320 [Jan. 17, 



moreover, it is bounded, at the distal extremity, by a broad flat 

 band which is extended around the whole jjeriphery of the cell ; 

 while in Dr. Morton's coral the surface slopes inwards from the 

 very edge of the cell. 



These differences are not pointed out under the supposition that 

 Dr. Morton conceived the two corals might be identical, for he was 

 clearly aware of their distinction, but because both the Maestricht 

 and Timber Creek deposits are members of the Cretaceous series, 

 and the perfect agreement in generic outline with Goldfuss's figure 

 (14 a), might lead a less careful observer than Dr. Morton to the 

 inference, that the fossils are specifically the same. 



The branches preserve a considerable uniformity of breadth, 

 expanding only towards their bifurcation, and there very slightly, 

 in consequence of the addition of one or more lateral rows. They 

 diminish in thickness towards the edges, where they are rounded. 



The cells on the opposite side of the medial line agree generally 

 in position, and those forming the surface of the branches have a 

 great regularity in size and relative proportions ; but, at the point 

 of bifurcation, and along the edges of the branches, small and im- 

 perfect cells may very frequently be observed, the latter exhibiting 

 sometimes irregular pores in the external covering. 



Of the earliest state of the cells no evidence was obtained ; and 

 of the condition after the formation of the side-walls only one case 

 was noticed. It consisted (a, b) of a portion of a main branch, 

 with part of another springing from a bifurcation. The surface 

 of the greater number of the cells was wholly open, indicating 

 considerable rapidity of development, or slowness in the formation 

 of the exterior ; and in only a few instances was there a commence- 

 ment at the proximal extremity of the outer surface. The walls 

 of the latest produced cells, or those at the superior extremity of 

 the bifurcated branches, had a sharp edge without any line of 

 separation ; but in the cells of the undivided branch, and where 

 the development of the external covering had commenced, fine 

 grooves were perfectly visible. This great production of imma- 

 ture cells is analogous to many well-known recent examples. 



In what was believed to be another step towards maturity, the 

 surface of the cells was considerably developed, but the mouth was 

 not regularly defined, the open part being large and circular. The 

 structure of the mature cells is given in figure d, and in the 

 specific characters. 



The passages from maturity to what may be termed a state of 

 decrepitude afforded some interesting structural details. In the 

 first steps, the fine separating grooves between the cells were par- 

 tially or completely obliterated, and a general thickening of the 

 parietes was noticed ; but these changes were not always most 

 decidedly shown in the oldest cells of the branch, depending, ap- 

 parently, in part upon the individual polype. In a specimen in 

 which the above alterations were not so complete as in other 

 cases, there appeared upon the surface of the cells several minute 

 prominences, and one or two fractured vesicles. Some of the 



