XV111. 



CONTENTS. 



Genus 15?. 

 Genus 153. 



Genus 154. 

 Genus 155. 



Genus 156. 

 Genus 157. 



Genus 158. 

 Genus 159. 

 Genus 160. 

 Genus 161. 

 Genus 162. 



Genus 163. 

 Genus 164. 



Genus 165. 



Genus 166. 

 Genus 167. 



Genus 168. 



Genus 169. 

 Genus 170. 

 Genus 171. 



Isodiscus Rattray, 188S . 

 Rattrayella De Toni, 1889 



Debya Rattr. olim, 1S88. 

 Aporodiscus Rattr., 1888. 



Cestodiscus Grev., 1865 . 

 Perithyra Ehr., 1854 



Heterostephania Ehr,, 1851 tubercles very small. 



Micropodiscus Grun., 1883 

 Tribe XXIII. Heliopeltete. 



ACTINOPTYCHUS Ehr., I 838 



Omphalopelta Ehr., 1844 valves cellular, with compartments alter- 

 nately furnished with spines. 



Symbolophora Ehr., 1844 valves with angular centre. 



Heliopelta Ehr., 1854 valves with margins furnished with spines. 



Halionyx Ehr., 1854 valves with rounded centre. 



Polymyxus J. W. Bailey, 1885 Valve undulated, without cellular 

 layer. 



Schuetlia De Toni, 1894 valve triangular, with excavated sides. 



Debya Pant., 1886 = internal valve of Aciinoptyckus, 



? Gyroptychus Ad. Schm., 1890 = a similar internal valve. 



Truania Pant., 1886 

 Actinodiscus Grev., 1863. 

 Anthodiscus Grove fr Sturt, 1887 . 

 Actinodictyon Pant., 1889 

 Lepidodiscus Witt., 18S5 . 

 Wittia Pant., 1889 



Tribe XXIV. Asterolampre/e . 



Liostephania Ehr., 1847 (Internal Valves?) 

 Gyroptychus Ad. Schm., 1890 (Internal Valves of 



Actmoptychus.) 

 Gladogramma Ehr., 1844. 

 Mastogonia Ehr., 1844 



Gyrodiscus Witt., 1885 



Group Asterolampra (E/ir., 1844) Char. Emend. 

 Actinogonium (internal valves of Asterolampra) 



Asterolampra Ehr., 1844 

 asteromphalus ehr., 1 844 



Spatangidium Breb., 1857 valve having a basilar ray, narrower, and 

 passing beyond the centre. 



Stelladiscus Rattray, 1890 



Asterodiscus Johns., 1852 central ray bifurcated. 



Rylandsia Grev., 1S61 

 Stictodiscus Grev., 1861 . 

 Arachnoidiscus Ehr., 1849 



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