Potyzoa. | LOWER PALAEOZOIC RADIATA. 45 
BERENICEA HETEROGYRA (M‘Coy). Pl. 1. C. fig. 17. 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VI. p. 286. 
Sp. Ch.—Parasitic, often on Orthoceratites, covering spaces of upwards of two inches square; cells 
disposed in circular groups of irregularly radiating, or divaricating fan-shaped lines, ten or eleven occupying 
the space of one line (measured across their length), and about three in the same space in the direction of 
their length; each cell slightly more than the third of a line long, very narrow, fusiform, about four times 
longer than wide, and separated by a space, varying from their greatest width to less than one half their 
width, or nearly in contact; upper convex surface of each cell with four or five large tubercles when 
well preserved. 
This remarkable species is almost invisible to the naked eye, but occurs forming patches of considerable 
size; the small size of the cells, and their very elongate slender form, distinguish it from the B. irregu- 
laris of Lonsdale. 
Position and Locality—Coniston limestone of Coniston Water-Head, Lancashire. 
Explanation of Figures.—P|. 1. C. fig. 17. From the Coniston limestone of Coniston, natural size, 
parasitic on an Orthoceratite—Fig. 17a. Portion of Do. magnified six diameters—Fig. 175. A few of 
the cells of Do. magnified fourteen diameters, shewing the terminal aperture and the granulation on the 
outer wall. 
Genus. PTILODICTYA (Lonsd.) 1839 as here redefined. 
< Stictopora (Hall, 1847). 
Gen. Char.—Corallum thin, calcareous, foliaceous, or branching dichotomously, branches sometimes 
coalescing ; a thin laminar, flattened, concentrically wrinkled central axis, set with oblique short subtubular 
or ovate cells on both sides, with prominent oval mouths nearly as large as the cells within; branches 
often flattened, with the margin solid, sharp-edged, striated and without cells; the boundary ridges of the 
cells square or rhomboidal. 
Mr Hall believes that the cells are only simply tubular, not utricular or contracted at base as in 
Cellepora, Membranipora, &e. 1 have, however, clearly determined them in our British examples to be 
so; yet I think the genus is undoubtedly distinct from both those recent genera—from the first by the 
cells not being piled, and from the second by the cells being calcified in every part, instead of the anterior 
wall being mere membrane. I have ascertained that the flat surface of most specimens of Ptilodictya 
is owing to a splitting of the coral parallel with the flat central axis, which I have traced in several 
specimens of Lonsdale’s type species, presenting the exact appearance of that in the Stictopora of Hall. 
I also find a perfect generic identity in the form, structure, and disposition of the cells; the latter genus 
must therefore be united to the former under the old name, which, however, is very inappropriate to all 
but the first described species. Mr Hall’s name might perhaps be used as a subgenus for the polymorphous 
species. 
Pritopicrya (Stictopora) acuta (Hall. Sp.) 
Syn. and Ref.—Stictopora? acuta (Hal. Pal. N. Y. t. 26. f. 3.) 
Sp. Ch.—Corallum forming flat, thin, linear expansions, about one and half lines wide ; dichotomously 
branching at an angle of about 50°, the branches almost as wide as the main stem; from seven to ten 
alternating longitudinal rows of small ovate cells, apparently arranged in lines extending from the centre 
very obliquely upwards and outwards, or abruptly curving outwards at the sides ; lateral edges with a narrow, 
sharp, apparently solid margin, smooth or with oblique striee, corresponding to the direction of the lines of 
cells; mouths of the cells in each row four in one line. 
