240 



THE LIAS AMMONITES. 



Genus Ptychites, v. Mojs. — In its general form and length of the body-chamber it 

 resembles Arcestes, but differs from that group in the structure of the lobes. The 

 external lobe is very shallow, the external saddle very short, the first lateral saddle is, on 

 the contrary, very high ; the saddles are indented, and show an appearance of a branched 

 formation. The smooth shell is covered with straight or winding radial folds. The 

 species are all Triassic. Ex. Ptychites Studeri, Hauer, Ptychites Bontianus, Hauer. 



Genus, Pinacoceeas, v. Mojs. — Shell small, with a high mouth-opening, surface 

 smooth, rarely with any elevations thereon ; body-chamber from one half to two thirds of 

 a whorl long. Mouth-border with short lappet-formed processes on the ventral side. 

 Lobe-line distinguished by the presence of an additional external lobe. The species are 

 all Triassic. Ex. Pinacoceras imperator, Hauer, Pinacoc. Daonicum, Mojs. 



Genus Sageceras, v. Mojs. — In the form of the shell and length of the body- 

 chamber this genus is nearly related to Pinacoceras. It is distinguished from it by the 

 structure of the " wrinkle-layer," the form of the lobes, and the direction of the lines of 

 growth on the concave part of the shell. The " wrinkle-layer " is granular, as in Nautilus, 

 and does not consist of long lines and threads as in other Arcestidce. The saddles are 

 small, strongly margiuate, or linguiform; the lobes symmetrical with simple conical 

 indentations, single or double ; there are three lobe groups as in Pinacoceras. Three 

 species belong to the Permian formation, Sat/. Hatterinum, Kon., Say. Orbignyanum, 

 Vern.j /Sfey.jormas, Waag., the others are found in the Triassic rocks, Sag. Gabbi, Mojs,, 

 Sag. Haidivgeri, Hau., Sag. Walteri, Mojs., Sag. Zigmondyi, Mojs. 



Genus Amaltheus, Montfort. — Siphonal side of the shell sharpened or keeled ; ribs, 

 when present, flexed forward, and ending in a granular (fig. 135) or plaited ridge or keel 

 (fig. 134); the external shelly lamina in some species develops fine spiral lines; body- 



FiG. \Zi.—Amaltheus margaritatus, Mont. 



Fig. 135. — AinaUhi^ixs cordatus. Sow. 



chamber short ; one half to two thirds of a whorl. Mouth-border simple, ventral portion 

 ending in a long projecting process. Lobe-line extremely ramified, the siphonal lobe 



