522 MOLLUSCA SUB-KINGDOM VI 
narrow concave venter, and umbilicus small or closed. Sutures with prominent 
ventral saddles undivided by ventral lobes in adult shells.. Trias. 
Hercoglossa, Conrad (Enclimatoceras, Hyatt), (Fig. 1068). 
Deeply involute,- with sutures like those in Glyphioceratidae, but 
the ventral saddle not divided by even the shallow lobe usually 
found in that family. Annular lobes present only in some 
species. Siphuncle small, centren or dorsad of centre. Trias to 
Tertiary. 
Pseudonautilus, Meek. Similar to Hercoglossa, but with lobes 
on the venter, and two saddles on either side. Large annular 
lobes present. Jura. 
Aturia, Bronn (Fig. 1069).. Similar to Hercoglossa, but with 

and funnels very long and larger than in any genus of Mesozoic 
or Tertiary Nautiloids. Eocene and Miocene. 
Fic. 1069. 
Aturia Aturi, Bast. sp. 
Miocene; Bordeaux. TV. RytTIcERATIDA 
Shell broken open to aon a. 
show siphonal funnels. : rhs! A 
Cyrtoceracones, gyroceracones, and nautilicones having shells 
covered with more or less projecting bands of growth which often become sinuous or develop 
into spout-like, spinous, or nodose prominences. In the more specialised shells these are apt 
to be confined to the venter. The frills in the bands often form coarse longitudinal ridges. 
Siphuncle tubular or slightly nummuloidal, and commonly ventrad of centre. 
Family 11. Halloceratidae. 
Orthoceracones and cyrtoceracones having depressed elliptical or subtrigonal sections, 
venter broader than the dorsum. Shell with closely set and frilled projecting bands of 
growth, having large ring-like bands at intervals that sometimes expand so as to form 
wide collars. The highly specialised nautilicones may have a row of large nodes on 
cither side springing from the bases of large spout-like spines. Sitphuncle tubular, small, 
and near the venter. 
Zitteloceras, Hyatt. Cyrtoceracones of depressed elliptical section, the venter 
narrower and more gibbous than the dorsum, The layers finely frilled and closely 
set in the intervals between more prominent annular bands. Ordovician to Devonian. 
Halloceras, Hyatt. Gyroceracones of sub-trigonal section, the venter broad and 
dorsum sub-angular, with one row of large nodes at each of the ventro-lateral angles. 
Devonian. 
Family 12. Ryticeratidae. 
Cyrtoceracones and gyroceracones resembling Halloceratidae, but much larger, with 
coarser crenulated bands, and often with rows of spout-like spinous processes which some- 
times form coarse longitudinal ridges. Siphunele more or less nummuloidal, and larger 
than in Halloceratidae. 
Ryticeras, Hvatt (Rutoceras, Hyatt), Cophinoceras, Strophiceras, Hyatt. Devonian. 
y d “ > J ’ b) J « 
V. MRHADINOCERATIDA. 
Cyrtoceracones, gyroceracones, and nautilicones having smooth or spinous longitudinal 
ridges in the young, which become large and fluted in some genera, but disappear in 
others, Ridges more or less sporadically combined with fold-like annulations, thus 
suggesting direct descent from the Kionoceratidae. 
large siphuncle close to the dorsum from an early stage onward, 
Sata ay 
