MESOZOIC TIME — TRIASSIC AND JURASSIC. 



777 



Stonesfield slate, chiefly near Woodstock, where have been found over 80 

 species of Ferns, nearly 20 of Conifers, and 40 of Cycads. The Middle and 

 Upper Oolyte have afforded about 16 other species. The Conifers are of 

 the genera Taxites, Tlmyites, Ciqyressites, Arcmcarites, — names which express 

 their modern relations. There were also Endogens of the Arum and Pan- 

 danus families ; but no Angiosperms or Palms. The " dirt-bed " at the base 

 of the Purbeck has afforded stumps of Cycads (Fig. 1268), including three 

 species of Mantellia, one of which is shown in Fig. 1269. There is also a 

 species of Pine {Pinites), besides a few other plaiats. 



Invertebrates. — Siliceous Sponges, both the Hexactinellid (Fig. 

 1270) and Lithistid kinds, were very common in the Middle and Upper 

 Oolyte, and so-called sponge-beds occur in the European Oolyte at different 

 levels. 



Polyp-corals were of many kinds, of the modern Hexacoralla type (hav- 

 ing the rays a multiple of 6). The Corals flourished like the species of 



1272. 



1270. 



1271. 



WMWmM 







Sponge, of the Oolyte. - 



•Fig. 1270, Tremadictyon reticulatum. Polyp-corals, of the Oolyte. - 

 Uvaltia caryophyhata ; 1272, Isastrsea oblonga. D'Orhigny. 



-Fig. 1271, Mont- 



modern coral reefs (1) in the pure ocean waters, and (2) many too in the 

 shallow waters of the ocean's borders, as about modern coral reefs. For 

 (1) the limestones make several alternations with the sediments, clays, 

 and sand-beds of the sea margins ; and (2) only the purer limestones contain 

 the corals. They abound in England in some beds of the Lias, in both 

 sections of the Lower Oolyte, the Inferior and the Great Oolyte, in the Corallian 

 of the Middle Oolyte, but are absent from the Kellaway beds or Oxford clay 

 of the Middle, and from all of the Upper Oolyte beds in England, excepting 

 a single species, Isastrcea oblonga (Fig. 1272), in the Portland limestone. 

 The reef species of the Oolyte may have flourished at greater depths than 

 those of existing reefs, but appear not to have been, in general, abyssal 

 species. 



The most of the species of the Lias are of the genera Montlivaltia (M. caryophyllata, 

 Pig. 1271, from the Bath Oolyte), Thecosmilia, Astrocoenia, Isastrcea; and excepting 

 Astroccenia these, witli Thamnastrcea, are the most prominent genera in the Lower Oolyte. 



