G. R. Vine—Carboniferous Polyzoa. 509 
All the Carboniferous species that have been referred to this genus 
have cells on both sides, and, as I have already referred one of the 
accepted species to another genus, I will deal now with the Sulcorete- 
pora Robertsoni, Y. and Y. As there are characters in this species 
altogether different from any known species of Ptilodictya, the same 
reference for this, as appears feasible for Flustra ? parallela, Phill., 
is altogether out of the question. The S. Robertsoni has none of the 
characters in common with Phillips’s species, and I should strongly 
recommend the Messrs. Young to construct for this typical species 
anew genus, especially so as ‘“‘ Between each pair of cells in a longi- 
tudinal series, 1 to 3 pores occur, normally above each cell-aperture, 
and in well-preserved specimens tubercles surround each cell-area 
more or less completely.” ! The facies of Phillips’s species and the 
species of the Messrs. Young may at first sight appear identical, but 
the forms described by the later authors are destitute of the non- 
poriferous, rugose, and striated margins of Flustra? parallela. It 
is upon the presence of this particularly constant character that I 
refer Phillips’s species to Ptilodictya. 
Archeopora nexilis, De Koninck. 
This genus and species, classified as it is with the Polyzoa, isa 
most peculiar one. I have not by me De Koninck’s work for refer- 
ence, and the remarks that I may offer upon the species—for I shall 
accept the genus without discussion —are the results of original 
investigation. The species is tolerably common in a few localities 
of Scotland. JI have no record of it in this country except in doubt- 
ful fragments in Wales—and my type specimen was presented to me 
by Mr. John Young, and I believe I may safely conclude that this, 
with other specimens, was seen and approved of by De Koninck 
when he visited the Hunterian Museum of Glasgow. 
Sp. Char.—Polyzoary adherent to stems of encrinites, shells, frag- 
ments of Rhabdomeson, Ceriopora interporosa, spines of Mollusca, etc., 
spreading irregularly, forming large patches, at other times mere 
minute specs; pores generally oval, separated from each other by 
smaller openings. I cannot call them ‘interstitial or caenenchymal 
tubuli ’—for that would convey a false impression, for pores and 
cells are netted together. The number of small openings surround- 
ing a cell varies; sometimes there are as many as fifteen, in other 
places not more than five or seven. About twelve cells with their 
interposed pores occupy the space of a line and a half across the 
cells, from nine to ten in the same space in their length. The poly- 
zoary is separated from the foreign objects to which it is attached by 
avery thin lamina formed by the bases of the cells. There is no 
evidence of tabule in thin sections, but the interjacent pores do not 
reach quite to the bases of the cells. I have never seen a specimen, 
on which a fresh colony is found spreading over an older one, but 
sometimes a colony of Stenopora is found upon the polyzoary of 
Archeopora. In a thin transparent section of a small fragment of 
another specimen, adherent to a portion of shell, a most peculiar 
1 Ibid. p. 167, 
