AMMONITIDiE. 81 



septate part, but not curving over the aperture. B. incurvatus^ 

 Dujardiu. 



CYRTOCHTLUS, Meek, ISTG. Shell straight ; aperture opening 

 towards the antisiphonal side, and the lateral sin vises of the lip 

 excavated in the opposite direction ; projection of siphonal margin 

 of lip abruptl}" arching over the aperture, and the antisiplional 

 margin of same deeply sinuous instead of convex in outline; 

 interior with regularly disposed ridges, leaving oblique constric- 

 tions on internal casts. Hamites baculoides, Mantell = B. obli- 

 qtiatus, Sowb. 



Bacultna, d'Orb., 1847. 



Distr. — 2 sp. Jurassic, Lower Chalk ; Europe. B. arcuaria, 

 Quenstedt (xxxii, 24 \ 



Shell straight, point conical ; sutures of septa a row of rounded 

 lobes, toothed at base. 



