PROTOSPONGIA. 107 
forming the skeletal mesh are of a delicate character, the rays are circular 
in section and nearly of an even thickness throughout their length. It is 
probable that the spicules were originally rectangular, but in the type specimen 
the rays are now oblique, owing to the distortion produced by the compression 
of the rock matrix. There are five different series of squares in the Sponge-wall, 
the rays bounding the largest squares are 8 mm. in length by ‘2 mm. in thickness, 
whilst the rays forming the secondary and smaller squares are 4 mm., 2, 1, and 
*5 mm. in length respectively. The junction of the rays with each other is, in no 
case, distinctly shown; they can be traced nearly to the point of contact, and do 
not apparently overlap the squares in which they are situated. 
The typical example of this species, now in the British Museum, exhibits a 
fragment of the Sponge-wall on the surface of a slab of hard black shale. The 
original silica of the spicules has been replaced by iron-pyrites, and a delicate film 
of this mineral extends over the surface of the Sponge, and is probably a replace- 
ment of a siliceous dermal membrane, which served in part to hold the spicular 
mesh together. Not only is the spicular framework distorted, but in all the 
specimens I have seen it is partially broken up and many of the spicules absent or 
displaced. 
This species differs from Protospongia Hicksi in the much more slender 
character of the spicular mesh, which is very clearly shown in the figures of the 
two species on Plate I. 
Distribution.—Cambrian : Menevian Group, St. David’s, South Wales; Lower 
Lingula Beds, Tyddyngwladis, Upper Mawddach, North Wales. 
2. Prorosponeia Hioxst, Hinde sp. nov. PI. I, figs. 2, 2 a. 
1871. Prorosponata FenesTRATA, Hicks. Quart. Journ. Geol. Soe., vol. xxvii, 
p- 401, pl. xvi, fig. 20. 
1878. = — Brigger. Om paradoxidesskifrene ved Krek- 
ling, Nyt. Mag. f. Naturvidensk., 
vol. xxiv, p. 36, pl. vi, fig. 14. 
1880. _— — Ff, Roemer (in part).  Lethea palexozoica, 
Th. 1, p. 316, fig. 59 d. 
1880. — — Sollas. Quart. Journ. Geol. Soe., vol. xxxvi, 
p- 362, fig. 1. 
1884. — — Walcott. Pal. of the Eureka District, United 
States Geol. Surv., vol. viii, p. 10, 
pl. ix, figs. 5a, b. 
Sponge probably vasiform; the portions preserved indicate that the type 
specimen was at least 100 mm. in height by 75 mm. in width at thesummit. The 
