THE CEPHALOPODA 
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TRIBE 2. PROSIPHONATA. 
The siphuncular necks project in front of the septa. The septal 
sutures present deeply indented lobes and saddles. 
Faminty 1. Arcestrpar. Globular and smooth or nearly smooth 
forms, with a reduced umbilicus; the terminal chamber very deep, 
occupying nearly a whole whorl of the spire; an aptychus present. 
Genera — Popanoceras, Gemmellaro; Permian.  Cyclolobus, Waagen ; 
Permian. Arcestes, Mojsisovics; Trias. Lobites, Mojsisovics; Trias. 
Faminy 2. Tropitrpar. The shells globular, but differing from those of 
the Arcestidae in having radiating and tubereulated costae. Genera— 
Thalassoceras, Gemmellaro; Permian.  Tropites, Mojsisovics; Trias. 
Sibirites, Mojsisovics ; Trias.. Faminy 3. CeRaAtiTiIpAr. Shells coiled, 
with a large umbilicus; the terminal chamber short; sutures with 
simple saddles. Genera—Trachyceras, Laube; Upper Trias.  Ceratites, 
de Haan; Trias. Dvinarites, Mojsisovics; Trias. Some genera with 
helicoidal shells are related to these coiled forms, viz. Cochloceras, 
Hauer; Trias: also some straight forms, e.g. Rhabdoceras, Hauer; Trias: 
they have been placed in distinct families by some authors. Famrty 4. 
PINACOCERATIDAE. Shell compressed, smooth ; the terminal chamber 
short; the suture very complicated, convex. Genus — Pinacoceras, 
Mojsisovics; Trias. Faminy 5. PHyLLOCERATIDAE. Shells coiled, the 
whorls overlapping one another ; the suture formed of numerous lobes 
and saddles. Genera — Phylloceras, Suess; Jurassic. Rhacophyllites, 
Zittel. Famity 6. Lyroceratmar. Shell discoid, the whorls loosely 
united or uncoiled ; the sutures deeply indented but with only three 
saddles and lobes. Genera—-Lytoceras, Suess; Jurassic and Cretaceous. 
Macroscaphites, Meek; uncoiled and recurved; Cretaceous. Hamites, 
Parkinson ; flexed three times; Cretaceous. Ptychoceras, d’Orbigny ; 
Cretaceous. T'wrrilites, Lamarck ; coiled in a sinistral helicoidal spire ; 
Cretaceous. aculites, Lamarck; the adult straight and elliptic in 
section; Cretaceous. Faminy 7. Ammonitipar. Shell coiled, with 
narrow whorls which do not embrace one 
another ; aperture simple; a horny anapty- 
chus present. Genera—Ammonites, Lamarck ; 
Jurassic. Arvetites, Waagen ; Jurassic. Aego- 
ceras, Waagen, Lias. Faminy 8. HaRrpocera- 
TIDAE, Shell discoid and flattened, with a 
carinated border ; the aperture provided with 
lateral projections; a calcareous aptychus, 
formed of two pieces. Genera—Huarpoceras, Fic. 294. 
Waagen ; Jurassic. Oppelia, Waagen ; Jurassic. Morphoceras pseudoanceps, right- 
Lissoceras, Bayle ; Jurassic and Cretaceous, side view. 4.0, orifice for arms ; 
e.0, eye-orifice ; s.b.0, infundibulo- 
Faminy 9. AMALTHEIDAE. Shell flattened, buccal orifice.’ (After Douvillé.) 
with a prominent carina continued anteriorly 
into a rostrum. Genera—Amaltheus, Montfort; Lias. Cardioceras, 
Neumayr ; Jurassic. Schloenbachia, Neumayr ; Cretaceous. Faminy 10. 
STEPHANOCERATIDAE, Shell not carinated, but with radiating costae, 
which are often bifurcated ; aperture often provided with lateral pro- 
