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 original silica of the spicules has been replaced by iron-pyrites, and a delicate film 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. Pkotospongia Hicksi, Hinde sp. nov. PI. I, figs. 2, 2 a. 



1871. Protospongia fenestrata, Sicks. Quart. Journ. Geol. Soc, vol. xxvii, 



p. 401, pi. xvi, fig. 20. 

 1878. — — Brogger. Om paradoxidesskifrene ved Krek- 



ling, Nyt. Mag. f. Naturvidensk., 

 vol. xxiv, p. 36, pi. vi, fig. 14. 

 1880. — — F. Boemer (in part). Lethsea palseozoica, 



Th. 1, p. 316, fig. 59 b. 

 1880. — — Sollas. Quart. Journ. Geol. Soc, vol. xxxvi, 



p. 362, fig. 1. 

 1884. — — Walcott. Pal. of the Eureka District, United 



States Geol. Surv., vol. viii, p. 10, 

 pi. ix, figs. 5 a, 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 the summit. The 



