MANUAL OF NATURAL HISTORY. 563 



Crenatula, Corbula, Pholadomya, and Nucula, be- 

 sides an Area, Pinna, Oardium, and Pecten, in the 

 higher beds ; with Posidonia, and a large Pla- 

 giostoma. The brachiopodous genus, Spirifer, ap- 

 pears in the Lias for the last time ; and Leptcena 

 occurs in the neighbourhood of Ilminster. Of Echi- 

 noderms, we find the slender-armed Ophiuri, and 

 elegant plant-like Crinoidea, chiefly belonging to 

 the genus Pentacrinus. The Cidaris, a genus of 

 Sea-Urchins (Echinidce), is also found. 



The plants of the Lias consist of Zosterites, a 

 monocotyledonous genus ; several Coniferce ; Nill- 

 sonia, and Zamia, of the cycadaceous family ; the 

 Tongue-fern (Glossopteris) ; the Wreath-fern (Tceni- 

 opteris) ; and the Lattice-fern (Clathropteris). 



III. THE OOLITE, OR JURA GROUP. 



The Oolite comprises a series of marine strata of 

 enormous extent, consisting of limestones, sand- 

 stones, and clays, with calcareous grits, replete with 

 corals, shells, fish, reptiles, terrestrial plants, and 

 species of mammalia. It occurs in England, com- 

 mencing at the isle of Portland, follows a winding 

 course through several counties, and ends at the 

 sea, near Scarborough. On the Continent, it is 

 developed in Normandy, traverses France, forms 

 the mass of the Jura, ancj part of the Alps ; and is 

 found also in Germany, Poland, Portugal, and Spain. 



The Bavarian Jura is celebrated for the litho- 

 graphic stone of Solenhofen ; in the lower division 

 of the Oolites the Bath stone occurs so extensively 



