The species _europæus_ differs from _bidens_ in the following characters,
which may be regarded as diagnostic:
Size larger and pectoral limbs relatively shorter and narrower.
The expanded portion of the maxillæ and frontals broader in front of the
orbit. The protuberance which projects into the anteorbital notch much
larger and the ridge on the maxilla which extends backward from it much
higher. Distance from inner margin of maxillary foramen to tip of
protuberance much more than one-half the distance between the maxillary
foramina of the two sides. Rostrum deeper at the base. Inferior surface
of pterygoids more or less convex, with a ridge (in adults) running
diagonally across it.
The cranial characters above enumerated are found in the type-skull, as
will be seen by examining the excellent figures in Van Beneden and
Gervais’ Osteography, plate 24.
In Dr. Glover M. Allen’s account of the Long Branch specimen[22] it is
stated that the fishermen who measured it reported that it was 22 feet
long, while none of the European specimens (some of which were certainly
adults) was more than 16½ feet long. That the measurement reported by the
fishermen is at least approximately correct appears from the fact that
the skull is larger than that of any of the European specimens. The beak
is missing, so that the total length of the skull can not be given, but
the distance from the occipital condyles to the line of the maxillary
notches (straight) is 312 mm., while in the largest adult among the
European specimens this distance is only 260 mm., and in the thoroughly
adult Nantucket specimen 282 mm.