LITUITID^. 
9 
the outer margin. The principal ornaments in all the known species 
are prominent transverse ribs. 
Ojyhidioceras has a very limited range, being known only in the 
Silurian of England and Bohemia. 
Ophidioceras simplex, Barrande. — a, lateral view of an adult specimen, showing 
the lobecl aperture ; h, convex side of the same, showing the smaller 
orifice, and the band or keel corresponding with it ; c, front view of the 
same, showing the contracted border of the larger orifice ; d, aperture 
viewed from above, showing its trilobate character, oriented to correspond 
with a ; e, fragment of the band of 0. lesscllatiis, Barr., showing its concave 
form and ornaments. Copied from Barrande, Syst. Sil. de la Boheme, 
vol. ii. pt. i. 1865, pi. xcvii. If. 6-9 & 19. 
Remarli's. Ophidioceras was considered by Barrande to be a sub- 
genus of Lituites ; but Professor Blake \ who apparently is not con- 
vinced of the presence of lobes in the aperture of the latter, as 
described (though from imperfect material) by Lessen^ and IN^oet- 
ling regards Ophidioceras as a distinct genus, only “ remotely 
related to Lituites. Hyatt places Ophidioceras “ provisionally 
near Ascoceras [i. e. in the same family, Ascoceratidoi] on account of 
the Y-shaped aperture and form of whorl and costations ; ” but the 
extraordinary changes which the shell of Ascoceras passes through 
in the course of its growth, added to its peculiar septal characters, 
mark it off very distinctly from Ophidioceras whose alliance seems 
to be clearly with Lituites. % 
British Foss. Ceph. 1882, pt. i. pp. 67, 68. 
Zeitschr. der Deutsch. geol. GeselL, Band xii. 1860, p. 15. 
® Ibid. Band xxxiv. 1882, p. 156. 
^ See on this point Barrande, Syst. Sil. de la Boheme, vol. ii. 1877, Supplem. 
et Serie tardive, p. 98, pi. ccccxci. ff. 3-7 ; also Lindstrom, Geol. Mag. dec. iii. 
vol. V. (December, 1888), p. 532. 
