The shell of " Uranoceras " is typically smooth but may have growth lines that form a hyponomic sinus on the venter.
12.
The aperture as vertically transverse, with a hyponomic sinus on a low spout-like process and a larger rounded dorsal sinus connetected above.
13.
The shell of " Neoaganides " has a well-developed hyponomic sinus and shallow lateral reentrents at the aperture outlined by growth lines.
14.
A principal character is the slit-like aperture with a hyponomic sinus for the water-jet funnel, and mid dorsal and dorsolateral sinuses.
15.
Aperture contracted and visored with a long ventral hyponomic sinus, 2 pairs of shorter dorsolateral sinuses, and a short dorsal salient branching from the peristome.
16.
Ornamentation consists of a series of spines on either side as well as transverse straie which form a well developed hyponomic sinus ( for the funnel ) on the venter.
17.
""'Lyecoceras " "'is a slender endogastrically curved orthocerid, so determined by identification of the hyponomic sinus on the concave side.
18.
The more advanced and slightly later Madiganella may have been a fair swimmer, as indicated by the hyponomic sinus, and may have been an active stalker with a horizontal orientation.
19.
Aperture unconstricted with no hyponomic sinus for the water jet funnel . siphuncle along the outer, ventral, side, with radial, plate-like actinosiphonate deposits occupying the interior.
20.
The shell is encircled periodically by crenulate frills, each of which is bent apically so as for form a well defined hyponomic sinus, but are without spoutlike or spinose projections.
