VINE: NOTES ON YOKEDALE POLYZOA. 
93 
Section B. Zosecia radiating* in al' directions fi-om an imaginary axis. 
Genus, Reombopoea, Meek. 
1871. Pala!ontology, Eastern Nebraska. 
1884. Ulrich, Jour. Cincin. Soc. Nat. Hist., April. 
1885. Vine, Proceedings Yorks. Geol. Soc, Vol. VIII., p. 105. 
Type of Genus, R. lejndodendroidea, Meek, Up. Coal Measures, 
Nebraska and Wyoming. 
Zoarium ramose, branches slender. Zoacia tubular, radiating 
in all directions from an imaginary axis ; walls abruptly thickened 
, in the " matured " region, where the diameter of the visceral cavity 
is also more or less constricted. Zooecial apertures, circular or oval, 
placed at the bottom of more or less obviously impressed sloping 
rhomboidal to hexagonal vestibules." Ridges separating vestibules, 
spiniferous ; spines, hollow, often of two kinds, large and small, the 
latter most numerous, and surrounding the apertures in a single or 
double series, while the larger spines are usually developed only at 
the uppermost extremity of the cell. (Diaphragms [tabula, Nichol- 
son] generally absent, always few). Zooecial apertures frequently 
closed by centrally perforated operculee. Ulrich (op. cit., p. 2G). 
27. Rhombopora persimilis, Ulrich. 
Jour. Gincin. Soc. Nat, Hist, 188-4, p. 30, pi. I., figs la to Id. 
Ibid, Vine, Proceed. Yorks. Geol. Soc, 1884, p. 106. 
The North Lancashire examples of this species are very similar 
to the Yorkshire. There is, however, a slight calcareous thickening 
of the delicate spines in the margins of the vestibular apertures. 
Apparently this is caused by a secondary (chemical ?) deposit after (?)• 
the extinction of life in the Zoarium. Other spiniferous, or tubei-- 
cular species, are likewise affected by similar conditions, but only in 
certain localities. 
Localities: Yoredale ; Gleaston Castle, N. Lancas., Hurst, W. 
Yorkshire. 
28. Rhombopora similis ? Phillips' species. 
== ? Ceriopora similis, Phill. Palseozoic Fossils. 
In the Upper Shales of Scotland, and also in the Yoredale rocks 
of North Lancashire and North Yorkshire, there are examples of a 
species, that, for the present, I refer to Phillips' Cerio^oora similes. 
The shapes of the vestibules may be described as passing from 
