FENESTELLA. 187 



zoarium was iufundibuliform, either from its developing from a central base or 

 from its sides overlapping each other. In these fossils the poriferous face. of 

 the branches is external, and in one of them it appears to show a thin keel. 



(2) In a second specimen in the Museum of Practical Geology, however, the 

 poriferous face appears to be upon the concave (or internal) side of the zoarium. 

 This fossil is a mould, and is remarkable for having circular cavities, not quite as 

 numerous as the fenestrules, irregularly placed on its branches, which they equal 

 in width. Whether these cavities indicate spines, as in F. Lyelli, Dawson, 1 or 

 ovarian capsules or nodes such as are described in the very similar F. vera, 

 Ulrich, 2 does not appear. The specific identity of this specimen must evidently 

 be at present doubtful, unless the appearance of the inner face being poriferous is 

 deceptive. 



In the other specimens the number of cells to a fenestrule is sometimes two, 

 sometimes three, while sometimes (unless a dissepiment has been obliterated) it is 

 four. In one or two specimens which seem to belong to the same species, but 

 which are in a different state of preservation, and perhaps more nearly resemble 

 F. plebeia in some points, their number is clearly three or four. 



Affinities. — F. nodulosa, Phillips, 3 appears to be a closely allied form, resembling 

 our typical specimens in the prominence of the cell-mouths, which nodulate the 

 sides of the branches. Possibly its cells were as a rule slightly more numerous, 

 and its fenestrules wider. Among numerous examples of it in the Woodwardian 

 Museum are two which show its frond to be flabellate, as described by M'Coy 4 

 (though Phillips called it" radiating," and so figured it). For this reason it seems 

 safer to regard it as distinct. 



F. oculata, M'Coy, 5 also is very similar, but appears to branch more rarely, to 

 have no keel on the poriferous face, and to be smooth on the reverse. In these 

 points, perhaps, F. fiabellata, Phillips, 6 is still nearer, but its branches seem to be 

 slighter, and its fenestrules more regular ; it was regarded by Shrubsole as 

 synonymous with F. membranacea, Phillips (i. e. Hemitrypa hibernica, M'Coy). 



M'Coy mentions that in H. hibernica there are large irregular spines on the 

 inner face. The fact that the external face is poriferous, and other resemblances, 

 may possibly indicate that our species is really a Hemitrypa, but at present there 

 is no direct proof that it is so. The prominence of the pores, at all events, 

 distinguish it from H. hibernica as well as from H. oculata, Phillips. 



1 1879, Nicholson, ' Manual Palieont.,' vol. i, p. 420, fig. 262. 



2 1890, Ulrich, ' Geol. Surv. Illinois,' vol. viii, p. 535, pi. xliv, figs. 1,1 a; and pi. liv, fig. 3. 



3 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 199, pi. i, figs. 31—33 ; and 1881, Shrubsole, ' Quart. 

 Journ. Geol. Soc.,' vol. xxxvii, p. 183. 



* 1844, M'Coy, ' Synops. Carb. Foss. Ireland,' p. 203. 



5 Ibid., p. 203, pi. xxviii, fig. 15. 



6 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 198, pi. i, figs. 7—10. 



BB 



