196 
THE LIAS AMMONITES. 
the siplional area compressed tubercles, which collectively represent a series of crests. 
Septa formed of lobes divided into single parts, and of saddles divided into pairs of parts. 
Siphonal lobe nearly equal in length to the inferior lateral lobe, lloplites Brottianus, 
d'Orb. (fig. 78), from the Lower Cretaceous Rocks, is a good type of this section. 
8th Section. Rhotomagenses, dfOrhigny. Shell with inflated whorls, square or 
oval, ornamented with prominent ribs, more or less tuberculated upon four or five lines, 
one of which runs along the median line of the area, and renders it more or less 
angular. Septa formed of lobes and saddles partly divided into pairs. The siphonal 
lobe longer than the superior lateral. The species characterise the Middle Cretaceous 
Formation, and Hoplites Deverianus, d'Orb. (fig. 79),' from the Upper Greensand, is a 
good type of this section. 
e. Species with the siphoial area excavated, and provided with tubercles on the sides. 
9th Section. Dentati, von Buch. See p. 192. 
10th Section. Ornati, von Buch. See p. 19:3. 
/. Species toith the siphonal area more or less square. 
11th Section. Elexuosi, von Buch. See p. 193. 
12th Section. Compressi, d'Orhigny. >5'/ie// in general very 
much compressed, composed of large whorls, highly involute. 
Sides provided with radii or fine striae, all slightly flexed, and 
passing on to the margin of the siphonal area, where they develop 
small tubercles. Siphonal area narrow and squarely truncated. 
Sefta composed of a great number of lobes formed of single parts, 
and of saddles often formed of pairs of parts. Siphonal lobe very 
large, much longer than the superior lateral. These Ammonites all 
appertain to the different divisions of the Cretaceous Formation, 
Cos. Beaumontiamm, d'Orb. Cos. Beaumonfiamwt, d'Orb. (fig. 80), from the Lower Chalk, is a 
good type. 
13th Section. Armati, von Buch. See p. 191. 
14th Section. Angulicostati, d'Orhigny. /57^e// thick, with whorls almost round, each 
side of the siphonal area ornamented throughout with slight ribs which make this part 
