118 



FOSSIL ASTEROIDEA. 



2. No spine-pits on central raised area. 



(A) (B) 



-i 



Text-fig. 19. 



a. Kugosities present on greater portion of surface 

 of supero-marginalia. If. rugaius. Text-fig. 

 19, (a) supero-marginal, (b) infero-inarginal. 



6. Rugosities confined to inner edge of supero- 

 marginalia or absent; outer portion of plate 

 tumid, a. Plates oblong. If. uncatus. Test- 

 fig. 20, (a) supero-marginal, (b) iufero-mar- 

 giual. /3. Plates square, if. qiiadratus. 



c. No rugosities present ou the supero-marginalia 

 which are not tumid on their outer portion. 

 M. compacfus. See PI. XXVI, fig. 3 b. 



Text-fig. 20. 

 N.B. — Tlie infero-marginalia of the above species are diflicult to distinguish except by 

 their dimensions. The reader is advised to refer to the detailed description for these. 



c. Marginalia Avitli a distinct ridge wliicli lias granular elevations along 

 its base. Jiihraster. 



(A) (B) 



1. Upper surface of ridge smooth. A. Bizoni. 



Text-fig. 21, (a) outer view of marginal, (b) 

 side view of marginal. 



2. Upper surface of ridge with spine-pits. A. cris- 



tatiis. See PI. XXIX, fig. 10. 



Text-fig. 21. 



II. — Plates either hexagonal or rounded ; very thick. Spine-pits form a distinct, 

 fine honeycomb marking. Hadranderaster (see p. 12-5). 



(A) 



(B) 



There is only one species. H. abhreviatus. Text- 

 fig. 22, (a) outer view of marginal, (b) side 

 view of marginal. 



Text-fiq. 22. 



