778 



HISTORICAL GEOLOGY. 



The Isastroea, Thecosmilia, and Thamnastrcea corals are massive kinds. Etheridge's 

 tables for British fossils in 1885 give the number of Jurassic species, in all, 236, and of 

 these the genera mentioned contain : — 



Total 



Astrocoenia 14 



Isastrsea 24 



Montlivaltia 44 



Thecosmilia 21 



Thamnastraea 27 



Lias Lower Oolyte Middle Oolyte Upper Oolyte 

 14 



10 18 4 1 



25 18 1 



14 6 1 



21 23 3 



EcMnoderms were in profusion, as in existing coral seas. Crinoids were 

 numerous of the genera Pentacrinus, Apiocrinus, and others. Pentacrinus 

 (Extracrinus) Briareus (Fig. 1278) is one of the common and most re- 

 markable of the species in the Lias ; a bed in the Lower Lias is largely 



1273-1278. 



1273 



1278 



1277 



EoHiNODEKMS. — Fig. 1273, Apiocrinus Roissyanus (x J), Oolyte, the middle part of the stem omitted; 1274, 

 Saccosoma pectinata, Oxfordian ; 1275, Pseudodiadema seriale ; 1276, Cidaris Blumenbachii ; 1277, spine of the 

 last ; 1278, Pentacrinus (Extracrinus) Briareus. 



