190 REPORT—1883. 
appear without doubt to be Cyclostomatons, and I have therefore ventured 
to appropriate his expressive appellation for the fenestrate forms of 
Hornera; not regarding it, however, as impossible that the fossil genus 
Fenestella may have a prior claim after all.’ 
Through the kindness of Miss Gatty I have been allowed to examine 
her collection of Polyzoa, amongst which is a beautiful specimen of 
R. foliacea, McGillivray. If this species may be taken as the type of 
Retihornera, none of the species of Fenestella known to me could be, even 
provisionally, associated with it. In some of the branches we have a 
triple and even a quadruple set of pores, and ouly in some rare cases are 
pores biserial in their arrangement. It may happen, however, when I 
come to treat of Tertiary fenestrate Hornera, that these may be associated 
with the more ancient Phyllopora in the family Polyporide; but even 
then I think that the group or groups should be kept distinct. 
Mr. Shrubsole ! has already pointed out the differences in the external 
characters of Silurian and Carboniferous Fenestelle. It only remains for 
me to show that the structural differences are very slight indeed. The 
cells in all Fenestelle are arranged bi-serially, and between the cells there 
are very delicate interspaces, the walls of the cells in the opposite sides 
of the branches being separate and distinct. Yet by means of this inter- 
space the whole of the cells of the colony appear to be linked together. 
Have we here the passages through which the endosare passed from cell 
to cell? If so, then the unity of the cells in the colony, and also the 
distinct surroundings of the cell by its own wall, and the purpose of the 
interspace, are easily explained. 
In Ptilopora, M‘Coy, the arrangement of the cells is very similar to 
that of Fenestella, but it is difficult to obtain specimens for making sections. 
I purposely keep the genus distinct, subject of course to future correc- 
tion on account of its peculiar zoarial characters. Mr. Ulrich includes 
in his family Fenestellide the following genera :— 
Fenestella, Lonsdale. Archimedia, Lesueur. 
Polypora, M‘Coy. Lyropora, Hall. 
Septopora, Prout. Carinopora, Nicholson. 
Fenestralia ,, Oryptopora, o 
Phyllopora, King. Ptilopora, M‘Coy. 
I have been compelled to founda new genus for Carboniferous species 
formerly included in Glauconome, Goldfuss. I should, however, have 
preferred to adopt the old names of King—Acanthocladia, or Pennirete- 
pora, D’Orb.—but neither of these genera conveys a just idea of the species 
which have been discovered since these names were formulated. Acantho- 
eladia is a Permian fossil of the family Thamniscide, and the type of the 
genus, A. anceps, Schlotheim, has ‘rows of cellules from three to six 
on the stems’ (op. cit. p. 48), and the type of D’Orbigny’s Penniretepora 
is Glauconome disticha, Lonsdale. 
FENESTELLA. (Restricted.) 
‘Zoarium a calcareous reticulate expansion, either flat, conical, or 
cup-shaped, formed of slender bifurcating branches, poriferous on one 
face, connected by non-poriferous bars, forming an open network, 
Zocecia immersed in the branches, and arranged in two longitudinal rows 
1 Brit. Upper Sil. Fenestellide, Quart. Journ. Geo. Soc. 1880, p. 242. 
