566 CONCLUSIONS. 
1880, who was thereto invited by Aten, though this skilled 
zoologist was then unaware of the existence of the sea-serpent, or 
at least must have doubted its belonging to this branch. I have 
not a single reason to give another name to it; I purposely keep 
the name of Gressigrada, to avoid the increase of synonyms. The 
early forms of the Gressigrada must have had hind-legs which 
were smaller than the fore-legs, and a tail, which was as long as 
the head, neck and trunk together. They had also small external 
ears, and a somewhat lengthened neck. Further characters are: 
“Hind-legs capable of being turned forward and used in terrestrial 
locomotion. Neck lengthened (especially in section b). Skull with 
the mastoid processes large and salient (especially in the males), 
and with distinct alisphenoid canals. Anterior feet either nearly 
as large as the posterior, or much larger, their digits rapidly de- 
creasing in length from the first to the fifth, with distinct claws, 
and with a broad cartilaginous border extending beyond the digits.” 
(‘hey are called flappers.) “Hind-feet susceptible of great expansion, 
the three middle digits only with claws, and all the digits termin- 
ating in long, narrow, cartilaginous flaps, united basally.” (The 
hind-feet may also safely be called flappers.) “Femur with the 
trochanter minor well developed”’.— Already at a very early date 
the branch of the Gressigrada divided itself into two sections, 
which are marked below with a and b. — 
a.— The members of this section changed their manner of living. 
They very often crawled on ice, land, and rocks; the long tail 
was a very imconvenient organ in their new manner of living, 
consequently all the individuals with a somewhat shorter tail than 
their congeners’ were better equipped, and survived the others, so 
that at last a group of animals arose of which the tail has become 
very short, scarcely, if at all, visible, being enclosed within the 
tegument of the body, and to make up for this loss, the hind- 
flappers grew much larger than the fore-flappers. The further char- 
acters for this group are: “Without external ears. Form thick and 
heavy. Anterior portion of the skull greatly swollen, giving support 
to the enormously developed canines, which form long, protruding 
tusks. Incisors of deciduous (foetal) dentition ¢; of permanent 
dentition ¢. No postorbital processes, and the surface of the mastoid 
processes continuous with the auditory bullae.” — This section is 
called Z'richecidae by Gray in 1821 (afterwards it was named 
Trichechidae by Gray in 1825, Broca by Larruitie in 1825, 
Campodontia by Brooxrs in 1828, Trichecima by Gray in 1887, 
