PLATE IX. 



Zone of Arietites Bucklcmdi. 



Fig. 1. Arietites rotiformis, Sowerby. Lateral view of a fine specimen, natural size, 

 with the shell preserved, from the Lower Lias de I'Auxois, Semur, Cote-d'Or; 

 kindly given me by Monsieur J. J. CoUenot, of Semur, to illustrate this work. 



2. Front view of the same specimen, natural size, to show the siphonal area and 



depth of the bisulcations, with the spine-like character of the tubercles. 



3. An accurate outline of the foliations of the septa magnified. 



