§ 13. OXFORD CLAY. 501 



stone. From the pits near Faringdon* I have collected 

 hundreds of specimens in the course of a few hours ; and 

 the quarries near Calne, in Wiltshire, abound in echinites of 

 that beautiful species popularly called " Fairies' niglit-caps " 

 (Cida?^s, Lign. Ill, Jig. 3), which are often surrounded 

 by their spines, in as perfect a state as if they had just 

 sunk down into soft sand or mud ; detached spines of 

 these animals are found (Lign. Ill, jig. o,) in immense 

 numbers, f 



Many species of the bivalves called Trigonice y i of which 

 only one species, an inhabitant of the seas of Australia 

 and New Zealand, is known living, occur in these beds in 

 great perfection and abundance ; two species are here 

 figured (Lign. Ill) ; limestone casts of these shells are 

 very frequent in the Portland stone, and are generally ac- 

 companied with turritellce, terebraB, and other spiral univalves. 



13. Oxford Clay. — The Coral-rag rests upon a bed of 

 clay, in many places 300 feet thick, which is characterized 

 by the abundance and variety of its organic remains. Some 

 localities in Wiltshire are celebrated for the state of perfec- 

 tion in which many species of extinct cephalopoda occur. 

 At Christian Malford, near Chippenham, the cuttings for 

 the Great Western Railway, brought to light specimens of 

 the soft parts of the animals allied to the Sepiadae, or Cuttle- 

 fish, whose shells are so abundant in the argillaceous 



* Most of the heights around Faringdon are capped with Greensand, 

 overlying Coral-rag. Stanford pit, three miles south-east of Fariugdon, 

 contains : — 1. Uppermost, Coral-rag, 3^ feet ; 2. Limestone, with 

 immense numbers of shells, 4^ feet; 3. Sand, 3 feet; 4. Clay. These 

 beds abound in trigoniae, gervilliae, terebratulae, ostreae, helemnites, 

 and ammonites : in a slab of coarse sandy limestone, four feet square, 

 I counted above fifty gervilliae, and many trigoniae. Between "Watch - 

 field and Shrivenham the Coral-rag is seen in openings on the road- 

 side. See Medals of Creation, vol. ii. p. 923. 



f See Medals of Creation, vol. i. p. 343, for a particular account of 

 these fossils. X Ibid. p. 407. 



L L 2 



