922 
curvature of the spine, is natural, and not due 
to post-mortem disturbance. This curve is 
beautifully indicated hetween C. 30 and C. 
63; behind which the vertebre dip down 
into the extremity of the tail. It is diffi- 
cult to verify the existence of this curve in 
the living state by the measurement of the 
superior and inferior diameters of the cen- 
tra. So far as measurements can be relied 
upon they tend to show that the vertebral 
centra were slightly longer above than be- 
low and thus produced the curve; the re- 
lations of the greatly reduced zygapophyses 
and the antero-posterior width of the spines 
also point to the same conclusion, for they 
show that if this column were straightened 
out the spines would come into contact. 
This condition is so unique, however, that 
it must be put forward with reserve. 
The sharp ventral flexure or angulation 
of the tail of Iehthyosawrus, below the swell- 
ing of the caudal fin is not analogous to the 
very gradual upward curve in Tylosaurus. 
We are now enabled to form a very clear 
idea of the general structure of the thorax, 
although certain details-are still missing. 
All the true ribs are preserved on both sides, 
and, in spite of the hayoe wrought in the 
removal of the chest region, we find all but 
one of the cartilaginous ribs on the left side 
and extensive portions of those on the 
right, as well as the central area of the 
sternum. The careful studies and draw- 
ings of this region by Dr. J. H. McGregor 
show clearly the relations of the actual and 
restored region, part of the preserved region 
being covered by the vertebree and ribs. 
The cartilaginous ribs, consist of broad 
bands which are closely concentrated and 
parallel as they converge towards the sides 
of the sternum, affording an exceedingly 
strong support for the thorax. The floating 
ribs decrease steadily in length and curva- 
ture. The coracoids do not unite in the 
median line as represented by Marsh,nor are 
they approximated as restored by Dollo in 
SCIENCE. 
[N.S. Vou. X. No. 260. 
Plioplatecarpus. They are widely separated 
by epicoracoid cartilages having a united 
transverse diameter of about 22 centi- 
metres. The inner ends of the bony cora- 
coids are thus nearly nine inches apart. 
About one-half of the sternwm is visible or 
preserved ; as the cartilaginous ribs on tie 
left side are nearly in situ, and those on the 
right approximately so, it is evident that 
the sternum had a triangular outline, thin- 
ning posteriorly for the junction of the 10th 
pair of cartilaginous ribs. 
The sterno-coracoid plate thus corre- 
sponds closely with the Lacertilian type 
and bears a general resemblance to those of 
Trachydosaurus, Varanus and Cyelodus, as fig- 
ured by Parker. There is no evidence of the 
presence of an episternum (interclavicle ). 
Behind the basioccipital is observed a 
supposed lateral cartilage of the larynx ? lz. 
and its mate ? vz. appears below just between 
the right pterygoid and quadrate. A bit of 
cartilage appears behind the left quadrate, 
another mass in front of the right quadrate, 
while the trachea extends from below the 
axis, is unfortunately destroyed as far back 
as the 5th rib, and diverges into the two 
bronchi just behind the coracoids. The tra- 
cheal rings are well exhibited. 
The appendicular skeleton is remarkably 
well preserved. The scapule are fully ex- 
posed upon both sides, with the characteristic 
short and broad bony blades and the exten- 
sive crescentic cartilaginous suprascapule. 
COMMON CHARACTERS OF FORE AND 
HIND PADDLES. 
The metapodials and podials are some- 
what displaced, but they enable us to make 
a reconstruction of the manus, aided by 
Williston’s excellent photograph and out- 
line of the paddle in TY. proriger. 
1. Hyperphalangism is a chief character- 
istic of the Tylosaur extremities. Willis- 
ton’s photograph shows 47 actual elements, 
to which 3 are added in his restoration of 
