278 G. W. SHRUESOLE ON THD BRITISTT 
stella nodulosa, Phill., and <Actinostoma fenestratum, Young, the 
difference being due to preservation and to no other cause. 
An important question next arises, Is Fenestella nedulosa, Phill., 
peculiar in respect to these details, or are the features observable in 
Actinostoma common to all the Fenestelle? I think we have evidence 
in favour of the latter view. In several species I have noticed the 
prominent cell-pores; and in one instance I have traced the rayed 
cell-mouth as in Actinostoma as belonging to Kenestella plebera, 
MM‘Coy, also as having the prominences on the keel. 
In another species, Mnesteila polyporata, which Phillips figures 
without a keel, I have found it having a prominent keel with strong 
spear-shaped projections upon it. 
it is evident, therefore, that Fenestella nodulosa, Phill., is not 
alone in possessing the characters given to Actinostoma. 
There is an additional reason for thinking that this ornamenta- 
tion was common to all the Fenestellide, since the worn-down form 
of fenesiella nodulosa, Phill., in no respects differs from the other 
members of the family in a similar condition. It seems only fair, 
then, to believe that the bare and smoothed condition of most of the 
Fenestellide is due to attrition in the Carboniferous sea, which has 
destroyed all the prominences and delicate surface-markings, and 
that only in rare and exceptional cases have they escaped this 
treatment. 
It may be interesting here to notice that in an enlarged drawing 
of the poriterous face of Menestella tenuwiceps, Hall *, the interior of 
the cell-mouth, instead of being blank, is filled with a circular 
arrangement of fine points, evidently intended for organic structure. 
If so, then it may be that we have here a foreshadowing of the 
denticulate cell-aperture of Actinostoma. 
I propose to arrange the various described forms of Menestel/a under 
the following species. 
FENESTELLA PLEBEIA, M‘Coy. 
Fenestella antique, Lonsd., M‘Coy’s Syn. Carb. Foss. Ireland, 
p. 200 
F’, carinata, M‘Coy, Syn. Carb. Foss. Iveland, pl. 28. fig. 12. 
F, fiustriformis, Phill., Geol. Yorks. pl. 1. figs. 11, 12. 
F, wrregularis, Phill., Geol. Yorks. pl. 1. figs. 21, 22. 
F, formosa, M‘Coy, Syn. Carb. Foss. Ireland, pl. 29. fig. 2. 
F. tuberculo-carinata, R. Ether., jun., Mem. Geol. Surv. Scotl. 
sheet 23, p. 101. 
F, undulata, Phill., Geol. Yorks. pl. 1. figs. 16, 17, 18. 
This, which is the common species of the group, is individually 
more numerous than any other. In size of structure it occupies a 
position between Fenestella nodulosa, Phill., and Lenestella poly- 
porata, Phill. Its polyzoarium, in adult specimens, was from 
18 inches to 2 feet in circumference. Phillips found and figured 
* Hall's Paleont. N. York. 1852, pl. 40 D, fig. 2. 
