PLATE XXXVIII. 



rig. 1. Pharetrospongia Strahani, SoUas. A fragment oL' tlie interior fibre, enlarged 

 seventy-two times, showing traces oi' the spicular structure. Drawn from a 

 transparent microscopic section of an entirely calcareous specimen. From the 

 Cambridge Green Sand oqi 



Figs. 2, 2 a, 2 b. Protosycon pundatum, Goldf . sp. Two specimens of average dimensions — 

 fig. 2 a is enlarged twice ; 2 b shows the cloaeal aperture at the summit. From 

 the Upper Jura at Streitberg 204 



Fig. 2 c. The same. A vertical median section of a specimen, natural size, showing the 

 thickness of the wall, and the eloacal tube filled with the matrix. 



Fig. 2 d. The same. A portion of the wall of 2 c, enlarged twenty-eight times, showing 

 sections of the spicules bounding the horizontal canals. Drawn from a trans- 

 parent microscopic section. 



Fig. 2 e. The same. A portion of 2 d, enlarged seventy-two times, showing sections of 

 three-raj'cd spicules. 



Figs. 3, 3 a, 3 b, 3 c. BactroneUa pusillum, Iliude. Three specimens of average dimensions. 

 Fig. 3 a is enlarged twice, the other figures are natural size. From the Upper 

 Jura, probably from Thurnau, Bavaria 205 



Fig. 3 d. The same. A segment of a transverse section, enlarged twenty-eight times, 

 showing traces of the canals in the marginal portion, and the general appearance 

 of the central part of the sponge. Drawn from a transparent microscopic 



section. 



Fig. 3 e. The same. A part of the margin of 3 rf. Enlarged seventy-two times. The dark 

 portions indicate the canals filled by the dark matrix, whilst the lighter parts are 

 sections of spicules. 



Fig. 3/. The same. A part of the dark central portion of the sponge, enlarged seventy-two 

 times, showing fragments of three-rayed spicules. 



Fig. Zg. The same. A part of a three-rayed spicule, enlarged two hundred times, showing 

 the spinous character of the rays. 



Figs. 4, 4 a. HapUstion fr actum, Hinde. Two detached fragments of the fibres, enlarged 

 fourteen times, showing the weathered-out spicules on the surface. Drawn by 

 reflected light. Frfim the Lower Carboniferous at Law Quarry, Dairy, Ayr- 

 shire ^07 



Figs. 5, 5 a, 5 b. Geodia ? antiqua, Hinde. Three detached trifid spiciil(!s, witli imperfect 

 shafts. Enlarged fourteen times. From the Lower Carboniferous at Law 

 Quarry, Dairy 208 



Fig. 3 c. The same. A portion of a curved accratc spicule. Enlarged fourteen times. 

 From Dairy. 



Figs. 5 d, e. The same. Two bifid spicules with imperfect shafts. Enlarged fourteen times. 

 The surface of 5 f shows in places small rhombohedral excavations. From Dairy. 



Figs. G, 6 a-6f. PachastreUa vetusta, Iliude. Detached spicules with four, and in one 



