ee ee — Se 
worm See eS 
} 
~ Peo & 
she i an 
177 
must refer to the plates of these species, and the descriptive 
text thereof in my monograph, for many important details 
concerning the mouth-borders of Harpoceras. 
Fie. 20.—Stephanoceras 
Deslongchampsii. 
Sa ehariaerae Braikenridgii, showing labial pegmatite 
In Stephanoceras the shell varies in form; the siphonal or 
abdominal area is, in general, rounded and without a keel or 
furrow, and the lateral ribs terminate in tubercles on the sides, 
from whence numerous folds branch out and extend over the 
abdomen to join their fellows from the opposite side. The 
mouth-border in Stephanoceras Deslongchampsii consists of a 
round band which encircles the aperture, as in fig. 20, and, by 
its prominence and inflexion on the sides, forms the thick lateral 
portion of the ribs up to the tubercles, which are prominent in 
this species. In Stephan. Humphriesianum the oral band is more 
voluminous, and in like manner as the mouth was developed 
onwards, the receding band formed the ribs and tubercles so 
well shown in that Ammonite. In Stephan. Braikenridgii the 
sides of the border develop long, inflected, lateral lappets, which 
