclosed at three points by corals of dif- 

 ferent species, which could only have grown about it during its upright position, and 

 during the lifetime of the animal. The upper coral upon this column, e (e+ the en- 

 largement of some of its cells), is the Astrocerium parasiticum ; and this example 

 furnishes an explanation of the manner in which many larger specimens of this 

 species of coral are found, enclosing the stems of crinoids. It is probable that in many 

 instances the growth of those corals to a large size aided in the destruction of the 

 crinoid, by the increased size and ponderous nature of the mass enclosing the slender 

 column. 



At the points /and g (enlargements of the same in /+ and g+*), are two other 

 corals of the Genus Trematopora, which, from their more minute structure, were 

 probably of slower growth than the Asteogerium. These are often found enclosing 

 fragments of crinoidal columns, as shown in Plate 40 A. 



Fig. 1 b. A portion of the column enlarged, showing the edges of the joints quite smooth and 

 flat. This character prevails throughout the whole length of this specimen ; but it is 

 not the prevailing feature in this species, though not uncommon. 



Fig. 1 c. View of the end of the column, showing the articulating striae reaching to the canal. 

 This feature of the articulating surface has not been seen in any other individual ; 

 though all those examined, with this exception, have been from near the upper ex- 

 tremity. 



Fig. 1 d. A specimen having a small univalve shell attached, with its aperture setting closely 

 down upon the summit, and covering the mouth of the crinoid. The shell could 

 scarcely have assumed this position by accident ; and it was probably thus enclosed 

 within the arms of the crinoid while the animal was in a living condition, and the 

 accidents which have subsequently removed the column and arms have left the shell 

 adhering. 



Fig. 1 e. The summit of a specimen of medium size, showing the triangular form, the arrange- 

 ment of the arms, and position of the mouth. Connected with this figure, are some 

 enlargements of the plates at the base of the arms. 



Fig. 1 /. An individual of medium size, nearly globular in form, marked by strong ridges parallel 

 to and between the rows of pores, with intermediate strong tubercles. The ridges 

 • are so strong, and so intimately continuing into those of the adjoining plates, that 

 the line of separation is not conspicuous. The pores either open in elevated pustules, 

 or are imbedded in the sides of the strong ridges. I have not seen, in any other spe- 

 cimen, the ridges and tubercles so strongly developed. 



Fig. 1 g. The structure of Caryocrinus when spread out, showing the bilateral arrangement of 

 its parts as before described. The arrangement of the rows of pores dividing the 

 surface, particularly in its upper part, into rhomboidal areas, is likewise more clearly 

 shown in this figure. The plates are copied in detail from a specimen in the author's 

 possession, and the relative position of every part is preserved, as well as the arrange- 

 ment of the pores upon the plates, their openings in vesicular tubercles upon the 

 scapular and pelvic plates, and, in some examples, upon the costal plates. 



* The determination of these individuals is very difficult, from the surface being covered by a kind of pyritous 

 shale which can not be removed by any process. 



