KEY-TABLE. 121 



3. Nodular plates with an excavate margin met with in the following species : 



A. With flattened base, from 7 9 mm. in diameter, S. coronatus, PI. XXIV, 



fig. 2. 



,, ,, ,, 3 4 mm. 8. squamatus, PI. XXV, 



fig. 3. 



r,. With produced base, 8. pistilliferus, PI. XXV, fig. 5. 



4. Oblong or almost oblong plates having the characteristic ornament of 8. 

 Inilbiferu-8. These are the more distal marginals, or in some cases the ventro- 

 lateralia of this species. Generally the marginals are indented at the corners, and 

 their shape can be decided from the characteristic breast-plate form. 



Text-fig. 4, p. 113. Outer view of plate. 

 Text-fig. 31. Side view of plate. 



TEXT-FIG. 31. 



5. Irregularly rounded or polygonal plates with ocellate depressions having a 

 raised ridge. 



A. Without madreporiform markings on summit. 8. argus. PI. XXIX, 



fig. 8 a. 



B. With madreporiform markings on summit. S. ocellatus. Text- 



fig. 32. 



TEXT-FIG. 32. 



6. One specimen of Astropecten? sp. and Linckia sp. P respectively have also 

 been described, see pp. 90 and 100. 



UPPER GrREENSAND FORMS. 



The genus Comptonia appears to be characteristic of this horizon. The plates 

 are very similar in shape to those of Calliderma, except that they are more 

 rounded in profile. Unfortunately, no specimen at present known shows the 

 ornament of the marginalia. 



