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paljEontology op new-yoek. 



specimens the central portion, or that included within the cup and rays, is crj'stalline, and 

 weathers less rapidly than the lamellae and walls of the cell, which are consequently worn down ; 

 and the rays which appear upon the surface are the crystallized spaces between the lamellae, 

 which, from the margin of the cup having been obliterated, often extend indefinitely outwards, 

 and become nearly or quite confluent with those of the adjoining cells. This is a very com- 

 mon character, and one at the same time liable to mislead an inexperienced observer. 



In the same specimen, it often happens that the openings of the cells present a very different 

 appearance ; the centre of the cell being depressed, and the rays reaching to it, still without 

 defined outer margins. In others, and often in connexion with the first described characters, we 

 find the open cells with twelve short rays, the margin or walls of the cell elevated, and each 

 one standing separate and distinct. These, with other varieties of character, are due to the 

 state of preservation of the coral, and the influence of weathering upon crystalline and un- 

 crystalline, siliceous or calcareous masses of the coral. In some of the more solid specimens, 

 the intercellular spaces present oval or irregular points like minute tubular openings, which 

 lie parallel to the principal tubes. 



In specimens that are siliceous, and sometimes in calcareous specimens, the tubes stand out 

 separately and disconnected except by a few transverse dissepiments at irregular intervals, 

 while in others the interspaces seem filled with parallel minute cylindrical tubes. 



Aside from the varieties of character presented from the causes here mentioned, there is 

 sometimes that resulting from the difference in size of the tubes, and the different distances 

 from each other, owing to an increase of the intercellular spaces. I am unable, however, to 

 discover any positive characters by which species may be separated, and I have therefore in- 

 troduced the principal varieties of form and appearance under one specific name. 



Fig. 2 a. A calcareous mass where the interstices between the rays are crystallized and promi- 

 nent, the entire surface presenting a confused stellate appearance. 



Fig 2 h. A portion of the same enlarged, showing more definitely the limits of the stellate cells 

 and the intercellular lamellar or granular surface. 



Fig. 2 c. Several of the cells near the base of the same specimen enlarged, showing a different 

 appearance from 2 b. In these cells the centre is depressed. 



Fig. 2 d. A vertical section of the small specimen fig. 2 a. 



Fig. 2 e. A portion of the same enlarged, showing the spiniform ascending raj^s in the cell and 

 the transverse septa in the interspaces. In this and numerous other specimens, 

 there is no appearance of transverse septa in the longitudinal sections of the cells. 



Fig. 2 /. A figure from a polished piece of crinoidal limestone, showing a nearly transverse 

 section of a spheroidal mass of this coral, with a vertical section of another indi- 

 vidual which apparently commenced growth upon the preceding one. On the right 

 hand is a vertical section of a smaller species, also growing on the first. This surface 

 presents beautiful stellate cells, with twelve rays, and interspaces with dark oval 

 spots like tubular openings. 



Fig. 2 g. This figure is enlarged from the surface of the polished specimen, showing the cha- 

 racters very distinctly. 



