168 DEVONIAN FAUNA. 



Affinities. — The present species is really much nearer to Fenestella plebeia, 

 M'Coy ; l but, judging both from his description and figures, and from some well- 

 preserved Carboniferous specimens from the Halkyn Mountains, I think there can 

 be no doubt that they are perfectly distinct. F. plebeia is flabellate or fan-shaped 

 instead of infundibuliform or cup-shaped, the branches are coarser and straighter, 

 the cell-mouths larger, and the carinas very much stronger. The bifurcations also 

 seem to occur more nearly at the same level in different branches, the dissepiments 

 seem slighter, and the fenestrules longer and narrower. It may be remarked, 

 on the other hand, that in all the points that are observable, as well as in its 

 measurements, the common Pilton Fenestella agrees with these Carboniferous 

 specimens, and therefore I have no doubt that M'Coy is correct in identifying that 

 North Devon form as F. plebeia. Shrubsole ~ regarded F. plebeia as the equivalent 

 of G. antiqua, Goldfuss. 



The other Carboniferous species described by Phillips or M'Coy, which are 

 at all similar in other respects, may be distinguished by their much stronger carinas, 

 except F. hemisphgerica, 2, which is very much smaller in structure. 



F. explanata, F. A. Romer, 4 which is identified by its describer with F. antiqua, 

 Phillips (not Goldfuss), seems distinguished by its much stronger carina?, stouter 

 dissepiments, and perhaps by the wavy margins of its branches. 



F. microflora, F. A. Romer, 5 of the Iberger Kalk, is much more like it. Romer 

 defines it as having the branches as wide as the dissepiments, three or four small 

 cells to a fenestrule, and a conical zoarium. This is, however, but little for specific 

 discrimination, especially as the size of the fenestrules is not given ; the latter, 

 moreover, seem shorter and squarer than in the English species, so that it does 

 not seem safe to identify them without further evidence. 



Of the American species given by Ulrich none approach it at all closely. 

 Perhaps the nearest is F. modesta, Ulrich, 6 but it has slighter branches, smaller 

 fenestrules, and a granulated external surface. 



From the common Pilton fossil, F. plebeia, it appears to be distinguished by 

 its rather coarser network, less straight branches, and probably less prominent 

 pores. 



1 1844, M'Coy, ' Syn. Carb. Foss. Ireland,' p. 203, pi. xxix, fig. 3. 



2 1880, Shrubsole, ' Quart. Journ. Geol. Soc.,' vol. xxxvi, p. 242. 



3 1844, M'Coy, ' Syn. Carb. Foss. Ireland,' p. 202, pi. xxix, fig. 4. 



4 1850, P. A. Romer, < Beitr. Harz.,' pt. 1, p. 7, pi. i, figs. 12 a, b. 

 I 855, ibid., pt. 3, p. 34, pi. vi, fig. 2G. 



fi 1890, Ulrich, ' Geol. Surv. Illinois,' vol. viii, p. 550, pi. lii, figs. 3—3 b. 



