SECONDARY AND TERTIARY FORMATIONS OF NORTH AMERICA. 151 



Colony sometimes in broad tortuous plates, sometimes in narrow dichotomous branches, 

 composed in its very young state of but two layers of cellules, placed back to back, a 

 true Esdiaripora, but almost immediately followed by several succeeding layers. Cel- 

 lules elongated oval, generally in regular quincunx and always in close contact all 

 round, sides usually straight, sometimes, especially in the later layers, quite convex. 

 Mouth terminal, small, round to subquadrate, narrowest at the proximal end, where 

 it is occasionally, abruptly constricted, lip simple. Special pores two, minute, placed 

 at the distal angle of the cellule, and sometimes surrounded by a delicate thickening, 

 at other times simply pierced. Surface marked by seven or eight pairs of very minute, 

 but elongate, transverse fossets. Ovarian vesicle large, as broad as the cellule, not 

 prominent, usually overlapping the proximal end of the succeeding cellule, and broadly 

 emarginate at the oral edge. 



The variable mode of growth of this species is worthy of notice. Morton described 

 the lamellar variety. This was also the form noticed by Lonsdale. We have it abun- 

 dantly from near Mullica Hill, N. J., in thick, tortuous anastomosing plates, with a 

 wholly different appearance from Dr. Morton's specimen, and which we should have 

 considered as another species, were it not for the identity of the cellules. Another 

 widely different form occurs at both localities. It is rather broad, flattened branches, 

 probably anastomosing by their edges in nearly the same plane, somewhat after the 

 manner of Relepora. The second, third, and subsequent layers, are not always con- 

 formable in direction of the cellules with the first. This is most obvious in the 

 dichotomous varieties, when, sometimes, the lines of cellules in successive layers, are 

 at right angles. 



We have counted, in one case, nine layers in a transverse section. The only con- 

 stant character in this species, as will be seen from the above observations, is the 

 cellule. This, however, will serve at once to distinguish it. It will be well to men- 

 tion, that only on well preserved specimens can we detect the transverse fossets. 



From the Cretaceous of Timber Creek, and Near Mullica Hill, N. J. 



REPTESCIIARIPORA, d'Orb. 1851* 



Colony composed of a single layer of cellules arranged in longitudinal lines and 

 quincunx, always encrusting by its whole under surface. Cellules provided by two or 

 more special pores around the mouth, and with the surface posterior to the mouth 

 pierced by numerous fossets arranged in opposing pairs. 



With cellules like in Esdiaripora, this species can be readily distinguished by its 

 being always encrusting and composed of but a single layer. 



R. maeginata, n. s., fig. 35. — Colony composed of a single layer of encrusting cel- 

 lules. Cellules placed in regular lines and in pretty regular quincunx, sometimes 

 slightly separated ; form oval, rarely with the sides approaching a straight line. 



39 



