PLATE III. 



Figs. 1, 1 a, 1 b. — Pleotodbema scitultjm, Hinde. 



Fig. 1. — A portion of the wall of the Sponge, showing the disposition of the 

 spicular-mesh, for the most part represented merely by negative casts. Natural 

 size. From Upper Ludlow strata in the Pentland Hills. The original specimen 

 in the Collection of the Geological Survey of Scotland, Edinburgh. 



Fig. 1 a. — A portion of the same specimen, showing the fasciculate arrange- 

 ment of the vertical rays, and the single disposition of the transverse rays of the 

 mesh-spicules. The silica of the spicules is, in part, preserved. Magnified five 

 diameters. 



Fig. 1 b. — Another portion of the specimen, similarly enlarged, showing casts 

 of cruciform-spicules. In the larger spicule, to the right of the figure, a fifth ray 

 is indicated. 



Figs. 2, 2 a, 2 b. — Phormosella ovata, Hinde, nov. sp. 



Fig. 2. — Impressions of nine individuals on a slab of arenaceous rock. Natural 

 size. From Ludlow strata at Mocktree, Shropshire. The original specimen in the 

 Museum of the Geological Survey, Jermyn Street. 



Fig. 2 a. — A single Sponge, magnified two diameters. 



Fig. 2 b. — A portion of the surface of a specimen showing the disposition of 

 the cruciform-spicules in the Sponge-wall. Enlarged five diameters. 



Figs. 3, 3 a—f. — Amphispongia oblonga, Salter. 



Fig. 3. — Casts of nine individuals, closely associated together on a slab of 

 arenaceous rock. Natural size. From Upper Ludlow strata at Wetherlawlinn, 

 Pentland Hills, near Edinburgh. The original specimen in the British Museum 

 (Natural History). 



Fig. 3 a. — A single Sponge with indications of an axial hollow in its lower 

 portion. Natural size. 



Fig. 3 b. — A portion of the upper surface of a specimen, showing the regular 

 arrangement of the spicules, now represented by negative casts. Enlarged ten 

 diameters. 



Figs. 3 c, 3 d. — Casts of two detached spicules, forming the upper portion of 

 the Sponge. Enlarged twenty diameters. 



Figs. 3 e, 3/. — Casts of two detached conical spicules, forming the basal portion 

 of the Spouge. Enlarged ten diameters. 



