Murrayoceras
Murrayoceras is a nautilid cephalopod included in the orthocerid family Baltoceratidae , widespread in the Middle Ordovician of North America , characterized by a depressed orthoconic shell with a subtriangular cross section and flattened venter and a proportionally large ventral siphuncle , 0 . 15 to 0 . 3 the dorso-ventral shell diameter . 
<triplet> Baltoceratidae <subj> orthocerid <obj> parent taxon