Poryzoa.| LOWER PALEOZOIC RADIATA. AT 
Position and Locality—Very common in the slates of Mynydd, Fron Frys; five miles W. of Chirk, 
Glyn Ceiriog ; Llansantfraid, Glyn Ceiriog, Denbighshire; Llanfyllin, Montgomeryshire ; Blain y Cwn, W. 
of Nantyre, Glyn Ceiriog; Cyrn y Brain, W. of Wrexham, Denbighshire ; Coniston limestone of Coniston, 
Lancashire; limestone of Mathyrafal, S. of Meifod, Montgomeryshire; schists, N. end of Pen y Craig, 
above Glyn Llangynyw, Montgomeryshire. 
Explanation of Figwres—P\. 1. C. fig. 16. Portion of one of the thin undulating foliaceous expansions, 
shewing the thin wrinkled central plate or axis, with the cells sticking on in some places; natural size, 
from the slates of Llansantfraid—Fig. 16a. Portion of ditto, magnified six diameters, shewing the cast 
of the cells, each with its terminal aperture, and attached by its posterior narrow end to the thin undulated 
mesial plate —Fig. 164. Cast of portion of surface magnified twelve diameters, shewing the round apertures 
of the cells, in the middle of the rhomboidal outer wall, with the granular impressions of the interstitial 
pitting ; from Coniston. 
Pritopicrya (Stictopora) FucOIDES (A/*Coy). PI. 1. C. fig. 14. 
Ref.—MCoy, Ann. Nat. Hist. 2nd Series, Vol. VI. p. 288. 
Sp. Ch.—Corallum forming very thin, flat, sub-membranous, foliaceous, linear expansions, averaging one 
and half to two lines wide, frequently dichotomising at an acute angle; branches very rarely, but occa- 
sionally anastomosing ; cells extremely small (eight in the space of one line) about eighteen rows in the 
width of the frond, very close, quincuncially arranged, without perceptible linear disposition ; internal axis 
smooth, nearly membranous. 
The extreme minuteness, number, and close disposition of the cells easily distinguish this species from 
the P. acuta, or costulata, and often give a resemblance to some fucoid. 
Position and Locality—Not uncommon in the schists of Llansantfraid, Glyn Ceiriog, Denbighshire ; 
schists of Gelli Grin, Bala, Merionethshire ; and schists of Corwen, Merionethshire. 
Explanation of Figures —PI\. 1. ©. fig. 14, From the schists of Llansantfraid—Fig. 14. Portion 
of ditto magnified twelve diameters. 
PTILODICTYA LANCEOLATA (Gold. Sp.) 
Ref. and Syn—Flustra lanceolata (Gold.) Pet. Germ. t. 37. f. 2. Sil. Syst. t. 15. f. 11. Ptilodictya 
sublanceolata (D’Orb.) Prod. p. 44. 
Sp. Ch.—Corallum forming a simple compressed, slightly curved, nearly parallel-sided or linear expan- 
sion, from an inch long, with a width of one and half lines, to upwards of five inches long with a breadth 
of five lines; two broad faces slightly convex, but specimens often splitting parallel with the flat central 
axis; edges acute ;- both surfaces marked with longitudinal, parallel, very slender ridges (averaging nine in 
one line), eight or ten in the middle, closer, and more prominent than the rest, crossed by transverse promi- 
nent strize (about six in one line) which are nearly horizontal for a narrow space in the middle, but 
incline upwards and outwards at the sides, at an angle of about 70°, the included oblong and rhomboidal 
spaces containing each an elongate ovate cell, placed longitudinally to form a few small longitudinal rows 
in the middle, and diagonally at the sides to form rows extending obliquely upwards and outwards; axis 
thin marked along the middle with strong arched undulations, the convexity towards the apex; the margins 
nearly smooth or marked with obscure longitudinal and oblique striz. 
I have clearly ascertained the existence of a central axis as above described in this species, and most 
specimens are actually split parallel to this axis, thin irregular films of which usually adhere to the flat 
surface; by examining the matrix towards the edge, the two rows of cells, one above and one below this 
central plate, may usually be found. 
Position and Locality—Not uncommon in the limestone of Clungunford, Shropshire ; limestone of Pen 
y Craig, above Glyn, Llangynyw, Montgomeryshire ; Aymestry limestone of Aymestry, Herefordshire. 
