The assumed Relationship of Parkeria to Stromatopora. 353 
XL.—WNote on the assumed Relationship of Parkeria to 
Stromatopora, and on a Microscopic Section of Stromatopora 
mamillata, fr. Schmidt. By H. J. Carter, F.R.S. &e. 
In 1877 (‘ Annals,’ vol. xix. p. 55 et seg.) I made it plain 
(at all events to myself) that Parkerta was neither a species 
of Foraminifera nor one of Spongida; and at p. 61 (¢b.) began 
to compare the structure of Parkerta with that of Stromato- 
pora, meaning that stromatoporoid organism of the Devonian 
Limestone called by Phillips “‘ Cawnopora placenta,” which 
was originally described by Lonsdale under the name of 
“ Coscinopora placenta.” But subsequently, that is in 1879 
(‘ Annals,’ vol. iv. p. 101 et seqg.), I found that Caunopora 
must be considered as an instance of “ symbiosis,” in which 
the vertical tubes belonged to one organism and the stromato- 
poroid mass in which they are imbedded to another, probably 
both allied to the Hydroida; thus my comparison of the 
“ vertical tubes”? of Caunopora with those of Parkeria be- 
came inadmissible, and the nature of the animal of Parkeria 
was still left open for conjecture. 
To assume that Parkeria was not a Hydroid because the 
skeletal structure of the former was probably calcareous and 
not chitinous would be equally inadmissible, because Hydrac- 
tinia calearea affords a living instance to the contrary, to say 
nothing of the fossil species, viz. H. pliocena (‘ Annals,’ 
1877, vol. xix. p. 50) and H. Kingw (db. 1878, vol. 1. 
p- 301), both of which are of considerable thickness. Thus, 
prevalent as the chitinous skeleton is among the Hydroida, 
there are instances of calcareous ones in which the structure 
mutatis mutandis is the same; but to this I shall presently 
recur more particularly. 
Meanwhile fossil specimens of massive Polyzoa from the 
Coralline Crag of Suffolk have been presented to me to show 
how much their general form, structure, and mode of growth 
resembles that of Parkeria; that is, they are hemispherical 
masses with nodular segmented surface, radiating structure, 
and concentric lines of intervals or chambers (analogous to 
the “ chamberlets’”’ in Parkeria), all growing from a central 
point and furnished with an epithecalinvestment. But, while 
the segments are composed of little groups or masses of parallel 
tubes in juxtaposition, which groups are separated in the direc- 
tion of the radiation by the intervening of the ‘ chambers,” 
and each mass is based upon an epithecal layer of amorphous 
substance which extends more or less up the sides, thus form- 
ing the ceiling of the empty “ chamber,” whose floor, on the 
