ON FOSSIL POLYZOA. 189 
ranging in parallel, transverse, or oblique rows on each side of a mesial 
line.’ 
Upper Chalk . Idmonea Comptoni, Mantell. 
ee F : »  eretacea, Milne-Kd. 
a . ; »  gradata, Defranc. 
Family III. Fernesreriipz. (Restricted.) 
Zoarium forming large or small fenestrated or non-fenestrated expan- 
sions. Zowcia arranged biserially in the branch, tubular, but slightly 
truncated at the distal extremity ; orifice circular, opening on one side 
only. Branches united by dissepiments, or free. 
Genus Fenestella, Miller & Lonsd. Accepted type, F’. plebia, M‘Coy. 
» LPtilopora, M‘Coy. - P. pluma, M‘Coy. 
» Linnatopora, Vine. 95 P. elegans, Young & Young. 
In 1849 Professor King established this family for a very peculiar 
group of Paleozoic Polyzoa. ‘Considering Fenestella as the type of the 
family, it is proposed,’ says the author, ‘ to include in it all those reticu- 
lated genera agreeing with this genus in having the cellules planted on 
a basal plate composed of vertical capillary tubes, as first discovered b 
Mr. Lonsdale. Besides Fenestella this family embraces the Ptzlopora 
and Polypora of M‘Coy ; also the genera Synocladia and Phyllopora,’ } 
It is very evident that if we relied upon the above diagnosis it would 
be impossible to accept King’s family name for the restricted group 
which I have placed under this head. As Fenestella was taken by Pro- 
fessor King as the type, I prefer to use the name, and restrict the group 
to those species only in which the cells are arranged biserially in the 
branch. 
The genus Fenestella has been so ably handled by Mr. G. W. Shrub- 
sole,” and so recently, that I think it needless to enter upon any lengthy 
description here. Accepting Mr. Shrubsole’s work, I will now give 
reasons for allowing this family to follow that of the Tubuliporide. 
If we take any ordinary Fenestella, such as F. plebeia, M‘Coy, we 
shall find that the branches bear two rows of cells, separated, apparently, 
by a median keel, A vertical section of the branch shows that the cells 
are arranged in a line, but that the proximal part of the cell is depressed, 
the distal portion rising upwards to the surface of the branch. <A 
transverse section shows that the cells are alternately placed, that the 
keel is obliterated, and that the cells themselves are foraminated very 
similarly to the cells of recent Crisia, Stomatopora, or Tubulipora. There 
are also minute structures in these ancient cells, very similar to minute 
structures in recent species of Cyclostomatous Polyzoa. The capillary 
tubes referred to by Mr. Lonsdale are also a peculiar feature in the 
zoarium of Fenestella—that is, if I understand his reference aright— 
and are totally unlike any of the minute structures in Retepora, where, 
as Mr. Lonsdale says, ‘capillary tubes are wanting.’ In Mr. Busk’s 
‘Cyclostomata’ (p. 20), the following reference is made, for classifica- 
tory purposes, to Fenestella:—‘ Herr Kirchenpaur’s genus Retihornera 
would, from his description, include some Escharidan or Cheilostomatous 
forms approaching Retepore ; but among them his R. dentata and plicata 
1 Permian Fes:. King, p. 54. 
? Quart. Jour. Geo. Soc. May 187°, Nay 1880, May 1881. Three papers. 
