The San Francisco call., 1905-01-23
* NEWS OF THE COUNTY OF ALAMEDAeo
LIVED AGES BEFORE
THE SIERRAS ROSE.
Merrian's Saurians Shed Light
on Age Of the World.

material has made the problem more compli-
Gated.
We now know that there are four type Of
linabs--n1lxosaurus, toretocremus, shastasauruS
and Aiexapdrae. The fourth appears In a re-
Gently discovered specimen which seems to De
practically identical with shastasaurus per
rini-a genus disttnct-so we shall call IL DEL
phinosaurus. The mixosaurus e1trenities are
OF the primitive type. Those OF the deIphino,
saurus are characterized by much elongated
vertebral centra, unnotched scapula ana
humerus as broad it is long.
in which the limb structure is known BEDS
in which il occurs are considered by y1traas as
the equivalent of some portion OF the middle
trassic, while the California genera belong to
the upper triassic.
A comparison of the 3urassie and triassic
genera OF the ichthyosaur with view TO de-
termining the lines OF descent shows inmedi-
ately that no known 1urassic form can be con-
siderea as. having descended from the special
ized shastasaurus. SO far as we know THIS
group disappeared in the triassic
1t should be borne In mind that while the
evidence furnished by limb structure is some
of the most valuable material that we can OBJ
tain for use in working out the phylogeny OF
the ichthyosaur, 1t can hardly furnish the
whole Foundation for a definite classification
Inside the American group there seems to
be considerable variation. though as yet we
do not know all the most important charac-
II is perhaps a significant fact that Of the
several genera toretocremus. with the largest
vestigal fourth digit. appears in its general
structure to be nearest TO some OF the earlier
forms Of 1. Europe presented by ichthyosa1ir
atayas from the lower portion OF the middle
triassic.
The "Alexandrae" type referred to by
Professor Merriam was named by him
after Miss A. M. Alexander, of Oak
land. a young woman who has taken
part In Professor Merriam's expeditions
and herself has contributed notably to
some of the results attained on these
trips.
The significance of Professor Mer-
RAMS technical discussions of changes
in bone structure found in ichthyosaur
fossils may be better understood when
It is known, for example, that these
bone changes are coincident with the
ichthyosaur's development from
land-moving form to a reptile, or ami
NAL fitted for aquatic life. In such
transformation, which, Professor Os-
born says in his article before referred
to, would have delighted the eye of
Darwin, jointed limb gradually dis
solves into a fin composed Of f1attened
plates; the distinction between the
forearm, the wrist and the hand dis
appears; and numerous small addf-
tional Joints are added to the tips OF
the fingers 80 that instead Of the i've
Joints found in the longest finger or
the tuatera lizard as many as sixteen
Joints are finally developed on the mid
die finger of the ichthyosaur.
Some conception OF the enormous
length of the reign of the ichthyosaurs,
says Professor Merriam, quoting Os-
born, and Of the profound changes
which occurred in the North American
continent while 1t was progressing may
be had when 1t is known that when
the ichthyosaurs first took to the sea
the Appalachian chain Of mountains
was Just completing its upheayal;
while they were In the height of their
prosperity the Sierra Nevadas arose on
the western border of the continent;
while they were undergoing their de-
cline and approaching extinction the
Rocky mountain range and the region
of the great plains were rising from the
sea. The whole history Of their dis
persal on the high seas therefore took
place during a period roughly esti-
mated in our scale at eight millions Of
years.