76 AMMONITID&. 
LILLIA, Bayle, 1878. In the young shell the ribs are simple or 
bifurcated, commencing with tubercles at the umbilical region ; 
later the ribs are simple and the shell resembles Agassiziceras. 
Perhaps this group would be better placed near Harpoceras : 
the limit between the latter genus and Ammonites is very diffi- 
cult to trace, without the aid of the aptychus. 
AHGOCERAS, Waagen, 1869. 
Syn.—Myecroceras, Hyatt, 1867. Androgynoceras, Hyatt, 
1867. Liparoceras, Hyatt, 1867. Deroceras, Hyatt, 1867. Per- 
onoceras, Hyatt, 1867. Platypleuroceras, Hyatt, 1867. Cyclo- 
ceras, Hyatt, 1867. Psiloceras, Hyatt, 1867. 
Distr.—4 Cretaceous, 54 Liassic species. A’goceras (Micro- 
ceras) biferum, Quenst. (xxxvii, 96, 97). Av. (Androgynoceras) 
aun: Hyatt (xxxvi, 83, 84). 4. (Lyparoceras) Henley, 
Sowb. (xxxvi, 85). 4. (Deroceras) Ziphius, Ziet. (xxxvii, 95). 
4. (Peronoceras) muticum, V’Orb. (xxxvili, 13, 14). di, (Platy- 
pleuroceras) latecostatum, Sowb. (xxxviii, 19). 4. ( Cycloceras) 
Valdani, d’Orb. (xxxix, 34,35). 4. (Psiloceras) psilonotum, 
Quenst. (xxxvil, 2, 3). 
Shell mostly compressed, composed of many whorls, embra- 
cing but little, sometimes provided with nodose or externally 
bifureate ribs; never with true sickle-like ribs; not carinate ; 
body-chamber usually a whorl long, in the geologically young an 
forms somewhat shorter. Aperture simple without lateral ap- 
pendages, with very weak external lobes and a constriction; a 
single corneous aptychus. Lobular line strongly notched, upper 
lateral longer than the siphonal, lower lateral not always present ; 
usually with a depending siphonal lobe. Lobular bodies narrow, 
not wedge-shaped ; antisiphonal two-pointed. 
The true Agoceras died out in the middle Lias. 
Mgoceras corresponds to the group Ammonites Capricorni ot 
Buch. 
SCHLOTHEIMIA, Bayle, 1878. Ribs meeting exteriorly, where 
they form an angle directed towards the aperture. 4. angu- 
latum, Schloth. 
Lytocere, 
Body-chamber short, two-thirds of the last whorl; aperture 
simple. No aptychus. 
LyToceras, Suess, 1865. 
Syn.—Thysanoceras, Hyatt, 1867. 
Distr.—62 species from the Trias, Jura and Cretaceous. J. 
Henleyi, Sowb. (xxxvi, 85). ZL. Moreleti, Hauer (xxxviii, 28, 29). 
L. (Thysanoceras) fimbriatus, Sowb. (xxxiii, 45, 46). 
Shell flattened, discoidal, whorls but little involute or simply 
in contact ; body-chamber two-thirds of a whorl, margin of aper- 
