COELENTERA — CORALS. 



55 



Durham ; CyathopTiyllum, largely represented in the Table- Gallery X. 

 case, and by some polished slabs of C. regium from Bristol ; "Wall-ease 

 Clisiophyllum and Aspidophyllum, which end the series. 

 Henceforward these Tetracoralla disappear from the rocks ; 

 but the living Astraeid coral, Moseleya, has \^hen young a 

 four-rayed symmetry which indicates relationship to the 

 Cyathophyllidae. We may therefore suppose that the latter 

 forms were the ancestors of the Astraeidae. 



N"either Permian nor Triassic corals are represented 

 in the British series, but there are shown specimens from the Wall-ease 

 Zechstein, as well as the Klipstein collection from the Triassic ^' 

 beds of St. Oassian in the Tyrol. 



The next coral fauna represented in the British islands is 

 that of the Lias, the earliest of the Jurassic corals. This Table-ease 



Fig. 24. — Zoantharian Corals of Bajocian Age, from the Inferior Oolite of 

 England, a, Latomseandrxa'' Flemingi. b, Montlivaltia trochoides. 

 (From Prestwich's " Geology.") 



shows a great change ; all the Palaeozoic genera have given 

 place to normal representatives of existing families and 

 genera, such as Isastraea and Montlivaltia (Figs. 24: b, 25 h). 

 The collections from the Inferior Oolite are richer, and the Table-ease 

 representatives of modern genera are increased by Fungians, ^• 

 such as TJiamnastraea, and also by a doubtful species (Fig. 24 a) 

 representing the confluent Astraeids, in which the polyps 

 and calyces are incompletely separated as in the Brain- 

 coral. In the rocks of Bathonian age are many corals of 

 similar type, the chief reef-builder being Calamop)]iylla 

 radiata. In the Corallian rocks true reefs are formed of Table-ease 

 Thecosmilia, Thamnastraea, and Isastraea, of which large 2- 

 specimens are shown (Fig. 25). The structure of all these Wall-ease 

 Jurassic corals, as of the succeeding Cretaceous and Tertiary ^• 

 genera, can be gathered from the diagrams placed in the 

 Table-cases. An interesting series is that of Isastraea oUonga, 



