CONCLUSIONS, 565 
bone imperforate and joined to the maxillary, enclosed wholly 
within the orbit. Palatines usually separated by a vacuity, often 
of considerable size, from the frontals. Tympanic bones separated 
also by a vacuity from the exoccipitals. Dentition simple, generally 
unspecialized, the molars all similar in structure. Deciduous denti- 
tion rudimentary, never truly functional, and generally not persistent 
beyond the foetal stage of the animal. Permanent incisors usually 
+ or 4, sometimes + (Cystophora and Macrorhinus) or even } 
(Odobaenus); canines ?; molars ?, $, or #.” 
And we may add: Tail either very long: about as long as one 
half of the animal’s total length, or very short: almost disappear- 
ing between the hind-legs. 
Already very early the Pinnipeds divided themselves into two 
different branches, marked below with I and II. 
I. — The members of this branch changed their manner of lia 
They very often crawled on land, ice, and rocks; the long tail 
was a very unconvenient organ in their new manner of living, 
consequently all the individuals with a somewhat shorter tail than 
their congeners’ were better adapted to the new manner of living 
and survived them, so that at last a group of animals arose of 
which the tail has become very short, almost disappearing between 
the hind-legs, and to make up for this loss the hind-legs grew 
much larger than the fore-legs, were turned hindwards, gradually 
grew incapable of being turned forwards, and of no use in terres- 
trial locomotion. This branch is called Znauriculata by Pron in 
1816 (afterwards called Phocidae by Gray in 1825, and Reptigrada 
by Extior Covss, invited thereto by Atien in 1880). The char- 
acters are described by ALLEN as follows: 
“Hind-legs not capable of being turned forward, and not servi- 
ceable for terrestrial locomotion. Neck short. Skull with the mastoid 
processes swollen, but not salient, and without distinct alisphenoid 
canals. Anterior limbs smaller than the posterior, the first digit 
little, if any, longer than the next succeeding ones, all armed with 
strong claws, which are terminal. Hind feet capable of moderate 
expansion, short; digits (usually) all armed with strong claws, and 
without terminal cartilaginous flaps. Femur with no trace of the 
trochanter minor. Without external ears. Postorbital processes want- 
ing, or very small. Incisors variable (¢, +, or +). Deciduous den- 
tition not persistent beyond foetal life.” 
The group includes all true seals and sea-elephants. 
Il. — This branch is called Gressigrada by Exiiot Cours in 
