PLATE XIII. 
Figs. 1—1¢.—Mertonetia ovata, Sollas, sp. (Page 207.) 
Figs. 1, 1 a.—The type-forms of the species. Natural size. Inferior Oolite, Hwmphresianus-zone, 
at Dundry Hill, near Bristol. (Collection Rev. G. F. Whidborne.) 
Fig. 14.—A portion of a vertical median section of one of the specimens, showing the spicular 
structure, now replaced by calcite. Enlarged 50 diameters. 
Fig. 1e.—A portion of the surface of 1a, showing the weathered-out spicular nodes. Enlarged 
50 diameters. 
Figs. 2, 2@.—CYLINDROPHYMA MILLEPORATUM, Goldfuss, sp. (Page 208.) 
Detached siliceous spicules of this species. Enlarged 50 diameters. From the Upper White Jura 
of Beuren, Germany. Figured for comparison with the preceding. 
Figs. 3, 4.—PacuasTRELLA ANTIQUA, Moore, sp. (Page 208.) 
Fig. 3.—Detached caltrop spicules of this species. Enlarged 20 diameters. From chert in the 
Portland Beds, Isle of Portland. Museum of the Geological Survey, Jermyn Street. 
Fig. 4.—A section of Lower Lias Limestone, showing spicules of this species intermingled with 
others, all of them now replaced by calcite. Enlarged 20 diameters. Lower Lias, Shepton Mallet, 
Somersetshire. 
Fig. 5.—Geovires, sp. (a). (Page 209.) 
An imperfect trifid spicule. Enlarged 20 diameters. From the cherty bands in the Portland 
Limestone, Isle of Portland. 
Fig. 5a.—Guopirss, sp. (6). (Page 210.) 
An imperfect trifid and a simple acerate spicule, probably belonging to the same species. Inferior 
Oolite, Parkinsoni-zone, at Burton Bradstock. 
Figs. 6, 6a.—Sponci~ta PURBECKENSIS, Young. (Page 212.) 
Fig. 6.—A section of chert filled with the spicules of this species. Enlarged 50 diameters. From 
the Purbeck Limestones at Stare Cove, Lulworth, Dorsetshire. 
Fig. 6a.—Longitudinal, oblique, and transverse sections of some of the spicules. Enlarged 
100 diameters. 
Figs. 7—7 f£—Ruaxetta peRFoRATA, Hinde, (Page 210.) 
Fig. 7.—An imperfect specimen, partially weathered out of a slab of rock. Natural size. From 
the Lower Calcareous Grit, Scarborough, Yorkshire. York Museum. 
Fig. 7 a.—A fragment of another specimen, showing the slit-like apertures in the wall. Natural size. 
Fig. 7b.—A transverse section of the same piece, showing the disposition of the wall-lamine. 
Natural size. 
Fig. 7¢.—A thin section of a fragment of the wall, showing its composition of globate spicules. 
Enlarged 20 diameters. 
Fig. 7 d.—Some of the detached spicules, showing variations in form and size. 
Fig. 7 e.—A single spicule, mounted in glycerine, showing traces of its component rods. Enlarged 
200 diameters. 
Fig. 7f—Anotiher speule, similarly enlarged, showing the surface structure. 
