from Iceland and Labrador. 1 1 1 



what massive mucro, as broad as the mouth and stretching 

 back for some distance over tlic wall of the cell ; it bears on one 

 side an aviculariuni with rounded mandible, directed upwards. 

 The surface of tiie cell is smooth, but often traversed hy ribs 

 which radiate from the margin and are canicd up as prominent 

 keel-like lines to the apex of the rostrum. The ovicell is semi- 

 circular, and, in an early stage at least, without punctures. 

 Within the inferior margin there is a small denticle. 



The cells iiave a very crowded appearance, and are more 

 erect than those of either G. plicata or C. ovata. The mucro 

 is central (that is, the apex corresponds with the centre of the 

 inferior margin, and the base spreads out equally on each side), 

 while in the two last-named species it is placed completely on 

 one side of the cell. 



12. Cellepora bilammata, n. sp. (PI. XI. figs. 6, 7.) 



Amongst the Labrador dredgings there is another form 

 referable to the same group as the above, but presenting 

 some marked and distinctive peculiarities. It occurs in two 

 very difterent conditions. In one (a) the cells are rather 

 crowded, ovate, suberect, the surface smooth ; mouth orbicular, 

 the peristome rising on each side into a mucronate process, one 

 of the two (and occasionally both) bearing on its side an avi- 

 cularium with rounded mandible ; between the two processes 

 there is a rather wide cleft, and immediately within it a small 

 denticle (PI. XI. fig. 6). Occasionally there are traces of the 

 formation of a second calcareous lamina over the primitive 

 cell-wall. Cells occur in which the second envelope has only 

 partially overspread the original wall, and the edge of the later 

 growth can be distinctly traced. 



In the other condition in which the species appears (h) almost 

 every cell exhibits the double lamina, the later process of cal- 

 cification being only partially effected (PL XI. fig. 7). In this 

 state there are no avicularia. The processes on the inferior 

 margin are both simple extensions of the primitive lamina, 

 somewliat rounded at the top and separated by a broad cleft. 

 With the growth of the second lamina they would assume their 

 perfect mucronate condition ; and the development of the avi- 

 cularium (or avicularia) would probably follow. The ovicells 

 are developed plentifully on this form ; they are semicircular 

 almost truncate in front, partially concealed by the ascending 

 marginal processes, smooth, with a few rather large punctures 

 on the front. I have not noticed this doubling of the cell- 

 wall in any of the kindred species, while the character of the 

 mouth is vcr}' distinctive. 1 have therefore thought it best to 

 give this form a separate name. 



