T he Sua-ANGULAUv Bones, n. Tlie suv-angularies are placed at the supeiiov part of the posterior
third of the lower jaw and arc the thinnest of all that enter into its structure. Thoir edges are squamose;
and they have an anlcrior lengthened apaphysis.
CoJHie.rtoii. Before with the angular, opercular, and dental bones, and'witli the coronoids and
articulars behiiicl.
The ConoNoiD Bones, v. Tliese are very strong and have upon their superior part numerous
tubercles and depressions for the insertion of articular tendons. They are rounded and thick upon tlicir
outer and inner side, hollowed above from behind to before and dwindle into a short spinous apophysis,
whicli slopes downwards and forwards, anteriorly.
Connexion. Posteriorly with tlie articulars and before witli tlie sur-angulars.
The AnTicuLAR Bones, w. The articulars liave a concaoity superiorly, an inferior sharp ridge,
and an outer convex and an inner concave side. The superior concavity is divided into two portions, an
anterior one with its long axis from side to side and a posterior with its greatest diameter from before to
beliind. The outer convex side is roughened for the attachment of muscles.
Connexion, Anteriorly and superiorly with tiio coronoid and below with the angulars botli witliin
and without, and the sur-angiilars.
THE TEETH.
Upon the anterior half of tho maxillaries and the entire dental processes of the inter-maxillaries is
situated a deep sulcus for the teeth of the upper jaw which is bounded by an outer and inner edge. The
dental bones contain all the teeth which belong to the inferior jaw. These teeth are securely lodged in
deep cavities and separated by prominent ridges from one another ; they arc very long, slender and but
faintly striated upon their enamelled portion. Their root is round, smooth and invariably hollow. Like
the tcctli of Ichthyosauri they wore in a perpetual state of decay and reparation, and the re-institution
of tliem was effected in the same manner, that is, by tlie forcible extrusion of the old by the young.
From (he great number of foramina for nutritive vessels which mark the osseous nursery ivlicncc the new
teetli proceeded I presume that their groivtli and decay was rapid. Nor did the reproductive energy
diminish by age as regarded either the Plesiosauri or the Ichtliyosauri; in tlie inferior jaw of the
Plesiosaurus plate twenty-six, tlie reader will perceive tlie alveolar portions of two old teeth and in several
otiicr cavities the young ones wliich liaving loosened those tliey were intended to replace, caused them to
fall out of their several sockets as soon after the death of the animal as the decomposition of the soft parts
was effected. The teeth varied in number according to the species and the age of the individual: they
amounted to nearly seventy in the inferior jaw, and from seventy to ninetj- in the superior.
THE LARGE CAVITIES IN THE HEAD.
I. The nasal foramina placed just before the orbits are extremely small: They are formed above
by the nasal bones and below by the inter-maxillaries. They are rounded and situate at the inferior part
of the upper third of tlie short diameter of the jaw,
II. The maxillaries, inter-maxillaries and anterior process of the posterior frontals compose the
upper and tlie fore part of the orbits. Tlieir liindcr region is bounded by the posterior frontals and tlieir
inferior by the jugals, tlie splienoid assists to divide tliom one from the other internally. We have not
found sclerotic plates as yet but do not doubt but Plesiosauri had them.
III. Tlie temporal fossæ are gigantic; they a re .bounded above by the parietalia, below by the
temporals, before l>y the posterior frontals and behind by the temporalia and parietal bones.
IV. The occipital foramen is very small and is effected by the superior, inferior and lateral occipital
TH E TRUNK.
THE SPINAL COLUMN.
1 y
n
jhty-five boi titiite tlie spinal column, eacli of whicli has a body, a bony arch, certain
upon their inferior concave portion. As processes and iwo foramh these characters vary in different
places it is necessary to describe the bones under the names cervical, dorsal and caudal.
T he Cervical Vertebræ. The atlas and dentatus differ from the other cervical vertebræ in having
no hatchet-likc processes or small cervical bones for the attaclimcnt of muscles ami protection to tlie
intei-vertobral arteries. Moreover the atlas has an anterior convex articular face upon wliich the head
rotated and a posterior flat one which was united by a synartlirodial junction to tlio dentatus, wliile tlic
other vertebræ have two sides without slightly concave and witliin slightly convex. The body is the
most round of all tliosc of the bones of this truly magnillcent neck. Its bony arch is strong and
common to it and the dentatus wliich is a mere flattened piece of bone. Tho spinous apophysis, with its
posterior articular body, is smaller tlian those which follow it.
Tlic hatchet-like processes, so leraarkable in long-ncckcd quadrupeds and birds, distinguish the
remaining thirty vertebræ of the neck of the Plesiosaurus; they increase in size as they proceed
backwards. The stprocesses arc Erinly fixed into a socket at the middle of each side of the vertebræ,
from which they proceed forwai-ds and terminate in a point. They are convex inferiorly and tlicir
posterior extremity touches the anterior part of the succeeding one. In the Plesiosaurus plate twenty-
five, which was discovered at Walton, these processes are metamorphosed into a kind of false rib as they
approacli tlio dorsum.
The articular bodies of these cervical vertebræ, joined to the body like those of crocodiles, as ai c all
the articular bodies of the other vertebræ, are concave at tlieir external (liird, witliin that tlicy become
conve.x. The bony arch for the passage of the spinal chord is Jai^e and tlie apophysis, wliicli exceeds
in length the long diameter of the vertebra to wliicli it is attached, has two advancing articular processes
bcfoi'c and two posterior ones which necessarily overlap tlic next following. Above tlie spinous apophysis
is convex and grooved for the cervical ligament.
T he Dorsal Vertebræ. These are twenty in number and differ from the cervical in being larger
in every particular; in being more concave at their sides and flatter at their ar/iciiZac siir/flccs and in
having on each side of tlieir bony arch a large transverse process for tlic articulation of the ribs. This
transverse process is rounded inferiorly and stretches outwards and backward into a large knobbed
extremity with its head concave and roughened. The under surfaces of tlie dorsal vertebræ are slightly
flattened when compared with their sides and their spinous apophyses are longer and wider than tliose of
the neck.
T he Caudal Vertebræ. The caudal vertebræ, commencing immediately behind (he pelvis, are
known from ail the others by tiieir transverse and lateral processes and by their more concave articular
extremities. They amount to tliirty-tlirce and have transverse apophyses willi aniuilar articulations
which are straight and independent of each other. Their chevron or lateral processes articulate in a
fossæ upon each side of their inferior body, are longer than tlic transverse and end in a sharp point.
Tlie last three or four vertebræ possess neither transverse nor lateral articulare.
THE STERNUM.
Tlio sternum is a tliin bone, hollowed within from side to side; liaving an anterior concave p/orlion,
two lateral articulatory surfaces for attachment lo the clavicles and a posterior articulation with tlic
scapula’s which is raised into a sharp median ridge externally. That gigantic sternum in plate twenty-
six was found with the inferior jaw, before noticed, at Mareh’s Elm in the parish of Street in 31. It
announces an individual more than twenty feet long; but I have part of a humerus from Whitby of a
Plesiosaurus that was forty feet.