AMMONITID&. ort 
ture at the columellar side produced into a lobe, processes 
wanting at the siphonal side and on the flanks ; lines of growth 
and sculpture parallel to the margin of the aperture, at the suture 
bent forwards ; sculpture feeble, mostly consisting of radial lines 
or interruptions; sutural line with few lobes, lateral lobes and 
saddles symmetrically divided, columellar lobe two-pointed. No 
aptychus. 
The forms of the Trias diverge herefrom in such a way, that 
in them the lines of growth and sculpture, as in Phylloceras, are 
directed forward at the siphonal side, and that the structure of 
the saddles is monophyllic. 
Lytoceras corresponds to the Fimbriati group of Ammonites. 
MONOPHYLLITES, Mojs., 1879. Differs in the saddles being 
monophyllic. JL. spherophyllum, Hauer. 
OPHICERAS, Griesbach, 1881. Compressed; section of whorls 
oval and widening near the umbilicus, the latter large and shal- 
low ; thick, covered with fine wrinkles or growth-lines of sigmoid 
shape, becoming fine ribs in the body-chamber; at irregular 
intervals the shell swells into rounded bumps, largest near the 
umbilical margin; the periphery is rounded, and the wrinkles 
or folds run across it and join with those of the other side. 
Both in general shape and number and arrangement of the lobe- 
lines, this subgenus closely resembles the Lytoceratite groups 
Monophyllites and Phylloceras, and it may be said to be an 
earlier stage of those forms. C. Tibeticum, Griesb. (xl, 45). L. 
Trias; Himalayas. 
PHYLLOCERAS, Suess, 1865. 
Syn.—Rhacoceras (Agassiz), Hyatt, 1867. 
Distr.—i7 sp. Triassic, Jurassic, Cretaceous. P. ocultum, 
Mojs. (xxxix, 38, 39). P. (Rhacoceras) heterophyllum, Sowb. 
(xxxiv, 51, 52). 
Shell discoidal, involute, with feeble sculpture, sometimes with 
constrictions or varices, lines of growth directed forwards ; 
body-chamber short, margin of aperture simple with somewhat 
produced lobes on the external side ; no aptychus ; lobes numer- 
ous, diminishing regularly in size, laterals without subdivision 
into principal paired branches; leaves or lobes of the saddles 
very much rounded; antisiphonal lobe two-pointed. 
This genus is remarkable for its persistence in the secondary 
strata. The triassic forms are characterized by their less numer- 
ous lobes, and more open umbilicus. Prof. Meek includes a few 
American cretaceous species in the genus. 
Harpocerate. 
Aperture with more or less developed lateral ear-like prolon- 
vations ; sutural line with accessory lobes ; surface ornamented 
