CARBONIFEROUS FENESTELLID®. 283 
Fenestella arctica, var. scotica, Ether., jun., is a recent addition to 
the list *. It is unfortunate that in neither the species nor variety 
was the poriferous face in a condition to admit of description. In 
the absence of all reliable specific details they must be regarded as 
doubtful. I have previously given my reasons for believing that 
Fenestella arctica, Salt.7, 1s the. last stage of Fenestella plebeia, Mt Coy. 
Tn this view I am eoatemed by the examination of some specimens 
from the shales of High Blantyre. 
Here occurs a species which on the reverse answers fully the 
description of Hvnestella arctica, Salt. On lifting this reverse from 
the shale by the process made known by Mr. John Young, F.G.S., 
the obverse is seen to have the true characters of Fenestella plebera, 
M‘Coy, and with scarcely a trace of the zigzag markings which on 
the reverse serve the purpose of a bracket under the dissepiment to 
support the increase of growth in the polyzoarium. 
Fenestella Morrisii, M‘Coy +, in the Woodwardian Museum, is in 
a condition that defies specific definition. It is often found in the 
Carboniferous strata that water has removed the whole or part of 
the organic remains. In the case of Fenestella the first portions to 
disappear are the thin dissepiments, leaving an irregular number of 
pores between the remaining dissepiments. Both Fenestella Mor- 
visti, M‘Coy, and LIenestella quadradecimalis, M‘Coy §, I believe, 
have originated in this way. This is partly borne out by what 
Prof. M‘Coy says of Fenestella Morrisiz, “ dissepiments thin, often 
disappeared.” 
The interstices and dissepiments of Lenestella quadradecinalis, 
M‘Coy, are also described as thin, evidently water-worn. ‘The ex- 
planation of these forms probably is that Fenesteila Morristi, M‘Coy, 
is a fragment of Menestella plebeia, M‘Coy, from which alternate dis- 
sepiments have been removed. In Menestella quadradecimalis, M‘Coy, 
the same thing has occurred to Fenestella polyporata, Phill., giving 
twice the usual number of pores between the dissepiments. This 
loss of dissepiments in /nestedla is a very ordinary occurrence, and, 
in the case of fragments, likely to mislead, as the means of correc- 
tion are not to hand. Hall figures a Fenestclla (prisca) with the 
dissepiments absent There still remain unnoticed Fenesiclla 
oculata, M‘Coy, Fenestella cjuncida, M‘Coy, and Ienestella varicosa, 
M‘Coy. ‘They are mostly unknown to the most diligent workers 
among the Polyzoa. Small picces may be found haying more 
or less divergent features; but it is a question whether these are 
distinct species or mere variations in growth, such as often occur 
on large fronds, and in so marked a manner that, by the same rule, 
two, three, or even four supposed species might be made out of a 
portion only of the polyzoarium. It is significantly said of Wenes- 
tella oculuta by Prof. M‘Coy that it “ occurs only in fragments.” 
* Ann. & Mag. Nat. Hist. ser. 4, vol. xx. p. 31. 
: Belcher’s Arctic Voyage, 1855, vol. ii. p. 385, t. 36. fig. 8, 
{ Syn. Carb. Foss. Ireland, pl. 28, fig, 14, 
g Ibid. pl. 28. fig. 13. 
I Hall's Palxont. New York, vol, ii, pl, xix, fig. 44, 
