PLATE II. 



Figs. 1, 1 a, 1 1. — Ischadites K(ENiGii, Murchison. 



Fig. 1. — The cast of a fairly complete specimen, showing the summit aperture and the vertical 

 furrows formed by the transverse rays of the spicules. Natural size. From Wenlock Limestone at 

 Wren's Nest, Dudley. The original specimen in the Woodwardian Museum at Cambridge. 



Fig. 1 a. — Compressed cast of a specimen, in which the spicular summit-plates have disappeared, 

 and the transverse rays beneath are shown. Natural size. From Wenlock Limestone, Dudley. The 

 original specimen in the British Museum (Natural History). 



Fig. i j, — Casts of two entire specimens, and fragments of four others, partially embedded in a 

 Blab of hard calcareous shale. The lozenge-shaped depressions are the casts of the spicular summit- 

 plates, and the casts of the transverse rays of the spicules can be seen in most of the depressions. 

 Natural size. From Lower Ludlow Eocks at Ludlow. Drawn from the type of the species, now in 

 the Museum of the Geological Society, Burlington House. 



Figs. 2, 2 a. — Ischadites Lindsteomi, Hinde. 



Fig. 2. — Cast of the basal portion of a specimen, partially embedded in matrix, showing the 

 concave base, the lozenge-shaped depressions of the spicular summit-plates, and the radial and 

 concentric lines formed by the transverse rays of the spicules. Natural size. Wenlock beds at 

 Malvern. The original specimen in the Natural History Museum, Oxford (Grindrod Collection). 



Fig. 2 a. — Cast of the upper portion of an individual, showing the central aperture and impres- 

 sions of the summit-plates. Natural size. Wenlock beds at Malvern. Original in the Natural 

 History Museum, Oxford (Grindrod Collection). 



Fig. 3. — Receptaculites Nepttjni ? Defrance. 



Cast of a portion of the under or outer surface of a specimen on a slab of limestone. The 

 margins of the spicular summit-plates are distinctly crenulated. Natural size. Wenlock Limestone, 

 Malvern. The original specimen in the Natural History Museum, Oxford (Grindrod Collection). 



Figs. 4, 4 a — 4 c. — Dictyophyton Danbyi, M'Coy, sp. 



Figs. 4, 4 a. — Casts of two specimens, partially embedded in an arenaceous matrix, showing in 

 high relief the vertical and transverse ridges formed by the spicules. Natural size. From Upper 

 Ludlow beds at Benson Knot and Brigsteer, Kendal. The original specimens in the Woodwardian 

 Museum at Cambridge. 



Fig. 4 b. — Casts of two specimens, in an arenaceous matrix, showing the impression of the spicular 

 structures in bas-relief. Natural size. From Lower Ludlow strata at Underbarrow, Westmoreland. 

 The original specimen in the Museum of the Geological Society, Burlington House. 



Fig. 4 c. — Portion of the surface of 4 a, enlarged five diameters, showing the larger and sub- 

 ordinate quadrate areas of the spicular mesh. 



Figs. 5, 5 a. — Astylospongia tncisolobata, F. Rosmer. 



Fig. 5. — The specimen seen from above, showing the canal- apertures. Natural size. From 

 Caradoc strata at Haverfordwest, South Wales. The original specimen in the Museum of the 

 Geological Survey, Jermyn Street. 



Fig. 5 a. — A transverse section of the same specimen, showing traces of the canals. The spicular 

 structure is not 



