﻿BRITISH FOSSIL CEPHALOPODA. 



Plate XVI. 



Fig. 



1. Orthoceras perversum. — From the Upper Ludlow, Ludlow. In the Museum 



of Owens College, Manchester, a, one of the septal surfaces, showing 

 the unsymmetrical siphuncle. 



2. Ibid. — From the Lower Ludlow, Ludlow. In the Museum of the Geological 



Society. The specimen figured by Sowerby as 0. imbricatum. 



3. Orthoceras (Tretoceras) bisiphonatum. — From the Lower Llandovery rocks, 



Llandovery. In the Museum of the Geological Society, a, the septal surface, 

 showing the true diameter ; b, side view of a siphuncular bulb. 



4. Ibid. — From the Woolhope Beds, Woolhope district. In the collection of Dr. 



Grindrod. A specimen corresponding to "Actinoceras baccatum." 



5. Orthoceras (Conoceras) eoum. — From the Arenig rocks, Shelve. In the 



Museum of Practical Geology, a, a portion enlarged. 



