PLATE 8 4. 



Page. 



Fig. 1. Placenticeras (Sphenodiscus) lenticulauis 473 



I, a. A yonng septate specimen, or I lie inner volutions of an adult, side view. 

 1,5. Another view of the same, showing by the section of the outer volution I he sagittate 

 form of the aperture, and the compressed general fornrof the shell. [The edge, of 

 the periphery in this figure should be acute, instead of apparently slightly trun- 

 cated . ] 



1, c. A septum, natural size, from a larger specimen. 



Fig. 2. Scaphites Nicojxetii 13.~> 



2, a. A peripheral and aperture view of a specimen consistiug of the inner volutions. 



2, b. A side view of the same. 



Fig. 3. Scaphites Conradi, oar. intermedios 433 



3, a. A peripheral and aperture view of the type-specimen of this variety. 



3, l>. A side view of same. 



'.!, c. A septum of same, rragnifted to a little more than two diameters. 



Fig. 4. Scaphites Nicoixetii 135 



1, a. A side view of a specimen retaining most of the outer volution. 



1, 6. A peripheral and aperture view of same, the lip being partly restored. 



4, c A septum of same, two and a half diameters. 



