TAUNA OF THE LIAS. 419 



in fossil shells. In Yorkshire a similar division of the lias 

 has been observed.* 



FAUNA or THE I/IAS. Corals are rarely found in this 

 stage, but in "Warwickshire some beautiful masses of Astrea 

 have been discovered. The bed of the liasic sea was strewed 

 with numerous plant-like Crinoideans belonging to the genus 

 Pentacrinus ; many fine specimens of P. briareus, have been 

 obtained from Lyme-Regis. A few slender armed Ophiura 

 have been found in the same rich locality. Larger species 

 are preserved in the shales of Gloucestershire, and in the 

 marlstone of Yorkshire. The genus Cidaris is likewise 

 found in the Vale of Gloucester. The Conchiferous Mollusca 

 were very abundant in many localities; numerous indivi- 

 duals of the genera Gryphoea, Cardinia, Lima, Avicula, and 

 Hippopodium, are found in the lower lias shales. Crenatula, 



FIG. 288. Area Buckmanni. 



Corbula, PJioladomya, and Nucula, occur in a higher zone, 

 and a species of Area (fig. 288) is found in the upper beds 

 of the lower lias shales. The plate (fig. 289) exhibits some 

 of the most common and characteristic genera of liasic shells. 

 The Marlstone contains many conchifers that are special 

 to it, as Qryphcea gigantea, Pinna liar tmanni, Avicula cygnipes, 



* For full particulars relating to the lithological character of these beds, the 

 student is referred to Sir R. Murchison's Geology of Cheltenham, Second 

 Edition; Professor John Phillips' Geology of Yorkshire; and the Rev. P. B. 

 Brodie's Fossil Insects. 



EK'2 



