AMMONITES Gulielmii. 

 TAB. CCCXI. 



Spec. Char. Lenticular, with a narrow front, 

 radiated ; volutions exposed ; radii dissimilar, 

 terminating' in small tubercles, principal radii 

 furnished with two tubercles near their com- 

 mencement. 



A. VERY flat shell, bordered by two rows of tubercles 

 that terminate the radii upon the edges of a flat front : 

 the longer radii have each a tubercle at the commence- 

 ment and another at about one-third their length, where 

 they divide and alternate with shorter radii : they are all 

 arched and rather acute ; the aperture is elliptical, rather 

 more than one-third as wide as long. 



A very elegantly marked Ammonite ; the specimen 

 retains part of its pearly shell with the coat over it : 

 some of its volutions are filled with Carbonate of Lime, 

 others with Iron Pyrites. Dr. W. E. Leach kindly pre- 

 sented it to me some years ago ; I suspect it was found 

 in the clay above the Kelloways Rock. 



This elegant shell I have named after one of my oldest 

 Oxford friends. Dr. George WiUian\s, Regius Professor 

 of Botany, an assiduous lover of science and every 

 good, a commemoration which will, I have no doubt, 

 gratify many, who, when thinking of him, will feel as I 

 do a reviving pleasure and esteem. 



