KEY-TABLE. 



119 



III. — Marginals generally wedge-shaped, high, spine-pits very shallow or absent. 

 Pedicellariae when present with five valves round a deep central 

 depression. Pycinaster. 



(A) 



(B) 



Plates of maximum height, 10 

 mm. P. angustatus. See PI. 

 IX, fig. 1 a, 



Plates of maximum height, 20 

 mm., P -shaped in profile. P. 

 senonensis. Text-fig. 23, (a) 

 outer view of marginal, (b) 

 interior view of marginal, (c) 

 side view. 



Text-fig. 23. 



3. Plates very thick, often oblong, 

 not wedge-shaped. P. crassus. 

 PI. XXIX, fig. 3, exterior view 

 of marginal. Text-fig. 24, side 

 view of marginal. 



Text-fig. 24. 



IV. — Marginal plates breast-plate-shaped. Staitranderaster (see p. 125). 

 a. With spine-pits. 





1. Spine-pits fairly coarse. S.bul- 



bifertis (commonly occurring). 

 Text-fig. 25. 



2. Spine-pits medium. 8. bipunc- 



tatus (only one specimen 

 known). Text-fig. 26. 



Text-fig. 25. 



Text-fig. 26. 



