SUB-ORDER E CYRTOCHOANITES 527 
Cenoceras. Sutures slightly inflected, with faint ventral lobes ; annular lobes present. 
Volutions sub-globose, and umbilical perforation comparatively large. 
Siphuncle centren in the apical camera, but later becoming ventrad 
of centre. Tertiary (?) to Recent. 
Sub-Order E. CYRTOCHOANITES. Hyatt. 
Shells varying from orthoceracones to nautilicones, none of them 
highly ornamented, although some are annulated*or costated, and in 
rare cases slightly nodose. Sutures as a rule simpler than in Ortho- 
‘choanites. Siphuncle varies exceedingly, passing from tubular in the 
young and even in the full-grown of primitive forms to highly nummu- 
loidal in the adults of specialised genera, or again tn some groups 
retaining constantly its primitive character. The funnels, however, 
are as a rule bent outward or crumpled, and generally short. 

Fic. 1076. 
Ae. See Nautilus Geinitzi, 
I, ANNULOSIPHONATA. Pietet. _ Tithonian ; 
i Stramberg, Moravia. 
Mostly orthocerucones and cyrtoceracones, with a few gyroceracones 
and very rarely nautilicones, the last-named being invariably discoidal. Apertures 
constantly open. Siphunele may be empty, but organic deposits when present always 
gathered about or encrusting the funnels as hollow or solid internal rings. Deposits 
sometimes sufficient to form more or less annulated endosiphuncles, the rings being opposite 
the camerae, alternating with the septa, and extending outwardly. 
Family 1. Loxoceratidae. 
Smooth orthoceracones and cyrtoceracones similar to Orthoceratidae, but siphuncle 
distinctly nummuloidal, and funnels very short and crumpled. Deposits not uncommon, 
but irregular, and only irregular endosiphuncles occasionally formed. 
Lowoceras, M‘Coy (Sactoceras, Hyatt). Mostly orthoceracones, circular or elliptical 
in section. Siphuncle supposed to be tubular in the young, but highly nummuloidal 
in later stages, centren or near the centre. Septa invariably single, and camerae 
empty. Ordovician to Carboniferous, 
Campyloceras, M‘Coy (Aploceras, Hyatt). Breviconic cyrtoceracones or orthocera- 
cones with smooth or finely ridged shells, circular or depressed elliptical in section. 
Siphuncle centren or ventrad of centre. Carboniferous. 
Family 2. Uranoceratidae. 
J 
Cyrtoceracones, gyroceracones, and nautilicones with stout volutions. Siphunele in 
primitive forms highly nummuloidal, but invariably empty ; in nautilicones it has less 
nummuloidal segments, and is uniformly ventrad of centre, but not near the venter. 
Sutures with ventral saddles, lateral lobes, and also dorsal saddles in primitive forms as 
well as the young of all shells, Ventral and dorsal lobes arise subsequently in the 
ontogeny of nautilicones, 
Uranoceras, Hyatt. Stout, more or less breviconic eyrtoceracones, compressed 
a) d d v ? 
elliptical or sub-quadrangular in section. Sutures with broad ventral saddles, lateral 
and dorsal lobes. Siphuncle large, nummuloidal, centren or ventrad of centre. 
Devonian and Carboniferous. 
Gigantoceras, gen, noy. Gyroceracones similar to the preceding, but having longer 
living chambers and more compressed volutions. Includes the largest known Nau- 
tiloid shells. Type G. (Gyroc.) inelegans, Meek sp. Silurian. 
