120 



FOSSIL ASTEROIDEA. 



3. Spine-pits fine. 8. Boysi. Text-fig. 

 27, (a) outer view of marginal, (b) 

 interior view of marginal. 



Text-fig. 27. 



B. Without spine-pits. 



/ 



/ 



; 



Text-fig. 29. 



Text-fig. 28. 



1. Maximum size about 7 mm. S. coro- 



natus. Text-fig. 28. 



2. Maximum size about 25 mm. 8. 



squamatus. 



3. Maximum size about 25 mm. 8. 



pistilliferus. Text-fig. 29. 

 N.B. — It is impossible to distinguish 

 isolated marginalia of these two species. 

 Compare V, 3 (p. 121). 



V. — The collector may also come into possession of the following plates : 



1. Large triangular plates liaving the characteristic ornament of Metopaster. 

 These are the ultimate supero-marginalia which characterise the genus. See e. g. 

 PI. XVI, fig. 2 a. 



2. Large hemispherical plates with a flattened base. These are met with in 

 the following species : 



a. With spine-pits. 



Stauranderaster bulbiferus, S. Boysi, 

 and ? S. bipundatus. These are 

 distinguished from one another 

 by their spine-pits, which are of the 

 same character as those met Avith 

 in the marginalia. Text-fig. 30 = 

 a primary inter- radial of S. bulbi- 

 ferus. 



b. Without spine-pits. 



Pycinaster senonensis, distinguished by 

 the smooth surface, PI. XXIX, 

 fig. 6. 



Arthraster Bixoni, distinguished by the 

 rugose surface, PL XXIX, fig. 11. 



Text-fig. 30. 



