80 AMMONITID&. 
discoidal, spiral shell, and evolute, with discoidal, helicoid or 
straight shell, the whorls unwound partly or entirely. This 
evolution is partly generic, but in some instances is known to be 
accidental: thus specimens ot Acanthoceras angulicostatum, d’Orb. 
have the whorls slightly embracing, or merely in contact (Lyto- 
ceras), or completely detached (Crioceras). 
Normal. 
STEPHANOCERAS, Waagen, 1869. 
Syn.—Dactylioceras, Hyatt, 1867. Globites, de Haan, 1825. 
Orbulites, Lam., 1801. Spheeroceras, Bayle, 1878. 
Distr.—41 Jurassic sp. 8S. (Dactylioceras) annulatum, Sowb. 
(xxxiv, 47, 48). S. Blagdeni, Sowb. (xxxiv, 57, 59). 
General form of the shell very variable, external side rounded 
without keel, angle or furrow. Sculpture never sickle-shaped, 
decorated with straight, bifurcating ribs, abundantly provided 
with nodes or swellings. Margin of aperture simple or with ears 
mostly formed of a broad, smooth zone; aperture frequently 
constricted. Body-chamber one to one and one-quarter whorls 
long. Lobes usually deeply divided, siphonal and upper lateral 
lobe usually of the same length; a stout auxiliary sutural lobe; 
lobular bodies narrow. Aptychus divided, calcareous, very thin, 
covered with granules on the external surface. 
Stephanoceras diverges from Aigoceras with Steph. pettos in 
the middle Lias ; according to the subdivision into groups, it 
embraces the Liassic Planul: ata, Coronata and Bullata after the 
exclusion of some heterogeneous elements; the last represen- 
tatives come from the Oxfordian (Steph. Collini, Opp., glomus, 
Opp.). 
CADOCERAS, Fischer, 1882. Shell much swollen; umbilicus 
narrow, carinated ; last whorl entirely smooth, preceding whorls 
with ribs forming an angle directed forwards in the ventral 
TESION. 1a. modiolare, Luid. 
PROTOPHYTES, Ebray, 1860. Last whorl geniculated, embracing ; 
umbilicus transverse, linear; ribs interrupted at the periphery ; 
aperture with a peripheral appendage, triangular, wide and thick. 
S. Oxfordianum, Ebray. : 
c«coprycHius, Neumayr, 1878. Last whorl geniculated, em- 
bracing ; lateral ear-like projections short and narrow; a cowl-like 
ventral appendage. QU. refractus, de Haan. 
MORPHOCERAS, Douvillé, 1880. Whorls rounded with radiating 
ribs uniting in groups of one to three near the umbilicus, which 
is scalariform in the juvenile, and much widened in the adult ; 
aperture geniculated, almost completely closed by the expansion 
of the lateral ears, which unite at the median line on one side 
and on the other touch the preceding whorl; thus there are, so 
to say, five apertures, the peripheral, two small ones, placed each 
