| 1.5 | 1.5 | 1.0 | 1.0
Terminal Phalanx B | 1.5 | 1.5 | 1.0 | 1.0
--------------------------+----------+----------+----------+----------

COMPARISONS AND DISCUSSION

Apparently primitive rhipidistian characters in _Hesperoherpeton_ are:
Braincase in two sections, posterior one containing an expanded
notochordal canal; lateral series of mandibular bones closely
resembling that of _Megalichthys_, as figured by Watson (1926); tabular
having long process probably articulating with pectoral girdle; lack of
movement between head and trunk correlated with absence of occipital
condyle; sensory pits present on frontal and squamosal.

Although we are unable to separate, by sutures, the vomers from the
palatines, the palatal surface of these bones and of the pterygoids is
studded by numerous small teeth, as in Rhipidistia (Jarvik, 1954) and
some of the early Amphibia (Romer, 1947). The stapes apparently reaches
the quadrate, and could therefore serve in hyostylic suspension of the
upper jaw.

The pectoral limb has an axial series of bones carrying hooklike
flanges on their posterior edges. The other bones of the limb show
little modification of form beyond the nearly flat, aquatic type seen
in Rhipidistia. No distinct elbow or wrist joints are developed.

Characters of _Hesperoherpeton_ common to most primitive Amphibia, in
contrast with Crossopterygii, are: Nares separated from edge of jaw;
stapes having external process that may have met a tympanic membrane,
thus giving the bone a sound-transmitting function. Apparently none of
the opercular series was present.

There are two large palatal teeth, slightly labyrinthine in character,
adjacent to each internal naris. The scapulocoracoid, as shown by
Peabody (1958), is Anthracosaurian in structure, as are the
long-stemmed clavicles. The limbs have digits rather than fin-lobes,
although the digital number apparently is four and the number of bones
in the manus is less than would be expected in a primitive amphibian.
The vertebrae are similar to those of Ichthyostegids, as described by
Jarvik (1952), except that the pleurocentra are much larger.

In addition to this remarkable combination of crossopterygian and
amphibian characters, _Hesperoherpeton_ is specialized in certain
features of the skull. The orbits are much enlarged, probably in
correlation with the diminutive size of the animal, and this has been
accompanied by loss o