PLATE XII. 



Pago 

 Fig. 1. Aulaxinia costata, Hinde. A silicified specimen in which the vertical canals have 



been infilled with silica and now appear as solid ridges. Natural size. From 



flint gravel at Stanway, Gloucestershire 60 



Fig. 1 a. The same. Portion of the outer sui-face of fig. 1, showing casts in flint of the 

 spicular skeleton. Enlarged eight times. 



Fig. 2. Trachysycon sulcatum, Hinde. A vertical median section of a silicified specimen, 

 showing sections of the funnel-shaped cloaca and traces of the canals. Two- 

 thirds the natural size. From the Upper Chalk of the South of England . . 63 



Fig. 2 a. The same. Portion of the outer surface of fig. 2, showing traces of the ridges and 

 broken spines. Natural size. 



Fig. 2 b. The same. Portion of the outer surface, enlarged sixteen times, showing traces of 

 spicules of the dermal layer. 



Fig. 3. Trachysycon nodosum,, Hinde. A vertical median section of a silicified specimen, 

 showing the interior of the cloaca and the course of the canals opening into it. 

 Natural size. From the Upper Green Sand at Warminster, Wiltshire ... 62 



Fig. 3 a. The same. Portion of the outer surface of the same specimen, showing the dome- 

 shaped elevations and the apertures of canals. Natural size. 



Fig- 3 b. The same. Showing the interior spicular skeleton, drawn from a polished surface. 

 Enlarged thirty-two times. 



