342 CRETACEOUS ECHINODERMATA. 
4. Holaster cor-avium, Lamarck? (Tab. XXIV. fig.7; figs. 8 & I— 
the anal plates.) 
The curious species of Holaster, figured as above, is referred with doubt to the 
Ananchytes cor-avium of Lamarck, with the brief notices of which it agrees very 
well. Unfortunately there is no good figure of the Lamarckian species for 
comparison. 
From the white chalk of Sussex. 
Genus MicrasteEr, Agassiz. 
1. Micraster gibbus (Spatangus), Lamarck. (Tab. XXIV. figs. 5, 6.) 
This is not the Spatangus gibbus of Goldfuss. The Micraster gibbus of Agassiz 
and Desor is said, in the ‘ Catalogue Raisonné des Echinides,’ to have very 
slightly impressed ambulacra. The species here figured, however, has the 
avenues rather strongly impressed. It agrees so well with the figures in the 
‘Encyclopédie Méthodique’ (pl. 156. figs. 4-6), referred to by Lamarck as re- 
presenting his Spatangus gibbus, that I do not hesitate to identify it with that 
species. 
Chalk of Sussex. 
2. Micraster cor-bovis, sp. nov. E.F. (Tab. XXIV. figs. 3, 4.) 
The body of this fine and large Micraster is ovate and slightly cordate, broad- 
est in the region of the antero-lateral ambulacra. The posterior end is obtusely 
subtruncated. The dorsal surface is depressed and but slightly elevated in the 
anterior region above the rest of its surface. The ovarian circle is placed nearer 
the anterior than the posterior end. The frontal groove is shallow. The lateral 
ambulacra are placed in gentle depressions. The postero-lateral ambulacra are 
very short, and little more than half the length of the antero-laterals. There 
are about thirty pair of pores in each row in the latter, and about seventeen in 
each row in the former. The larger tubercles of the dorsal plates are much 
scattered and minute in proportion to the size of the shell. The interstices 
are minutely granulated. The areolated tubercles of the ventral surface are also 
proportionally small. The post-oral spinous space is triangularly lanceolate. 
Length 3 inches ; breadth 2 inches 74ths ; height 1 inch 7°yths. 
Chalk of Sussex. 
