Odontoid process of second vertebra semi-cylindrical; skull with a sagittal crest; and the condyle of the lower jaw rounded.
The latter is, in comparison with mammals, represented by its middle portion only, the vermis; in a sagittal section it shows an extremely well developed arbor vitae, produced by the transverse, repeated folding of the whole organ.
There is generally no sagittal crest to the skull; and the condyle of the lower jaw is transversely elongated.
The skull generally lacks a sagittal crest; and the condyle of the lower jaw is transversely elongated.
The first is a ventral flexure in the antero-posterior or sagittal plane; the result of this is to approximate the two ends of the alimentary canal.