70 THE CRAG POLYZOA. 



uniformity consisting in the circumstance that occasionally one of the cells in a series 

 will give origin to two, from which are continued two distinct series, and so on. Thus in 

 Eschara the mouths of the cells are placed one above another in the longitudinal direction 

 of the series, and alternate with those of the contiguous series on each side. 



In Melicerita, on the contrary, the cells are disposed in transverse series, the summit of 

 each cell corresponding to the hne of junction of the cells in the series above ; so that the 

 mouths of the cells are opposite those on each side of them. As remarked by M. M. 

 Edwards, this constant difference in the disposition of the cells may be taken to represent 

 a corresponding difference in the organization of the animal. The peculiar disposition 

 itself is to be explained upon the supposition that the buds are thrown out in Melicerita, 

 not from the summit of the parent-cell, but from one side of the summit. 



Besides the Crag Fossil, I have been able to find only a single species referrible to 

 this genus, which thus appears to be of very limited importance. The species in question 

 is the Eschara Acasta of D'Orbigny (' Terr. Cret.,' pi. dclxii, figs. 7 — 9), which may be 

 presumed to belong to the Cretaceous period. 



1 . M. Charlesworthii, M. Edw, PI. X, fig. 4. 



Polyzoario foliaceo, explanato; cellulis marginatis, hexagonis, fronte linea elevata 

 utrinque ornata. Ostio transversali, semilunari, utrinque denticulato, dcntemque latum 

 bicuspidatum internum supra ostendente. Ovicellulis immersis, inconspicuis, apertura 

 semilunari in apice cellularum posita; aviculariis immersis inter cellulas sparsis. 



Polyzoarium foliaceous, expanded; cells with a raised border, hexagonal; orifice 

 transverse, crescentic, having a condyloid tooth on each side below, and a broad bicuspid 

 denticle within the upper border ; usually a raised line on each side of the front of the cell 

 which converge below ; scattered intercellular avicularia. Ovicells inuiiersed, incon- 

 spicuous, opening by a crescentic slit within the summit of the cell. 



Melicerita Ciiarlesworthii, M. Ed., 1. c. ; VOrhigny ; J. Morris, 



MeLICERTINA CUARLESTVORTIIII, Ehr. 



UiJDiUM Charlesworthii, 5. Wood. 



In this species, as well as in M. Acasta, D'Orbigny (sp.), the cells are bordered by 

 raised ridges, which subdivide the surface of the polyzoarium into hexagonal areas, as in 

 Salicornaria, with which, in some respects, the present genus would seem to correspond. 

 This character, therefore, might perhaps be admitted into the generic definition. The 

 mouth of the cell, which is placed about the middle of the hexagonal area, is crescentic in 

 form, transverse, and surrounded with a raised peristome ; within it, at the lower border, 

 will be obscrv^ed two condyloid teeth, like those often so much developed in Salicornaria, 

 and a broad bicuspid plate or denticle depends within the upper margin. On each side 



