213 



Cephalopoda. 



Ammonites Jason, Reinecke. 



Guillelmi, Sow. 



Coniptoni, Pratt. 



Lonsdalii, Pratt. 



Bdglitii, Pratt. 



Eeginaldi, Mor. 



Ammonites fluctuosus, Pratt. 



" cordatus, Sow. 



" modiolaris, Llhwyd. 



Belemnites Puzosianus, iVOrh. 



" hastatus, d'lllain. 



Acanthoteuthis antiquus, Pearce. 



Gasteropoda. 



Turritella mxmcata, Sow. 

 Alalia composita, Sow. 



Alaria bispinosa, Phil. 

 " triBda, Phil. 



CONCHIPEEA. 



Gryplisea dilatata, Sow. 

 Ostrea gregaria, Sow. 

 Avicula inaequivalvis, Soiu. 

 II ovalis, Phil. 



Modiola bipartita, Sow. 

 Plioladomya deltoidea, Soiv. 

 Nucula PhiHipsii, Mor. and Lye. 

 II elliptica, Phil. 



The Zone of Ammonites perarmatus, — or lower Calcareous Grit, 

 is the equivalent of the "marnes ferruginenses oolithiques a 

 Am. cordatus, Am. perarmatus, Am, oculatus, &c.," of M. Maetist. 

 This formation is by most English geologists *^ considered a 

 subordinate member of the Coral Rag, though (-.outaiuing some 

 fossils peculiar to itself, and being principally an arenaceous 

 instead of a calcareous rock." With some contiaental authors it 

 is the upper memher of the Oxfordian stage, as having greater 

 palseontological affinities with the other divisions of this group 

 than with the coralline Oolite which rests upon it. 



It consists of a series of soft, variegated, siliceous sands, 

 alternating with calcareous grits, and bands of siliceous Lime- 

 stone, with fossils. The beds of Calcareous Grit are very 

 irregular, and frequently present the phenomena of obKque 

 lamination or current-bedding.'^ It varies in thickness from 

 20 to 80 feet. In the bands of calcareous sandstone, fossils are 

 plentiful, though generally fragmentary. This zone is well 

 developed near Calne, Wilts; Headington Hill, near Oxford; 



* Memoirs of the Geol. Survey, Expl. of Sheet 13, p. 5, by Messrs. Hull and 

 Whitakee. 



