igog AMMONITES EXARATUS 5c 



Comparable Species 



Harpoceras exaratum ; Blake, 1876, 11, 5, has a smaller umbilicus 

 than the subject. 



H. exaratum ; Wright, Mon., 1882, LXii, 1-3, is a form more cata- 

 genetic than the subject — a further development of stage 3, with a 

 smaller umbilicus. It is in the same degree of development as 



Am. elegans, J. Sowerby, 1815, xciv, i, which, however, may possess 

 a more triangulate aperture. 



Harpoceras lythense ; Hug, 1898, in, i. 



