206 
F14. 61. Fic. 62. 
Stephanoceras Brackenridgii, showing labial prolongations. 
In Steph. Blagdent, fig. 59, and Steph. Humphriesianum, the 
mouth is encircled by a thick band, from whence the strong 
ribs in these species is derived. The dwelling-chamber is from 
one to one and a quarter whorls in length. The suture-line is 
much ramified. The siphonal and principal lateral lobes are 
nearly of equal length; the lower lateral is much smaller, and 
there are several branched auxiliaries. There is considerable 
diversity among the species. The genus Stephanoceras appears 
to have certain genetic relations with group Involuti of the genus 
Aegoceras of the Middle Lias. Many characteristic species 
appear for the first time in the Upper Lias, as Steph. annulatum, 
Sow. fig. 68, and Steph. commune, fig. 64, with Steph. crassum, 
Steph. fibulatum, and Steph. Hollandrei, all from the same beds. 
The zone of Steph. Humphriesianum, Inferior Oolite, is one great 
depository of the species both in France and England. We 
have the following list therefrom :— 
Fic. 63.—Stephanoceras annulatum, Sow. Fic. 64.—Stephanoceras commune, Sow. 
