AMMONITIDZ. 85 
Cretaceous, with the exception of Scaphites, Turrilites and 
Baculites. Neumayr has divided them into two groups: Ham- 
ites, applying to the species approaching Lytoceras by their 
ornamentation, and their sutural line having lobes symmet- 
rically divided into pairs; Crioceras, containing the forms 
having the ornamentation of Acanthoceras, with lobes not sym- 
metrically divided. Fischer arranges them in the following sub- 
genera or sections, some of which are considered genera by 
other systematists : 
MacroscapuiTEs, Meek, 1876. Shell with inner turns merely 
in contact, or so slightly embracing as to leave a very large, 
shallow umbilicus; periphery rounded; body portion much ex- 
tended from the inner volutions; surface costate. S. gigas, 
Sowb. 
ANCYLOCERAS, d’Orb., 1842. Shell at first spiral, discoidal 
with separated whorls; afterwards produced at a tangent and 
then bent back again upon itself like a hook. 41 sp. Infer. 
Oolitic, Cretaceous ; Europe, South America, United States. H. 
spinigerus, Sowb. (xxxii, 33), Gault, Folkestone. 
ANISOCERAS, Pictet, 1854, Shell at first spiral, helicoid, whorls 
separated, at length more or less prolonged and reflected ; trans- 
versely ribbed ; sutures of septa with five lobes and saddles, all 
bipartite. 12 sp. Gault to Upper Greensand; Europe. Creta- 
ceous, Jurassic; India. H. Sausswreanus, Pictet (xxxii, 34). 
HAMITES, Parkinson (restricted). Shell conical, hook-shaped, 
bent upon itself more than once, the courses separate. 38 sp. 
Chalk ; Europe, 8S. America. 
HAMULINA, d’Orb., 1849. Differs from Hamites in being only 
once bent upon itself, not in contact. 20sp. Neocomian ; France. 
Gault (?); India. H. trinodosa, d’Orb, (xxxiii, 42). 
PTYCHOCERAS, d’Orb., 1840. Shell bent once upon itself; the 
two straight portions in contact. 8 sp. Neocomian to Creta- 
ceous; Europe, India, United States. H. Emericianus, VOrb. 
(xxxiii, 43). France. 
DIPTYCHOCERAS, Gabb, 1869. Three straight limbs in contact. 
A Ptychoceras in every respect except that it has an additional 
limb which incurves, enveloping both the preceding to a slight 
degree only. Meek considers it doubtfully identical with Ptycho- 
ceras. 
TOXOCERAS, d’Orb., 1840. (Taxon, a bow, ceras, a horn.) Shell 
horn-shaped or curved ; the six lobes and saddles of the sutures 
simply crenulated; last chamber large. Connected with Crio- 
ceras and Ancyloceras by numerous intermediate forms. 20 
sp. Neocomian; France. H. bituberculatus, @’Orb. (xxxii, 32). 
CRIOCERAS, Leveillé, 1836. Shell diseoidal, whorls not contig- 
uous, but in the same plane. 13 sp. Neocomian to U. Green- 
sand; Europe. Some of the species are believed to be merely 
