86 
VIXE : NOTES ON YOKEDALE POLYZOA. 
Family Polyporidge. 
1883. Fouith Brit. Assoc. Report, Fossil Polyzoa (Mihi). 
Xoarium forming' large or small fenestrated expansions. 
Zocecia contiguous in section, with three rows and upwards of cell 
apertures in the branch, opening on one side only. Branches united 
by dissepiments or by anastomosis. 
Genus Folypoi-a, M'Coy. 
,, Phyllopora, King. 
Genus Polypora, M'Coy. 
Zoarium a delicate or robust reticulated calcareous expansion, 
branches round, connected by dissepiments. Zoacial apertures 
circular or pyriform, with from three to five rows of cells in a branch : 
marginal cells occasional projecting. 
Several species of Carboniferous Polyporge have been described 
by authors, but those which have been heretofore found in British 
rocks, are named either in accord with the descriptions of Prout or 
of M'Coy. Prout in the Trans. Acad., St. Louis, Vol. I., p. 449, pi. 
18, fig. 3, described and figured a species which he named 
FtJi/pora tuherculata^ (examples of which are before me), and one of 
the characters is the peculiar tuberculation of the obverse face. 
This was pointed out by Mr. John Young, in a paper on Scotch 
Poli/j^ora communicated to, and published in the Geological Magazine 
(lcS74); and again in a brief note* — accompan3ang- two slides — Mr. 
Young' makes reference to Prout's species. 
Many of the differences between the Scotch and the Iiish 
Polypora^ were pointed out b}^ Mr. Young when he preferi-ed to 
re-christen the Scotch form and name it P. tuherculata^ Prout. The 
differences between the Scotch and the American examples maj^ now 
be restated. In the American species of Polypora tuherculata, Prout, 
the fenestration is different, there are from four to five cells on each 
side of the fenestrule ; in Scotch examples I count from five to ten or 
even more. In Prout's species the dissepiments, on the whole, are 
likewise different, in the one case short, stunted, and at fairly 
* Tran. Gool. Soc, Edinburgh (1874), p. 401. 
