PLATE 21. 



Pago. 



Fig. 1. Ancvloceras uncum - 40'J 



1,«. A fragment of the non-septate portion, side view (type). 



1, b. A section of the same, showing its ovate form. * 



Fig. '2. Heteroceras? Cheyennense 483 



2, a. A fragment of the non-septate portion (type-specimen). 

 2, b. A different view of the same, showing nodes. 



Fig. 3. Heteroceras .' angulathm 434 



:'.,</. A non-septate fragment (type-specimen). 



'■'. b. A different view of the same. 



.;.<:. A section fchowing the last septum. 

 Fig. 1. Heteroceras ? (sp. uudt.) 



4.o. A peripheral view of a part of the hody-chamber. 



i.b. A different view of same. 



