PLATE XXIV. 

 Omtroceras columnare, Hall, 



Page 411. 



Ftg. 1. View of a very fine specimen of this species, showing the surface markings, form of the 

 septa, size and proportions of the siphuncle. From a specimen in the collection of 

 Prof. Marcy. 



Orthoceras annvlatvm, Sowerby. 



Page 411. 



Fig. 2. A specimen (a cast of the interior) of this species, showing the septa and siphuncle. 

 " 3. A fragment, showing the angular form of the annulations and the lines of the septa. 

 " 4. A fragment, showing the transverse or concentric undulating strise, and the longitudinal 

 ridges, forming nodes where they cross the annulations. 



Otrtoceras laterale. Hall. 



Page 407. 



Fig. 5. View of a specimen of this species, showing a few of the septa, and the outer chamber 

 strongly constricted below the aperture. This figure is erroneously referred in the 

 text to 0. alienum. 



Orthoceras alienuim, Hall. , 



Page Hi. 



Fig. 6. View of a cast of the outer chamber of this species, showing the gradually tapering form 

 and the broad constriction near the aperture. 

 " 7. A section of a fragment, showing the septa and siphuncle. 



