74 



LOWER LIAS. 



Below the Ammonitiferous nodules (5 of the section) other bands of clay and marl 

 (6 to 14) succeed. In one of these (9) are thin layers of Crinoidal limestone, on the 

 surface of which magnificent specimens of Extracrinus Briareus, Mill., are found, with 

 their plant-like arms laid out in all directions, and generally coated with sulphuret of iron. 

 The remarkable Liassic Dinosaurian SceUdosaurus Harrisonii, Ow., so fully figured and 

 described in the Palseontographical Society's volume for 1859 was discovered some years 

 ago by Mr. Samuel Clarke, of Charmouth, in the dark shales of bed No. 8, above the 

 mudstones. 



Fossils of the Zone of Ammonites obtusus. 



Scelidosaurus Harrisonii, Owen. 

 Ammonites obtusus, Sow. 



— Brookii, Sow. 



— stellaris. Sow. 



— planicosta, Sow. 



— Dudressieri, d'Orb. 



— Sauzeanus, d'Orb. 



Ammonites Sraitliii, Sow. 



— Birchii, Sow. 

 Nautilus striatus. Sow. 

 Belemnites acutus, Mill. 

 Pleurotomaria Anglica, Sow. 

 Inoceramus, n. sp. 

 Extracrinus Briareus, Mill. 



5. The Zone of Ammonites oxynotus. 



Synonyms. — " Oxynoten-Schichte," Fraas, 'Wiirttemb. naturw. Jahreshefte,' 1847, 

 p. 206. " Oxynotenlager,'' Quenstedt, 'der Jura,' p. 293, 1858. "Die Schichten des 

 Ammonites owynottis" Oppel, 'die Juraformation,' p. 54, 1856. " Oxynotus-bed," 

 Wright, ' Quart. Journ. Geol. Soc.,' vol. xiv, p. 25, 1858. " Zone of Ammonites oxynotus" 

 Wright, ' Quart. Jour. Geol. Soc.,' 1860, vol. xvi, p. 406. 



In Gloucestershire this zone consists of beds of dark clays, which often contain 

 much sulphuret or peroxide of iron, all the fossils found in the clay being either highly 

 pyritic or charged with the peroxide of that metal. This bed was exposed in the cuttings 

 of the Bristol and Birmingham, and Great Western Railways, at Lansdown, near Chel- 

 tenham, and in excavating the new docks at Gloucester ; I have likewise collected its 

 characteristic fossils at other localities in the Vale of Gloucester. 



In Dorsetshire a variety of Ammonites oxynotus, Quenst., is found in a thin bed of 

 dark, pyritic marl between Charmouth and Lyme Regis, near Black Venn. It is here 

 collected with other species, which properly belong to a higher bed ; the falling down of 

 the upper marl, by the decay of the bank, makes it difficult to separate the beds. 



At Robin Hood's Bay, on the Yorkshire coast, the relative position of this zone to the 

 beds with Ammonites obtusus, Sow., below, and Ammoyiites raricostatus, Ziet., above, are 

 seen in the cliff near the point where the road leads up to the Alum-works. At this 

 locality the Am. oxynotus bed is about 20 feet above the clays with Am. obtusus. 



The form of Ammonites oxynotus, Quenst., collected near Cheltenham, exactly resembles 

 the original type of this Ammonite found in Wiirtemberg. I possess a series of this 



