74 AMMONITID&. 
S. cristata, Deluc. (xxxv, 67). S. (Mortoniceras) vespertinus, 
Morton = S. Texanus, Roemer (xxxvi, 86). 
This genus embraces the very natural group of Cristati; to 
these may be added Schl. Germari, Reuss., whose aftinity to 
these is indicated, besides other striking characters, by a toothed 
keel. Shell strongly keeled, usually with strong ribs curved 
forwards on the flanks ; body-chamber two-thirds of a whorl long, 
drawn out at the sickle-shaped aperture into a long, beak-like 
process, which is either prolonged in conformity with the curva- 
ture of the spiral or bent outwards. Siphon very stout, usually 
lying in the keel, which is often cut off from the lumen of the 
shell by a calcareous septum. Lobes not much branched, with 
bodies which are narrower than the saddles; only one distinct 
auxiliary lobe; which is wanting in some forms. Siphonal lobe 
usually as long or longer than the first lateral. In some species 
a great reduction in the number of branches of the lobes takes 
place, so that they approach a Ceratitic form. (Schl. senequeri 
and halophylla.) 
PLACENTICERAS, Meek, 1870. 
Distr.—Cretaceous ; United States, India. A. placenta, DeKay 
(xxxvi, 82). 
Shell with the very narrow periphery truncated, and often 
provided with a row of compressed alternating nodes along each 
margin; volutions about three-fourths embraced by the next 
succeeding outer one; septa with the lateral sinuses provided 
with more or less branched and digitate terminal divisions ; 
umbilicus small or moderate. 
SPHENODIScUS, Meek, 1872. Shell with periphery cuneate; 
umbilicus very small; volutions each almost entirely embraced 
by the succeeding one; septa with the first five or six lateral 
sinuses provided with only a few short, nearly simple, obtuse 
divisions ; while the others are simple, and usually broadly reni- 
form at the ends. Cretaceous; United States, Europe. Amm. 
lobatus, 'Tuomey. 
Meek thinks that some of the species of Pinacoceras, Mojsi- 
sovics, will fall into this group; and that that genus is too 
comprehensive. Sphenodiscus equals the Clypeiformi group 
of Ammonites. : 
NEOLOBITES, Fischer, 1882. Shell flattened, sharply carinated ; 
lobes and saddles simple, not truncate, resembling those of the 
triassic Lobites. P. Vibrayeanus, d’Orb. Cenomanian. 
Bucuiceras, Hyatt, 1875. 
Dedicated to Dr. L. von Buch, a German naturalist. 
Distr.—Cretaceous. B. Syriacum, Buch. 
Shell ornamented with strong ribs, dichotomous, from tuber- 
cles near the umbilicus ; ribs interrupted at the periphery ; lobes 
