PHYSETERIDAZA 251 
been met with at various distant localities in the Southern Ocean, 
and also off the coast of Madras and in the North Pacific. 
Extinct Physeteroids.—Teeth of Physeteroids are of very common 
occurrence in the Belgian and English Crags, and evidently indicate 
the former existence of Whales more or less closely allied to the 
Sperm Whale, but often distinguished by the presence of an enamel- 
cap on the crowns of the teeth. The generic determination of these 
teeth is, however, exceedingly difficult, owing to the water-worn 
condition in which they are frequently found, and also on account 
of the impossibility of knowing whether small and large teeth may 
not be referable to different parts of the jaws of the same species 
or to individuals of different ages. Moreover, in the cases of 
isolated teeth it is impossible to know how many were contained 
in the jaws, and therefore to distinguish Physeteroid from Ziphioid 
teeth. Physeterula is a small form about one-third the dimensions 
of the Sperm Whale, and distinguished by the length of the mandib- 
ular symphysis being only about one-third that of the entire ramus ; 
it is identified by Professor Cope with Cogia. Eucetus (Dinoziphius) is 
founded on teeth which are regarded as closely resembling those of 
Physeter, but distinguished by their subcylindrical form and the 
small size of the aperture of the pulp-cavity. It does not appear, 
however, to be certain that these teeth are not worn specimens of 
those described as Scaldicetus. Physetodon, from the Pliocene of 
Australia, is founded upon the evidence of similar teeth. The teeth 
from the Belgian Crag described as Scaldicetus are somewhat smaller 
than those of the Sperm Whale, and are readily characterised by 
their cap of grooved enamel. Other teeth with enamel-caps have 
been described as Physodon and Hoplocetus. The genus Balcenodon 
is founded upon a very imperfect large tooth from the English Crag, 
which is not sufficiently well preserved to admit of exact comparison 
with the other types. 
Subfamily Ziphiinee.—Teeth of the mandible (at least in existing 
forms) quite rudimentary and concealed in the gum, except one, or 
very rarely two, pairs which may be largely developed, especially 
in the male sex. A distinct lachrymal bone. Externally the mouth 
is produced into a slender rostrum or beak, from above which the 
rounded eminence formed by a cushion of fat resting on the cranium 
in front of the blowhole rises somewhat abruptly. Spiracle or 
blowhole single, crescentic, median, as in the Delphinidw. Pectoral 
fin small, ovate, the five digits all moderately well developed. A 
small obtusely falcate dorsal fin situated considerably behind the 
middle of the back. Longitudinal grooves on each side of the skin 
of the throat, diverging posteriorly, and nearly meeting in front. 
In external characters and habits the animals of this group closely 
resemble each other. They appear to be almost exclusively feeders 
on various species of cephalopods, and occur either singly, in pairs, 
