PLATE XXV. 



Page 

 Fig. 1. Stauroneina compactum, Hinde. The lower portion of a specimen from the Gres 



vertj France ?, showing the front surface. Natural size 101 



Fig. 1 a. The same. Showing the outer surface of the same specimen. The canals in the 



lower portion arc concealed by the dermal layer. Natural size. 

 Fig. 1 b. The same. The fractured upper margin of the same, showing the thickness of the 



wall and traces of the canals. Natural size. 

 Fig. 1 c. The same. Portion of the dermal layer of the outer surface. Enlarged fifteen 



times. 

 Fig. 1 d. The same. A fragment of the interior spicular mesh. Enlarged sixty-two times. 



Drawn by means of the camera lucida. 

 Fig. 2. Sesti'odictyon convoluium,llinde. Natural size. From the Alpine Chalk ( = Upper 



Green Sand) at High Sentis, Canton Appenzell, Switzerland 102 



Fig. 2 a. The same. Fragments of the interior spicular mesh of fig. 2. Enlarged sixty-two 



times. The dark lines in the lower portion of the right-hand fragment represent 



canals which have been infilled with iron peroxide. 

 Fig. 3. Guettardia radians, Hinde. The lower portion of an imperfect specimen from 



Ci'ctaceous strata at Biarritz, France. Natui'al size 105 



Fig. 4. Trochobolus constrictus, Hinde. Natural size. From the Upper Jura at Randen, 



Switzerland 108 



Fig. 4 a. The same. Portion of a vertical median section of fig. 4, natural size, showing the 



tliickness of the wall. 

 Fig. 4 b. The same. Portion of the polished surface of 4 a, enlarged thirty times, showing 



the spicular mesh and the octahedi'al character of the nodes. The spicules have 



been replaced by calcite, and are consequently indistinct. 

 Fig. 5. Ventriculites convolutus, Ilinde. An imperfect specimen, preserved in chalk, 



showing both the outer and inner surfaces of the wall. Natural size. From 



the Upper Chalk at Broadstairs, Kent 110 



Fig. 5 a. The same. Portion of the outer surface of fig. 5, enlarged four times, showing the 



flattened ridges of the wall and the narrow interspaces. 



