AN INTRODUCTION

TO THE

OSTEOLOGY OF THE MAMMALIA.

AN INTRODUCTION

OSTEOLOGY OF THE MAMMALIA

WILLIAM HENRY FLOWER, LL.D., F.R.S.

DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM

LATH HUNTERIAN PROFESSOR OF COMPARATIVE ANATOMY AND PHYSIOLOGY

IN Till: ROYAL COLLEGE OF SURGEONS OF ENGLAND.

WITH NUMEROUS ILLUSTRATIONS.
THIRD EDITION

REVISED WITH THE ASSISTANCE OF

HANS GADOW, Ph.D., M.A.

LECTURER ON THE ADVANCED MORPHOLOGY OF VERTEBRATES AND STRICKLAND CURATOR
IN THF. UNIVERSITY OF CAMBRIDGE.

Bonbon :

MACMILLAN AND CO.
1885

[The Righl of Translation and Reproduction is Reserved.}

RICHARD CLAY AND SONS,

ItKEAD STREET HILL, LONDON, E.C.

Ami Bnngay, Suffolk.

PREFACE.

THE desire to acquire a knowledge of the structure of some
portion at least of the Animal Kingdom, now becoming so
general, is often checked by the difficulty of determining
where to make a beginning amid the vast extent and variety
of the materials at hard.

I have selected for my first course of lectures on Com-
parative Anatomy at the Royal College of Surgeons, the
structure and modifications of the Skeleton, because, as
the framework around which jthe rest of the body is built
up, it gives, more than any other system, an outline of the
general organization of the whole animal, and also because
it is the most convenient for study, on account of the
facility with which it can be preserved and examined.

Moreover, Osteology has special importance in com
parison with the study of any other system, inasmuch as
large numbers of animals, all in fact of those not at presen
existing on the earth, can be known to us by little else than
the form of their bones.

In endeavouring to gain anatomical knowledge, it sig-
nifies little with which group of animals a commencement
is made.

20542OS

vi PREFACE.

The structure of Man has undoubtedly a more universal
interest than that of any other organized being, and
has, therefore, been more thoroughly worked out ; and as
the majority of terms used in describing the parts com-
posing the bodies of Vertebrate animals were originally
bestowed on account of their form, relation, or real or
fancied resemblance to some object, as they were met
with in Man, there are advantages in commencing with
members of the highest class, and mastering their essential
characters before proceeding to acquire knowledge of the
other groups.

But as human anatomy may be taken as a point of de-
parture from which to set out in the study of that of other
Vertebrates, so, on the other hand, those whose special
duty it is to become familiar with its details, will find
themselves greatly assisted by some knowledge of the
structure of lower forms. Thus the essential characters
of the human skull will be much better understood if the
student will also make himself acquainted with those of
some simpler condition of Mammalian cranium, as that of
the dog or sheep.

Although the present work contains the substance of a
course of lectures, the form has been changed, so as the
better to adapt it as a handbook for students. Theoretical
views have been almost entirely excluded ; and while it is
impossible in a scientific treatise to avoid the employment
of technical terms, it has been my endeavour to use no
more than are absolutely necessary, and to exercise due
care in selecting only those that seem most appropriate, or
which have received the sanction of general adoption.

PREFACE. vii

With very few exceptions, all the illustrations have been
drawn expressly for this work, with great care and fidelity,
by Mr. R. W. Sherwin, from specimens in the Museum of
the Royal College of Surgeons.

September 2^1 ft, 1870.

NOTE TO THE THIRD EDITION.

This edition has been revised throughout. Several new
illustrations, a table shewing the number of the vertebra?
of a large number of species, and many references to the
more important recent memoirs on the subjects referred
to, have been introduced.

Odobtr ist, 1885.

CONTENTS.

CHAPTER I.

PACK
CLASSIFICATION OF THF. MAMMALIA . I

CHAPTER II.
THE SKF.LETON 12

CHAPTER III.

THE VERTEBRAL COLUMN 1 5

CHAPTER IV.

SPECIAL CHARACTERS OK THE CERVICAL VERTEBR/E IN THE

MAMMALIA J2

CHAPTER V.

SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR VER-
TEBRA 51

CHAPTER VI.

SPECIAL CHARACTERS OF THE SACRAL AND CAUDAL VER-
TEBRA 66

CONTENTS.

CHAPTER VII.

PARK

THE STERNUM 9°

CHAPTER VIII.

THE RIBS 1 06

CHAPTER IX.

THE SKULL OF THE DOG Il6

CHAPTER X.

HIE SKULL IN THE ORDERS PRIMATES, CARNIVORA, INSECTI-

VORA, CHIROPTERA, AND RODENTIA 150

CHAPTER XI.

THE SKULL IN THE UNGULATA, HYRACOIDEA, AND PRO-

BOSCIDEA 185

CHAPTER XII.

THE SKULL IN THE CETAr:EA AND THE SIRENIA 209

CHAPTER XIII.

THE SKULL IN THE EDENTATA, MARSUPIALIA, AND MONO-

TREMATA 22Q

CHAPTER XIV.

THE SHOULDER GIRDLE 243

CONTENTS.

CHAPTER XV.

PACK

THE ARM AND FORE-ARM . . . 266

CHAPTER XVI.
THE MANUS .280

CHAPTER XVII.

THE PELVIC GIRDLE 312

CHAPTER XVIII.
THE THIGH AND LEG -*

CHAPTER XIX.

THE HIND FOOT OR PF.S 338

CHAPTER XX.

THE CORRESPONDENCE BETWEEN THE BONES OF THE ANTE-
RIOR AND POSTERIOR EXTREMITY AND THE MODIFICA-
TIONS OF THE POSITIONS OF THE LIMBS 361

INDEX 375

AN INTRODUCTION

TO THE

OSTEOLOGY OF THE MAMMALIA.

CHAPTER I.

CLASSIFICATION OF THE MAMMALIA.

IT is not the object of the present work to enter in
detail into the subject of the Classification of the Mam-
malia ; but, as it will be necessary to refer frequently to the
principal subdivisions in which the various animals treated
of are arranged, a brief outline of the system adopted will be
necessary.

A perfect arrangement of any group of animals can only
be attained simultaneously with a perfect knowledge of their
structure and life-history. We are still so far from this
that any classification now advanced must be regarded as
provisional, and merely representing our present state of
knowledge. Moreover, as naturalists will estimate differ-
ently the importance to be attached to different structural
modifications as indicative of affinity, it must be long before
there will be any general agreement upon this subject

2 CLASSIFICATION OF THE MAMMALIA. [CHAP.

The classification and the names of the subdivisions used
throughout this work correspond, in the main, with those
given by Professor Huxley in his " Introduction to the
Classification of Animals," 1869.

The modifications of this classification which appear to be
necessitated by more recent acquisitions of knowledge will
be found fully detailed in the author's article, Mammalia,
in the ninth edition of the Encyclopaedia Britannica, vol. xv.
(1883), from which the following introductory observations
are extracted : —

One of the most certain and fundamental points in the
classification of the Mammalia is that all the animals now
composing the class can be grouped primarily in three-
natural divisions, which, presenting very marked differen-
tiating characters and having no existing — or yet certainly
demonstrated extinct — intermediate or transitional forms, may
be considered as sub-classes of equal value, taxonomically
speaking, though very different in the numbers and import-
ance of the animals at present composing them.

These three groups are often called by the names
originally proposed for them by De Blainville : (i) Or-
nithodelphia, (2) Didclphia, (3) Monodelphia^ — the first being
equivalent to the order Monotremata, the second to the
Marsupialia, and the third including all the remaining
members of the class. Although actual palseontological
proof is wanting, there is much reason to believe that each
of these, as now existing, are survivors of distinct branches,
to which the earliest forms of Mammals have successively
given rise, and for which hypothetical branches or stages
Huxley has proposed the names of Prototheria, Metatheria,
and Eutheria}-

I. The characters of the Ornithodelphia or Prototheria
1 Proceedings of the Zoological Society, 1880, p. 649.

i.] ORNITHODELPHIA. 3

can only be deduced from the two existing families, as
hitherto no extinct animals which can be referred to other
divisions of this remarkable and well-characterised group
have been discovered. These two isolated forms, in many
respects dissimilar, yet having numerous common characters,
which unite them together and distinguish them from the
rest of the Mammalia, are the Ornithorhynchida and the
Echidnidie, both restricted in their geographical range to the
Australian region of the globe. Taken altogether they
represent the lowest known type of evolution of the Mam-
malian class, and most of the characters in which they differ
from the other two sub-classes, tend to connect them with
the inferior vertebrates, the Sauropsida and Amphibia ,
for though the name Ornithodelphia owes its origin to the
resemblance of the structure of the female reproductive
organs to those of birds, there is nothing especially bird-like
about them.

Their principal distinctive characters are these : The
brain has a very large anterior commissure, and a very small
corpus callosum, agreeing exactly in this respect with the
next group. The cerebral hemispheres, in Echidna at least,
are well developed and convoluted on the surface. The
auditory ossicles present a low grade of development, the
malleus being very large, the incus small, and the stapes
columelliform. They have no true teeth, though the jaws
of Ornithorhynchns are provided with horny productions,
which functionally supply their place. The coracoid bone
is complete and articulates with the sternum, and there is a
large " interclavicle " or episternum in front of the sternum
and connecting it with the clavicles. There are also
"epipubic" bones. The oviducts (not differentiated into
uterine and Fallopian portions) are completely distinct, and
open as in other oviparous vertebrates separately into a cloacal

4 CLASSIFICATION OF THE MAMMALIA. [CHAT.

chamber, and there is no distinct vagina. The testes of the
male are abdominal in position throughout life, and the vasa
deferentia open into the cloaca, not into a distinct urethral
passage. The penis, attached to the ventral wall of the
cloaca, is perforated by a canal in the greater part of its
length, but not at the base, which is open, as in reptiles and
those birds which have such an organ, and brought only
temporarily in contact with the termination of the vasa
deferentia, so as to form a seminal urethra when required,
but never transmits the urinary secretion. This condition
is a distinct advance on that of the Sauropsida in the
direction of the more complete development of these
parts in most of the other Mammalia. The ureters do not
open into the bladder, but behind it in the dorsal wall of
the genito-urinary passage. The mammary glands have
no distinct nipple, but pour out their secretion through
numerous apertures in the skin ; the whole mammary area
is restricted to a slightly cup-shaped invagination of the
abdominal skin, forming a mammary marsupium, especially
developed in the females during lactation, but hardly recog-
nisable in the males. The Monotremata lay eggs and hatch
them in the abdominal pouch. The primary egg undergoes
meroblastic segmentation as in the Sauropsida ; the early
stages of the development of the young are not yet fully
known, but they appear never to be nourished by means of
an allantoic placenta.

II. The Didelphia, Marsupialia, or Metatheria are repre-
sented at present by numerous species, presenting great
diversities of general appearance, structure, and habits, al-
though all united by many essential anatomical and physio-
logical characters, which, taken altogether, give them an inter-
mediate position between the Prototheria and Eutheria. In
the structure of the brain and the presence of epipubic bones

I.] DIDELPHIA. 5

they agree with the former, while in the structure of the
earbones and the shoulder-girdle, and the presence of
true teeth, and of teats on the mammary glands, they
resemble the latter; the reproductive organs belonging to
neither one nor the other type, but presenting a special
character representing an intermediate grade of development.
The ureters open into the base of the bladder. The
oviducts are differentiated into uterine and Fallopian por-
tions, and open into a long and distinct vagina, quite-
separate from the cystic urethra. The penis is large, but
its crura are not directly attached to the ischia. The
spongy body has a large bifurcated bulb. The young are
born in an exceedingly rudimentary condition, and are
never nourished by means of an allantoic placenta, but are
transferred to the nipple of the mother, to which they remain
firmly attached for a considerable time, nourished by the milk
injected into the mouth by compression of the muscle cover-
ing the mammary gland. They are, therefore, the most
typically mammalian of the whole class. The nipples are
nearly always concealed in a fold of the abdominal integu-
ment or "pouch" (marsupium), which serves to support
and protect the young in their early helpless condition.
The existing species of this group are entirely confined to
the Australian region and the American continent, though
in former times they had a more extended geographical
range. The earliest Mammals hitherto discovered appear
(as far as the scanty evidence at present obtainable permits
any such conclusion to be hazarded) to have belonged to
this type, although it is reasonable to conclude that
Prototheria (unless upon the improbable supposition that
the existing forms have resulted from a process of degrada-
tion), and perhaps Eutheria, were their contemporaries far
back in the Mesozoic age.

6 CLASSIFICATION OF THE MAMMALIA. [CHAP.

III. The Monodelphia, Eutheria, or "placental mammals "
(so-called because the foetus is always nourished while
within the uterus of the mother by means of an allantoic
placenta), include at present by far the greater portion of
the class. While the survivors of the other groups have
probably been for a long time in a stationary condition,
these have, as there is already good evidence to show
throughout all the Tertiary geological age, and by inference
for some time before, been multiplying in numbers and
variations of form, and attaining higher stages of develop-
ment and specialisation in various directions. They con-
sequently exhibit far greater diversity of external or adaptive
modification than is met in either of the other sub-classes
— some being fitted to live exclusively in the water as
fishes, and others to emulate the aerial flight of birds.

To facilitate the study of the different component members
of this large group it is usual to separate them into certain
divisions which are called "orders." In the main zoologists
are now of accord as to the general number and limits of
these divisions among the existing forms, but the affinities
and relationships of the orders to one another are far from
being understood, and there are very many extinct forms
already discovered which do not fit at all satisfactorily into
any of the orders as commonly defined.

Commencing with the most easily distinguished, we may
first separate a group called Edentata, composed of several
very distinct forms — the Sloths, Anteaters, and Armadillos —
which under great modifications of characters, of limbs, and
digestive organs, as well as habits of life, have just enough
in common to make it probable that they are the very
specialised survivors of an ancient group, most of the
members of which are extinct, but which the researches of
palaeontology have not yet revealed to us. The characters

I.] MONODELPHIA. 7

of their cerebral, dental, and in many cases of their repro-
ductive organs show an inferior grade of organisation to thai
of the generality of the sub-class. The next order, about
the limits of which there is no difficulty, is the Sirenia —
aquatic vegetable-eating animals, with complete absence of
hind limbs, and low cerebral organisation — represented in our
present state of knowledge by but two existing genera, the
Dugongs and Manatees, and by a few extinct forms which,
though approaching a more generalised Mammalian type,
show no special characters allying them to any of the other
orders.

Another equally well marked and equally isolated, though
far more numerously represented and diversified, order is
that of the Cetacca, composed of the various forms of
Whales, Dolphins, and Porpoises. In aquatic habits,
external fish-like form and absence of hind limbs, they
resemble the last, though in all other characters they are
as widely removed from them as from any other order
among the Monodelphia. The association by systematists
of the Cetacea and Sirenia in our group can only be made
either in ignorance of their true structure, or in an avowedly
artificial system.

All the remaining orders are more nearly allied together,
the steps by which they have become modified from one
general type being, in most cases, not difficult to realise.
Their dentition especially, however diversified in detail*
always responds to some modification of the well-known
formula — incisors %, canines |, premolars *, molars £. Al-
though the existing forms are broken up into groups, in
most cases easy of definition, the discoveries already made
in palaeontology have in great measure filled up the gaps
between them.

Very isolated among existing Monodelphia are the two

8 CLASSIFICATION OF THE MAMMALIA. [CHAP.

species of elephants, constituting the group called Proboscidea,
These, however, are now known to be the survivors of a large
series of similar animals — Mammoths, Mastodons, and Dino-
theria — which as we pass backwards in time gradually assume
a more ordinary or generalised type ; and the interval which
was lately supposed to exist between even these and the
rest of the class is partially bridged over by the discovery
in American Eocene and early Miocene formations of the
gigantic Dinocerata, evidently offshoots of the great group
of hoofed animals or Ungtilata, represented in the actual
fauna by the Horses, Rhinoceroses, Tapirs, Swine, and
Ruminants.

Almost as isolated as the Proboscidea among existing
Mammals are the few small species constituting the genus
Hyrax, and in their case palaeontology affords no help at
present, and therefore, pending further discoveries, it has
been thought advisable in most recent systems to give them
the honour of an order to themselves under the name of
Hyracoidea. But the number of extinct forms already
known allied to the Ungulata, but not coming under the
definition of either of the two groups (Artiodactyla and
Perissodactyla) under which all existing species range them-
selves, is so great that either many new orders must be
made for their reception or the definition of the old order
Ungulata so far extended as to receive them all, in which
case both Proboscidea and Hyracoidea might be included
within it.

Again, the Rodentia or gnawing animals — Rabbits, Rats,
Squirrels, Porcupines, Beavers, &c. — are, if we look only at
the present state of the class, most isolated. No one can
doubt what is meant by a rodent animal, or have any
difficulty about defining it clearly, at least by its dental
characters ; yet our definitions break down before the

I.] MONODELPHIA. „

extinct South American Mesotherium, half Rodent and half
Ungulate, which leads by an easy transition to the still
more truly Ungulate Toxodon, for the reception of which a
distinct order ( Toxodontia) has been proposed.

The Insectivora and the Carnivora again are at present
quite distinct orders, but they merge into one another
through fossil forms, and are especially connected by the
large group of primitive Carnirora, so abundantly repre-
sented in the Eocene deposits both of America and Europe,
to which Cope has given the name of Crcodonta. The
transition from the Insectivora to the Lemurs is not great,
and, strange to say, however different they now appear, the
early forms of Lemurs are not easily distinguished from the
primitive Ungulata. The Hats or Chiroptera are allied to
the Insectivora in all characters but the extraordinary
modification of their anterior extremities into wings ; but
this, like the want of the hind limbs in the Cetacea and
Sirenia, makes such a clear distinction between them and
all other Mammals, that, in the absence of any knowledge
of intermediate or transitional forms, they can be perfectly
separated, constituting as well-defined an order as any in
the class.

Lastly, we have the important and well-characterised
group called Primates, including all the Monkeys and Man,
and the question is not yet solved as to how, and through
what forms, it is linked on to the other groups. It is com-
monly assumed that the Lemurs are nothing more than
inferior Primates, but the interval between them in the
actual fauna of the world is very great, and our knowledge
of numerous extinct species recently discovered in America,
said to be intermediate in character, is not yet sufficiently
perfect to enable us to form a definite opinion upon the
subject

io CLASSIFICATION OF THE MAMMALIA. [CHAP. i.

The accompanying diagram (page n) is intended to
exhibit the relationships which appear to exist between the
different groups of recent Mammalia. If all known extinct
forms were inserted, many of the intervals between the
boundary lines of the groups would be filled up ; other-
wise no great modification would be required in their relative
position. But our knowledge of the systematic position
and relations of the past forms of Mammalian life is in
general so imperfect and fragmentary, that it seemed best
to confine the diagram to a representation of the present
condition of Mammalian life upon the earth.

a

CHAPTER II.

THE SKELETON.

THE term Skeleton, in its widest sense, is used to denote
a system of hard parts forming a framework which supports
or protects the softer organs and tissues of the body, and
which may be either entirely external or superficial as
regards those organs and tissues, or may be more or less
embedded in enveloping softer structures. In the former
case it is called an Exoskdeton, in the latter an Endoskeleton.

It is of the Endoskeleton alone that this work proposes
to treat, as in the class Mammalia the external skeleton,
when it exists, performs a relatively subordinate part in the
economy.1

The branch of anatomy called Osteology is commonly
restricted to a study of such parts of the endoskeleton as
are composed of bony or osseous tissue, a tissue charac-
terised by a peculiar histological structure and chemical
composition, being formed mainly of a gelatinous basis,
strongly impregnated with calcium phosphates and car-
bonates, and disposed in a definite manner, containing
numerous minute nucleated spaces or cavities called
lacuna, connected together by delicate channels called
canaliculi, which radiate in all directions from the sides

1 The Armadillos and their extinct allies are the only known mam-
mals which have an ossified exoskeleton.

CHAP, ii.] THE SKELETON. 13

of the lacunae. This structure is readily recognised when a
thin section of bone is examined under a moderately high
magnifying power.

Parts composed of bone are, of all the tissues of the body
(with the exception of the teeth), the most imperishable,
often retaining their exact form and intimate structure ages
after every trace of all other portions of the organisation has
completely disappeared ; and thus in the case of extinct
animals affording the only means of attaining a knowledge
of their characters and affinities.

It must, however, be remembered that, at one period of
life, the parts composing the skeleton exist in a fibrous or
a cartilaginous form, that their transformation into bone is
a subsequent and gradual process, and that even in the
Mammalia, though in a less degree than in some of the other
Vertebrata, the whole of the internal skeletal system is
never entirely osseous, but that portions may remain per-
manently in a cartilaginous or fibrous condition.

The different bones composing the skeleton are con
nected together either by sutures, or by movable joints
or articulations.

In the first, the edges of the bones are in close contact,
often interlocking by means of projections of one bone
fitting into corresponding depressions of the other, and are
held together by the periosteum, or fibrous membrane in-
vesting the bones, passing directly from one to the other,
permitting no motion, beyond, perhaps, a slight yielding to
external pressure. The bones of the cranium are connected
together in this manner. In old animals there is a great
tendency for such bones to become joined together by
the extension of ossification from one to the other and
consequent obliteration of the suture. This process is
called synostosis.

14 THE SKELETON. CHAP. n.

The various forms of joints may be arranged under two
principal heads. In one, the contiguous surfaces of the
bones are connected by interposed fibrous tissue, passing
directly from one to the other, filling up the space between
them, and allowing of only a limited amount of motion, as
is the case with the bodies of the vertebrae.

The other and more frequent and more perfect form of
joint is that in which the contiguous extremities of the bones
are covered by a thin layer of very smooth cartilage, and
surrounded by a capsular ligament, attached only round the
edges of the articular surfaces, and which is lined by a
synorial membrane, so called from its secreting a viscid
lubricating fluid termed synovia. The amount of motion
permitted in these " synovial joints " varies according to the
form of the opposed articular surfaces and the arrangement
of the ligaments which hold them together. When the two
surfaces are nearly flat, and the bones firmly bound by strong
short ligaments, as in those which compose the carpus and
tarsus, the motion is reduced to an extremely slight gliding
of one on the other. Joints in the form of a hinge, as at
the elbow, allow of a free motion in one plane only. Ball
and socket joints, as at the shoulder and hip, allow of the
greatest variety of movements.

The Endoskeleton is divided into an axial portion, be-
longing to the head and trunk, and an appcndicular portion,
belonging to the limbs. There are also certain bones called
splanchnic, being developed within the substance of some of
the viscera. Such are the os cordis and os penis found in
some Mammals. These, however, are more appropriately
treated of with the anatomy of the organs of which they
form a part.

The Axial Skeleton consists of the vertebral column, the
skull, the sternum, and the ribs.

CHAPTER III.

THE VERTEBRAL COLUMN.

General Characters. — The Vertebral Column consists of a
series of distinct bones called Vertebra, arranged in close-
connection with each other along the dorsal side of the neck
and trunk, and in the median line. It is generally prolonged
posteriorly beyond the trunk to form the axial support of the
appendage called the tail. Anteriorly it is articulated with
the occipital region of the skull.1

The number of distinct bones of which the vertebral
column is composed varies greatly among the Mammalia,
the main variation being due to the elongation or otherwise
of the tail. Apart from this, in most Mammals, the number
is not far from thirty, though it may fall as low as twenty-
six (as in some Bats) or rise as high as forty (ffyrax and
C/wlaapus}.*

The different vertebrae, with some exceptions, remain
through life quite distinct from each other, though closely
connected by means of fibrous structures which allow of a
certain, but limited, amount of motion between them.

1 For the sake of uniformity, in all the following descriptions of the
vertebral column, the long axis of the body is supposed to be in the
horizontal position.

8 These numbers are not exact, owing to the uncertainty in the mode
of reckoning the sacral vertebrae.

1 6 THE VERTEBRAL COLUMN. [CHAP.

The exceptions are : Near the posterior part of the trunk,
in nearly all Mammals which possess completely developed
hinder limbs, two or more vertebrae become ankylosed
together to form the " sacrum," the portion of the vertebral
column to which the pelvic girdle is attached. As a rule,
none of the other vertebrae are normally united by bone,
but in some species there are constant ossific unions of
certain vertebrae, more particularly in the region of the
neck. These will be specially noticed presently.

FIG. 2. — Anterior surface of human thoracic vertebra^fourth), §. c body or centrum ;
«r neural canal ; / pedicle and / lamina of the arch ; / transverse process ; az
anterior zygapophysis.

Although the vertebrae of different regions of the column
of the same animal, or of different animals, present great
diversities of form, there is a certain general resemblance
among them, or a common plan on which they are con-
structed, which is more or less modified by alteration of
form or proportions, or by the superaddition or suppression
of parts to fit them to fulfil their special purpose in the
economy.

An ordinary vertebra (see Fig. 2) consists in the first place
of a solid piece of bone, the body or centrum (c), of the

in] GENERAL CHARACTERS. 17

form of a disk or short cylinder. The bodies of contiguous
vertebras are connected together by a very dense, tough, and
elastic fibrous material, called the interverttbral substance, of
peculiar and complex arrangement. This substance forms
the main, and in some cases the only, union between the
vertebrae. Its elasticity provides for the vertebrae always
returning to their normal relation to each other and to the
column generally, when they have been disturbed therefrom
by muscular action.

A process (/) rises on each side from the dorsal surface
of the body. These meeting in the middle line above form
together an arch, surrounding a space or short canal (tic).
As in this space lies the posterior prolongation of the great
cerebro-spinal nervous axis, or spinal cord, it is called the
neural canal, and the arch is called the neural arch, in con-
tradistinction to another arch on the ventral surface of the
body of the vertebra, called the hcetnal arch.1 The last is,
however, never formed in Mammals by any part of the
vertebra itself, but only by certain bones, placed more or
less in apposition with it, and which will not here be con-
sidered as parts of the vertebral column, strictly speaking.

The lower portions of each side of the arch (/>), usually
thick and more or less vertical in direction, constitute its
pedicles. The upper more compressed and more horizontal
portions (/) are the lamina. The pedicles are usually
notched in front and behind, but most deeply behind, to
form the sides of the interrertebral foramina for the trans-
mission of the nerves issuing from the spinal cord. Occa-
sionally the foramina for these nerves perforate the pedicles,
instead of being truly intervertebral.

The laminae meet in the median line above, at a more or

1 So called because it incloses the heart and the great central blood-
vessels

1 8 THE VERTEBRAL COLUMN. [CHAP.

less open angle. At the point of their junction there is
usually a single median process projecting dorsally, called
the spinous process or neural spine.

In most cases upon the anterior and posterior edges of the
laminae of the arch are flattened, slightly projecting, more or
less oval, smooth surfaces or facets, which in the natural state
are covered by a thin layer of cartilage, and come into
contact and articulate (by synovial joints) with the corre-
sponding surfaces of the immediately antecedent and suc-
ceeding vertebra?. These have been called by Sir Richard
Owen zygapophyses ; that placed on the front edge of the
arch being the anterior zygafophysis, that on the hinder
edge the posterior zygapophysis. As a general rule the latter
have their faces directed downwards, overlying the upward
directed anterior zygapophyses of the vertebra next behind.
This is a useful rule to remember in ascertaining which is
the front and which the posterior surface of a vertebra.
Sometimes, especially in the lumbar region, the posterior
zygapophyses have their faces directed outwards, in which
case the corresponding anterior zygapophyses look inwards
(Fig. 3, az).

These articular surfaces on the arch constitute a second
mode by which the vertebrae are united, and their size and
conformation aid to regulate the amount of motion allowed
between the component parts of the column. They are often
entirely wanting when flexibility is more needed than
strength, as in the greater part of the caudal region of
long-tailed animals.

In addition to the body and the arch, there are certain
projecting parts called processes, more or less developed in
different vertebrae. Many difficulties exist about the signi-
fication, homologies, and terminology of these processes.
Probably, when more is known of the development of the

in.] GENERAL CHARACTERS. 19

vertebrae in a large series of animals, some further light will
be thrown on the subject ; but at present it does not appear
that there is that uniformity in the plan of construction of
all vertebne which has often been supposed, and definitions
of the different parts applicable in every case have not yet
been arrived at, and it may even be doubted whether this
will ever be possible.

FIG. 3. — Anterior surface of the lumbar vertebra of Hare (Ltfus tintiJtis). s spinou
process ; m meupophysis ; as anterior zygapophysis ; t transverse process ;
hypapophysis.

The principal processes commonly met with are as
follows : —

1. From the middle of the upper part of the arch, a process
(Fig. 3, s) generally single, but sometimes bifid at the end,
grows out vertically. This is the spinous process, or neural
spine already mentioned ; about its homology in different
vertebrae there never can be any question. It may, however,
be completely absent when the arch is round or smooth
above, as in the cervical region in some animals ; on the
other hand, it may grow out into a very long conspicuous
rod of bone, as in the anterior dorsal region of others.

2. Occasionally a process grows in the median line from
the under-surface of the body. This may be single and long
and slender, as in the anterior lumbar vertebrae of the Hare

20 THE VERTEBRAL COLUMN. [CHAP-

(Fig. 3 , h\ or a sharp median ridge, as in the cervical verte-
brae of many Ungulata and the cervical and caudal vertebrae
of the Ornithorhynchus, or double, as in the atlas vertebra of
the last-named animal and the caudal vertebros of many others.
This is termed a hypapophysis. Most commonly there is not
even a trace of any such process.

3. From the sides of the lower part of the arch, or from
the body, lateral processes project more or less directly out-
wards. These are called transverse processes. There may be
but one, or there may be two, superior and inferior, on each
side of a vertebra. In the latter case the superior is some-
times called a diapophysis^ and the inferior a parapophysis :
though it is questionable whether the processes to which
these terms have been applied can always be regarded as
strictly homologous.

4. Besides these principal laterally projecting processes,
there are often others arising from the side of the arch, more
especially developed in the lumbar region, though by no
means constant even there. Of these there may be one or
two on each side. They have often been called accessory

in.] DEVELOPMENT. 21

processes ; but in the more precise system of nomenclature
introduced by Sir Richard Owen, the one which is situated
highest on the arch (see Fig. 4, m), projects more or less
forwards as well as outwards, is usually thick and rounded,
and is nearly always in relation with the anterior zygapo-
physis, is termed metapophysis ; l the one placed rather lower
(Fig. 4, a), and which projects more or less backwards, and
is generally rather slender or styliform, is called anapophysis.
These, with the zygapophyses before mentioned, sometimes
called oblique processes, but which are rather articular surfaces
than true processes, are all the processes commonly met with
on any Mammalian vertebra.

Development of the Vertebra. — The first indication of the
formation of a vertebral column in the embryo is the
appearance of a longitudinal primitive dorsal groove in the
germinal membrane, the edges of which (lamina dorsales)
rise up and meet above, so as to convert the groove into a
canal. From the tissue lining this canal (uppermost layer
of the germinal membrane) the brain and spinal cord are
developed, and in its walls are formed anteriorly the cranium,
and posteriorly the vertebral column ; the canal itself
becoming the cerebral cavity and the neural canal of the
spine.

In the floor of this canal, formed by a horizontal lamina
which separates it from another and larger, ventral or haemal
canal (formed by the approximation in the middle line below
of the lamina rentrales), a slender rod of peculiar structure
is developed. This is the notodwrd or chorda dorsalis,
around which the bodies of the future vertebrae are deve-
loped. In the Mammalia it almost completely disappears at

1 It is also called " mammillary process " in some works on Human
Anatomy.

22 THE VERTEBRAL COLUMN. [CHAP.

a very early period, traces only remaining in the axis of the
intervertebral substance, though in many of the inferior
Vertebrata it is persistent as a continuous rod for a longer
period, and sometimes permanently.

The formation of the arches of the vertebrae in the
lamina dorsalcs is preceded by the appearance of dark-
looking cellular masses called proto-vertebrce or somatomes,
corresponding in number, though not exactly in situation, to
the future vertebrae, and which undergo a series of changes
(for a description of which the student is referred to special
treatises on embryology) out of which ultimately results a
vertebra, similar in shape to that which it presents in adult
life, but formed of a continuous piece of hyaline cartilage.

The mode of ossification of this cartilaginous vertebra in
the different groups of Mammals still offers an interesting
field for investigation, but the following is a summary of the
most important facts ascertained regarding it.

Leaving out for the present the greatly modified two
anterior vertebrae, the atlas and the axis, which must be
specially considered afterwards, and also the comparatively
rudimentary vertebrae of the caudal region, each vertebra
consists at one period of three pieces of bone, as distinct
from each other, and remaining so for as long a period, as
many of the separate elements of the skull.

One constitutes the greater part, but usually not the whole,
of the body or centrum. Each of the others forms one side
of the arch, and usually more or less of the upper lateral
part of the body. These last ultimately unite to each other
in the middle line above, and to the central piece on each
side below. The line of union between them and the central
piece is readily distinguishable in all vertebrae up to the time
the animal is about half-grown, and is named by Professor
Huxley the neuro-central suture. (See Fig. 8, p. 33, ncs.)

in.] DEVELOPMENT. 23

As a general rule all the processes (except the hypapo-
physes) arise from the part of the vertebra situated above
the neuro-central suture, but there are notable exceptions.

The body of the vertebra is nearly always completed by
the addition of a thin disk-like epiphysis at each end, which
for a considerable period after it is fully ossified remains
adhering by a rough surface to the central or main part
of the body, and is easily separated from it by maceration.
Its coalescence with the remainder of the body, especially in
the thoracic region, is one of the last acts in the completion
of the bony skeleton, and does not take place until after all
the epiphyses of the limb bones are firmly united. Hence
it may be taken as a safe indication that the animal is
thoroughly adult.

It must be noted that the epiphysis covers the whole
surface of the end of the body, whether ossified from the
centrum or the arch, and is therefore quite independent of
the position of the neuro-central suture.

These terminal epiphyses to the bodies of the vertebrae
are peculiar to the Mammalia, but not found universally
throughout the class, as they are wanting, or, at all events,
very imperfectly developed, in the Monotremata and the
Sirenia. In man, the highest apes, and also in some of the
Marsupialia, they have less solidity and importance than in
other Mammals, being often mere thin osseous rings, repre-
senting the circumferential portion only of the ordinary
epiphysis.

The various processes of the vertebrae have been divided
into those that are autogenous, or formed from separate
ossific centres, and exogenous, or outgrowths from either of
the just-mentioned primary vertebral constituents.

There can be no doubt but that an autogenous process
of one vertebra of an animal may be serially represented

24 THE VERTEBRAL COLUMN. [CHAP.

by an exogenous process in another vertebra of the same
animal ; l and likewise that the corresponding processes of
the same vertebra may be developed exogenously in one
animal and autogenously in another.

In nearly all the more prominent processes, moreover,
whether formed by exogenous or autogenous ossification,
the extreme tip remains cartilaginous for a considerable
time ; and at a comparatively late period in developmental
life (near the approach of maturity) a small ossific centre
forms in it. This spreads through the cartilage, and then
constitutes an epiphysis, which ultimately unites to, and
becomes indistinguishably incorporated with, the remainder
of the process.2

The spinous process is either formed by the coalescence
of outgrowths from the two pieces forming the neural arch,
or the greater part of it may be (as in the long spines of the
anterior thoracic vertebrae of Ungulates) formed by a very
early autogenous ossification, which soon becomes united to
the upper part of the arch. In either case it is usually com-
pleted by an epiphysis of comparatively late ossification.

There is one part connected with certain vertebrae which
requires some particular consideration, on account of the
great modifications it presents, being in some regions a
largely developed independent bone, articulated with the

1 Even the arches of some of the caudal vertebra; appear to be
ossified directly from the body, and not independently, as is the rule
in the thoracic and lumbar vertebras.

2 These epiphyses are sources of considerable difficulty in tracing
homologous parts, as it is questionable whether they should be treated
as separate elements of the skeleton, and, if not, where to draw the
line between an epiphysis and an element. They often appear mere
conveniences of growth, as it were, being developed upon the end of
a process when it is long, and being absent in a corresponding part of
stunted dimensions.

in.] DEVELOPMENT. 25

vertebra by synovial joints, and in other regions a small
rudiment, early and firmly united to, and incorporated with,
the vertebra itself.

The ribs in the thoracic region, though primarily formed
from a rod of cartilage continuous with that of the vertebra,
always become distinct, independent, and movably arti-
culated bones; after their original segmentation they can
never be properly said to constitute part of the vertebra.
But it frequently happens that in certain of the vertebras
anterior to the thoracic region, and in certain of those
posterior to it, there are bony elements formed at an early
period, which, though very different from ribs in the ordinary

FIG. £. — Third cervical vertebra of a nearly full-grown Echidna (E. aculeata), the
different pieces of which it is composed being slightly separated from one another.
ma neural arch ; c centrum ; / transverse process ; v vertebrarterial canal ; IKS
neuro-central suture.

sense of the word, occupy a somewhat similar position
in relation to the vertebrae to that which the ribs do in the
thoracic region. These have hence been considered as
modified conditions of the same part, and have been called
pleurapophyses by Professor Owen.

Perhaps the clearest case of the presence of rib elements
in the vertebrae in any Mammal is afforded by the cervical
vertebrae of the Monotremata, where the greater part of each
transverse process ossifies separately from the rest of the ver-
tebra, and remains for a long time only suturally connected
with it (Fig. 5). They thus closely correspond to the cervical

26 THE VERTEBRAL COLUMN. [CHAP.

ribs of reptiles, which are unquestionably homologous serially
with the thoracic ribs.

The anterior, or more properly inferior, bar of the trans-
verse process of the seventh, and occasionally of some of the
other cervical vertebrae in Man, is autogenously developed,
and has some characters by which it may be placed in the
category of rudimentary ribs.

The transverse processes of the anterior lumbar vertebra?
of certain Mammals, as the Pig, are originally autogenous
elements, though coalescing very early with the rest of the
vertebras.

In the sacral region, the separate lateral ossifications which
connect the vertebral column with the ilium present many
characters allying them to ribs. (See Fig. 6.)

FIG. 6. — Anterior surface of first sacral vertebra (human) showing mode of develop-
ment, na neural arch ; t centrum ; p distinct (pleurapophysial) ossification fur
attachment of ilium.

Finally, the transverse processes of the caudal vertebra? of
some animals (as the Manatee and Beaver) are separately
developed, though it is doubtful whether this circumstance
alone is sufficient to entitle them to be considered as costal
elements.

Division of the Vertebral Column into Regions. — For con-
venience of description the whole vertebral column has

in.] DIVISION INTO REGIONS. 27

been divided into five regions, the cervical, thoracic? lumbar,
sacral, and caudal.

This divison is useful, especially as it is not entirely
arbitrary, and in most cases is capable of ready definition,
at least in the Mammalia ; but at the contiguous extre-
mities of the regions, the characters of the vertebra of one
are apt to blend into those of another region, either nor-
mally, or as peculiarities of individual skeletons.

i. The Cervical region constitutes the most anterior por-
tion of the column, or that which joins the cranium.

The vertebrae which belong to it are either entirely
destitute of movable ribs, or, if they have any, these art-
small, and do not join the sternum.

az

FlG. 7.— Anterior surface of sixth cervical vertebra of Dog, \. t spinous process ;
as anterior zygapophysis ; v vertcbrarterial canal; / transverse process; f it*
inferior lamella.

As a general rule they have a considerable perforation
through the base of the transverse process (the rertc
brarterial canal Owen), or, as it is sometimes described,

1 Generally called dorsal, but it would be better to reserve this term
in morphology as relating to the upper surface of the body and opposed
to ventral.

28 THE VERTEBRAL COLUMN. [CHAI>.

they have two transverse processes, superior and inferior,
which, meeting at their extremities, enclose a canal. (See
Fig. 7 ; Fig. 8, p. 33 ; and Fig?. 17 and 18, p. 45, 46.) This,
however, rarely applies to the last vertebra of the re-
gion, in which only the upper transverse process is usually
developed.

The transverse process moreover very often sends down
near its extremity a more or less compressed plate (inferior
lamella, Fig. 7, /"), which being considered to be serially homo-
logus with the ribs of the thoracic vertebrae (though not
developed autogenously) is often called " costal " or " pleura-
pophysial " plate. This is usually largest on the sixth, and
altogether wanting on the seventh vertebra.

The first and second cervical vertebrae, called respectively
atlas and axis, are specially modified for the function of
supporting, and permitting the free movements of the head.
They are not united together by an " intervertebral sub-
stance," but connected only by ordinary ligaments and
synovial joints.

The cervical region in Mammals presents the remarkable
peculiarity that, whatever the length or flexibility of the
neck, the number of vertebroe is the same, viz. seven, with
very few exceptions, which will be particularised further on.

2. The Thoracic or Dorsal region consists of the vertebrae
which succeed those of the neck, having ribs movably
articulated to them. These ribs arch round the thorax, the
anterior one, and most usually some of the others, being
attached below to the sternum.

The characters of the ribs and their mode of articulation
with the vertebras will be considered further on, but it may
now be stated that in the anterior part of the thorax the
vertebral extremity of each rib is divided into " head " and
" tubercle " ; that the former is attached to the side of the

in.] DIVISION INTO REGIONS. 29

body of the vertebra, the latter to its transverse process :
and that the former (capitular) attachment corresponds to
the interspace between the vertebras, the head of the rib
commonly articulating partly with the hinder edge of the
body of the vertebra antecedent to that which bears its
tubercle. Hence the body of the last cervical vertebra
usually supports part of the head of the first rib. In the
posterior part of the series the capitular and tubercular
attachments commonly coalesce, and the rib is attached
solely to its corresponding vertebra.

3. The Lumbar region consists of those vertebra of the
trunk in front of the sacrum (to be afterwards defined) which
bear no movable ribs. It may happen that as the ribs
decrease in size posteriorly, the last being sometimes more
or less rudimentary, the step from the thoracic to the
lumbar region may be gradual and rather undetermined in
a given species. But most commonly this is not the case,
and the distinction is as well defined here as in any other
region.

As a general rule there is a certain relation between the
number of the thoracic and the lumbar vertebrae, the whole
number being tolerably constant in a given group of
animals, and any increase of the one being at the expense of
the other. Thus in almost ail Artiodactyle Ungulata there
are 19 thoracico-lumbar vertebras; but these may consist of
12 thoracic and 7 lumbar, or 13 thoracic and 6 lumbar, or
14 thoracic and 5 lumbar.

The smallest number of thoracico-lumbar vertebrae in
Mammals occurs in some Armadillos, which have but 14.
The number found in Man, the higher Apes, and most Bats,
viz. 17, is exceptionally low ; 19 prevails in the Artiodactyles,
nearly all Marsupials, and very many Rodents; 20 or 21 in

30 THE VERTEBRAL COLUMN. [CHAP.

Carnivora and most Insectivora, 23 in Perissodactyla. The
highest and quite exceptional numbers are in the two-toed
sloth (Chold'pus) 27, and Hyrax 30.

The prevailing number of rib-bearing vertebrae is 12
or 13, any variation being generally in excess of these
numbers.

4. The Sacral region offers more difficulties of definition,
especially at its posterior portion.

Taking the human " os sacrum " as a guide for comparison,
it is generally defined as consisting of those vertebra?, between
the lumbar and caudal regions, which are ankylosed together
in the adult state to form a single bone. It happens, how-
ever, that the number of such vertebrae varies in different
individuals of the same or nearly allied species, especially as
age advances, when a certain number of the tail vertebrae
generally become incorporated with the true sacrum.

A more certain criterion is derived from the fact that some
of the anterior vertebrae of the sacral region have distinct
additional (pleurapophysial) centres of ossification, between
the body and the ilium (see Fig. 6, p. 26). To these perhaps
the term sacral ought properly to be restricted, the remaining
ankylosed vertebrae being called pseudo-sacral, as suggested
by Gegenbaur. Our knowledge of the development of the
sacrum in different animals is not sufficient at present to
apply this test universally, but it appears probable that two
is the most usual number of true sacral vertebrae, as thus
defined in the Mammalia.

5. The Caudal Vcrtebrcc are those placed behind the
sacrum, and terminating the vertebral column. They van-
in number greatly, being reduced to 5, 4, or even 3, in a
most rudimentary condition, in Man, some Apes and Bats,
and being numerous and powerfully developed with strong

1 1 i.l DIVISION INTO REGIONS. 31

and complex processes in many Mammals, especially among
the Edentata, Cetacea, and Marsupialia. The highes
known number, 49, is possessed by the African Long-tailed
Manis. (Af ant's mafrura.) A small Insectivora, Microgale
longicaudata from Madagascar has sometimes as many as
47, but in these cases there is considerable individual
variation.

CHAPTER IV.

SPECIAL CHARACTERS OF THE CERVICAL VERTEBR/E IN THE
MAMMALIA.

ORDER PRIMATES. — The human cervical vertebrae (ex-
cluding for the present the first and second) have short,
wide, depressed bodies, hollowed in front from side to side,
and behind from above downwards,1 with wide neural canals,
and short, broad, and usually bifid spines (considerably
longer in the seventh vertebra than in the others), well
marked, broad, flat, anterior and posterior zygapophyses,
and short, sub-bifid, widely perforated transverse processes.

These vertebrae are, as usual, developed mainly from three
centres, one for each side of the arch, and one for the
centrum (see Fig. 8), but it will be observed that the whole
of the body is not formed from the latter, but that its lateral
parts, with the transverse processes, are ossified from t In-
arches.

Besides these main centres of ossification there are thin
and imperfect disk-like epiphyses on the ends of the body,

1 As before mentioned, the body is supposed to be placed horizontally,
^o that the same terms of relative position may be used as when speak-
ing of the vertebral column of the ordinary less modified animals of the
class.

CHAP, iv.] CERVICAL VERTEBRA. 33

very late in making their appearance, and not joined until
long after the rest of the vertebra is completed. A small
epiphysis is also formed on the end of the spinous
process.

Lastly, the inferior or ventral bar of the transverse process
of the seventh vertebra is developed from a separate centre
of ossification, and occasionally the same part of the sixth
and fifth has its own separate nucleus. This bar of bone is
connected internally with a projection from the side of the
body, ossified from the arch ; externally with the end of the
upper or true transverse process, which is an exogenous

FIG. 8. — Sixth cervical vertebra of a child, i. c centrum ; net neuro-central suture ;
T' vcrtcbrarterial canal ; az anterior zygapophysis.

growth from the arch, so that it is attached to the vertebra
entirely above the neuro-central suture. Occasionally it
acquires an abnormal development, and grows into a con-
siderable rib-like bone, in which case it is usually united at
its distal extremity with the first thoracic rib.

The first vertebra or atlas (Fig. 9) is little more than an
oval ring, thickened on each side into the so-called " lateral
mass," which bears an articular surface before and behind.
The anterior surfaces are very large, elongated from above
downwards, and hollowed for the reception of the condyles of
the occiput. The posterior articular surfaces are subcircular

CERVICAL VERTEBRAL.

[CHAP.

flattened, or slightly-concave. The transverse processes are
short, stout, and perforated ; the arch presents scarcely a
rudiment of a spinous process. On its anterior edge im-
mediately above the articular surface is a deep notch or
groove (g) of some importance, as it corresponds with the
slight notch in front of the pedicle in other vertebras, which
contributes with the deeper notch in the hinder border of
the pedicle of the preceding vertebra to form the " inter-
vertebral " foramen for the exit of a spinal nerve, and because,
occasionally in man, and constantly in many animals, it is
converted by a bridge of bone into a canal, through which

FIG. 9. — Human atlas, young, showing development. :]. in inferior arch ; as articula

surface for occiput ; t transverse process ; g- groove for first spinal nerve am

the first cervical (or subocdpitat) nerve passes out. The
inferior arch of the atlas (ia) differs entirely from the bodies
of the other vertebrae, being a simple, depressed, slightly
curved bar of bone, with a smooth facet on its neural or
upper surface, for articulation with the odontoid process of
the axis.

The second cervical vertebra, axis, epistropheus, or vertebra
dentata (Fig. 10), has a body terminating anteriorly in a
large subconical median projection, the odontoid process
(o), which is received into, and articulates with, the con-
cavity of the inferior arch of the atlas. It is retained in

IV.]

MAN.

35

its place by means of a strong transverse ligament passing
between the lateral masses of that bone, and separating its
canal into an upper or neural portion for the passage of the
spinal cord, and an inferior portion for the reception of the
odontoid process.

The axis has posterior zygapophyses placed on the arch,
serially continuous with those of the rest of the vertebrae, but
its anterior articular facets, like those of the atlas, do not
belong to the arch proper, but partly to the body and partly
to the arch, and are therefore not exactly serially homologous

FIG. 10.— Diagram showing mode of ossification of human axis (ha:mal or vential
surface), o odontoid process, or centrum of atlas ; c proper centrum of axis ; na
neural arch ; as anterior articular surface ; e t e epiphyses, completing the ends of
the centra.

with the zygapophyses of the other vertebrae. The trans-
verse processes are short, single, and perforated. The arch
is high, with a stout bifid spine.

The development of the atlas and axis offers some im-
portant points for consideration.

The arch of each is ossified from two centres, one on each
side, as in other vertebrae ; but if the axis is examined a year
or two after birth (Fig. 10), its body appears to be composed
of two parts, one placed in front of the other, the first includ-
ing the odontoid process and the anterior part of the body,

1) 2

36 CERVICAL VERTEBRA-.. [CHAP.

the second all the remainder of the body. The arch is
united to both. On the other hand, the atlas at the time
of birth has nothing corresponding to the centrum of other
vertebras, its inferior arch being still cartilaginous.

It is therefore a generally received opinion among ana-
tomists that the anterior ossification of the axis is essentially
the body of the atlas, which unites with both arch and
centrum of the vertebra behind it. It must be observed,
however, that in its mode of ossification, at least in Man, it
differs from the contra of all the other vertebras, as at one
period it consists of two distinct lateral pieces, which after
a while coalesce in the middle line. The usual disk-like
epiphyses of the vertebral bodies are represented by one
at the posterior extremity of the body, by a small osseous
nodule which completes the odontoid process in front, and
by some irregular ossifications found between the two main
portions of which the body is composed.

The inferior arch of the atlas ossifies soon after birth
from one or more centres, and the resulting piece of bone
(Fig. 9, id] ultimately unites with the two pieces forming
the neural arch about the same time as that at which they
join together in the middle line above. This piece may
probably be regarded as a detached " hypapophysial " seg-
ment of the first vertebral centrum, the remainder of which
forms the odontoid portion of the body of the axis.

The cervical vertebras of the other PRIMATES resemble
those of Man generally, the most noticeable deviations being
the following : —

In the atlas the groove for the first cervical nerve is usually
converted into a foramen ; and a median hypapophysial
tubercle or spine often projects backwards from its inferior
arch under the axis (especially in Mycetes and Lagothrix).

The spinous processes, especially of the third, fourth,

iv.] CARN1VORA. 37

fifth, and sixth cervical vertebrae, are immensely elongated
in the Gorilla, and considerably so in the Chimpanzee and
Orang. These processes as a rule are not bifid, as in Man,
but occasionally (as in Mycetes) they are trifid, having a pair
of lateral backward-projecting processes developed near
their extremity.1

The inferior lamellae of the transverse processes are
generally larger proportionally than in Man, especially in the
Lemurina. In the seventh vertebra, the transverse processes
vary much as to their perforate or imperforate condition.

In the CARNIVORA, the atlas (Fig. n) has very deep
anterior articular surfaces for the condyles of the skull. The

FlG. ii. — Inferior surface of atlas of I>og, J. in foramen for first spinal nerve ;

'• vc-rtctjr.irtcn.il canal.

first spinal nerve passes through a complete foramen. The
transverse processes are large, wing-like, flattened from above
downwards, and perforated by the vertebrarterial canal.

The axis (Fig. 12) has a long conical odontoid process,
and a large compressed neural spine, greatly extended from
before backwards, and especially produced forwards.

The remaining cervical vertebras have small, narrow,
compressed, usually simple spines, gradually lengthening to
the seventh, and large transverse processes, with greatly

1 These are named hyperapophysu by Mivart, who has called par-
ticular attention to them : "On the Axial Skeleton in the Primates : "
Proc. Zool. Soc. 1865, p. 545.

33 CERVICAL VERTEBRAL. [CHAP.

developed inferior lamellae (see Fig. 7, p. 27, /') especially
large in the fifth and sixth. In the latter the lower edge of
this lamella is frequently hollowed in the middle, and pro-
duced at each extremity, so that the transverse process has
a trifid appearance. This is especially marked in the Felida.
The transverse process of the seventh vertebra has no inferior
lamella, and its base is imperforate.

Metapophyses are generally more or less developed on the
cervical vertebrae of the Carnivora, and there are also in
some genera small backward projecting tubercles (Jiyperapo-
physesy Mivart) situated on the laminae of the arch, rather

FIG. 12. — Side view of axis of Dog, jj. s spinous process; o odontoid process ;
pz posterior zygapophysis ; / transverse process ; v vertebrarterial canal.

internal to the posterior zygapophyses, not usually found in
other vertebra;.

In the INSECTIVORA the cervical vertebras vary consider-
ably in their characters. The atlas has usually short trans-
verse processes. Generally the spinous process of the axis is
large and prominent, and that of the other vertebrae very
small, but in Centetes and Pofanwgale they are all more or less
elongated. The neural arches in some (as Myogale and
Sorex) are reduced to mere filaments. In the mole (Talpa}
the transverse processes of the fourth, fifth, and sixth
vertebra; are much expanded antero-posteriorly, and overlap

iv.] RODENTIA. 39

each other. Large single hypapophyses are developed from
the inferior surface of most of the cervical vertebras in the
Shrews (Sorex) and some of their allies, and in Galeopithecus
each vertebra bears at its hinder end a pair of hypapophysial
tubercles.

In the CHIROPTERA all the cervical vertebrae are broad,
very short from before backwards, with slender neural arches
from which (except in the axis) no distinct spinous processes
are developed. In certain forms (as Vesptrugo) some of the
vertebras have distinct double hypapophysial spines project-
ing backwards.

In the RODENTIA the atlas has usually broad, moderately
long, wing-like transverse processes. The odontoid process
is long and slender ; the spinous process of the axis is much
developed, while as a rule that of the other cervical vertebras
is exceedingly small. The transverse processes of the fifth
and sixth have large inferior lamellas ; that of the seventh
is sometimes perforated at the base (as in Ltptts), and
sometimes imperforate (as in Hydrochcerus).

In the Capybara (Hydrochcerus) and some others, the side
of the arch of the atlas is perforated near its anterior border
for the exit of the first spinal (sub-occipital) nerve, and also
near its hinder border for the second cervical nerve.

In the Jerboas (Difus) a very exceptional condition of
the cervical vertebras occurs. The atlas is free, but all the
others are ankylosed together by both bodies and arches,
and the bodies are very wide and depressed, as in the
Armadillos.

Among the UXGULATA, the atlas (Fig. 13) in the Pecora is
very long, with deep articular cavities for the occipital con-
dyles. The transverse processes are not wide, but much
extended from before backwards, and flattened from above
downwards. Each is perforated by a foramen (sn) which gives

CERVICAL VERTEBR.-E.

[CHAP.

exit to the inferior division of the first cervical nerve, but not
by the vertebral artery, which usually enters the neural canal
between the arches of the second and third vertebra;. The
odontoid process of the axis (Fig. 14) is of peculiar shape,

being like a spout, or hollow half-cylinder, with a prominent
sharp semicircular rim. The canal for the second cervical

spinal nerve pierces the lamina of the axis near its anterior
border. The other vertebra? have more or less elongated
bodies, which are opisthocalous, i.e. concave behind and
convex in front. They are keeled below, the keel being often

iv.] UNGULATA. 41

developed into a hypapophysial spine posteriorly ; the neural
spines are moderately long, and inclined forwards. The
transverse processes of the fifth, and especially of the sixth
have large inferior lamella;. That of the seventh is usually
im perforate.

In the Giraffe the bodies of the cervical vertebra; are very
long. The transverse processes are short, but so extended
from before backwards as to become divided into two, one
at the anterior and one at the posterior end of the vertebra.
That of the seventh is perforated.

In the Tylopoda (Camels and Llamas) the vertebrarterial
canal passes obliquely through the anterior part of the
pedicle of the arch, being in its posterior half confluent with
the neural canal. A similar condition occurs in Afacrau-
chenix, an extinct South American Perissodactyle Ungulate.

The Suina and Tragulina differ from the remaining exist-
ing Artiodactyles in the form of the odontoid process, which
is conical ; while on the other hand the Horse and Tapir
among the Perissodactyles have this process wide, flat, and
hollowed above, approaching the form it presents in the
Ruminants. In the Pig, the broad pedicles of all the cervical
vertebra; are perforated by canals for the passage of the
upper division of the spinal nerves.

The bodies of the cervical vertebra; in the Rhinoceros,
Tapir, and Horse are markedly opisthocoelous. but in the
Pig and Hippopotamus very slightly so.

In the Horse the bodies of the cervical vertebra; are
elongated, with a strong keel and hypapophysial spines.
The neural lamina; are very broad, the spines almost obso-
lete, except in the seventh, and the transverse processes not
largely developed. The seventh is not perforated by the
vertebrarterial canal.

In the Rhinoceros, on the other hand, the bodies are

42 CERVICAL VERTEBRA. [CHAP.

comparatively short, and not keeled, the laminae narrow, the
spines well marked, and the transverse processes greatly
developed, especially those of the atlas.

In the Elephant (order PROBOSCIDEA), the atlas much
resembles the human atlas. The axis has a short conical odon-
toid process and a very massive spine, broad above and bifid
posteriorly. The bodies of the other vertebrae are very short,
flattened, sub-circular disks, very slightly opisthoccelous.
Excepting the seventh they all have short spinous processes,
and short, broad, and largely perforated transverse processes.
The seventh has a high spine, an imperforate transverse pro-
cess, and on the hinder edge of its body a very distinct arti-
cular cavity for the head of the first rib. In the young animal
this is divided into two equal parts by the neuro-central
suture.

In the order SIRENIA, the Dugong (Halicore) has seven
cervical vertebrae, as in the Mammalia generally. The atlas
has short imperforate conical transverse processes. The axis
has a high arch and massive neural spine, a short rounded
odontoid process, and very rudimentary transverse processes.
The others have short and wide bodies, small spines, and
irregularly developed transverse processes, often not com-
pletely enclosing a vertebrarterial canal.

The Rhytitta, a large animal of this order, which became
extinct towards the close of last century, had also seven
cervical vertebrae, and the Miocene Halitherium had the
same number.

The Manatees (genus Manatus), of which there are two
well-marked forms, one inhabiting the west coast of
Africa, and the other the east coast of Central and South
America, never have more than six vertebras in the cervical
region. These resemble generally those of the Dugong,
having short and wide bodies, and very irregular transverse

iv.] CETACEA. 43

processes. In a specimen of Manatus senegalensis^ in the
Museum of the College of Surgeons, the second and third
are ankylosed by their bodies, and the neural arches of most
of the others are widely open above. In the skeletons of M.
americanuS) in the same museum, the vertebrae are all free,
and the arches, though slender, are complete, and with very
slightly developed spinous processes. In a specimen of J/.
americanus in the Museum of Cambridge the axis and atlas
have large neural spines ; the vertebrarterial canal is incom-
plete in the 2nd, 3rd and 4th vertebra, wanting in the 5th,
but complete in the 6th which carries a distinct movable
cervical rib.

In the Cetacea the seven cervical vertebrae usually found
in the Mammalia are always present, though often so short
and blended together, that it is not easy at first sight to re-
cognise their existence. In some genera of both sub-orders
all the vertebne are free, though never allowing of much
motion between them ; but more commonly certain of them
are firmly united together by bone. Even where the atlas
and axis are separate the odontoid rarely forms a distinct
process (it is most distinct in Platanista), but still it is devel-
oped from an ossific centre of its own, as in other Mammals.

Among the Mystacoceti, in the Right Whales (genus
Balana) the whole of the seven cervical vertebra? are usually
united into one mass by their bodies, though sometimes the
seventh is free. The arches are also more or less united
above, though generally not in a continuous mass. Small
slit-like openings between the narrow pedicles of the arches
permit the exit of the cervical spinal nerves, and in the adult
condition afford the only indications by which the number of
the united vertebrae can be ascertained. Already before
birth most of the bodies have coalesced, and it is even
doubtful whether they ever exist in a separate condition.

•14

CERVICAL VERTEBRA.

[CHAP.

The Fin Whales or Rorquals (genus Bal&noptcra) present
a totally different condition of cervical vertebra?, as these are,
as a rule, all distinct and free, though occasionally, as an
individual peculiarity, an irregular ankylosis may take place
between two or more of them.1

FIG. 15. — Section through middle line of united cervical vertebra; of Greenland Right
Whale (Balcena inysticctus), J. particular surface for occipital condyle ; e epi
physis on posterior end of body of seventh cervical vertebra : sn foramen in arch
of atlas for first spinal nerve ; i arch of atlas ; 2 3 4 5 6 conjoined arches of the
a.\is and four following vertebra; ; 7 arch of seventh vertebra.

In the common large Fin Whale of our coasts (//.
musculns) the atlas (Fig. 16) has short, stout, conical, imper-
forate transverse processes. The axis (Fig. 17) has a broad
oval body, high massive arch, very short odontoid process,
and very wide, oblong wing-like transverse processes directed
somewhat backwards, and with an oval perforation near the

1 Sec Professor Struthers '
Articulations in Fin Whales."
November 1872.)

On the Cervical Vertebra: and their
(Journal of Anatomy and Physiology,

CETACEA.

45

base. The other cervical vertebrae (Fig. 18) have similar
broad, very short bodies, small arches, without spines, and
very long transverse processes, composed of slender upper

Fie. 16 — Anterior surface of at las of common Fin Whale (!>al<rnt>ftfra ntuscntits). ,'..
in foramen for first spinal nerve.

and lower bars, widely separated at their bases, but united at
their extremities so as to enclose a very large space between
them. In the seventh the upper process only exists, and the

Flc. 17. — Anterior surface of axis of common Fin Whale (Balitncptera. tnufctilus), i .
a odontoid process.

lower one is occasionally imperfect in the sixth.1 In very
young animals these processes are formed only of cartilage •

1 Professor Turner has shown that, in a foetal BaLmoftera si
the inferior transverse process of the seventh is present in a cartilagi-
nous condition. (Journal of Anatomy and Physiology, May 1871.)

46

CER VIC A L VER TEBR.-E.

[CHAP.

and as ossification takes place gradually from within out-
wards, and does not reach the outer extremity until the
animal approaches maturity, specimens are frequently met
with in museums, which, instead of completely annular
transverse processes, show only truncated upper and lower
bars. In some species, however (as in Megaptera boops),
most of the cervical vertebras remain permanently in this
condition.

FIG. 18. — Anterior surface of fourth cervical vertebra of the same animal, J«. as ante-
rior of zygapophysis ; t upper transverse process ; t' lower transverse process.

Among the Odontoceti, all the cervical vertebree are free in
the Gangetic Dolphin (Platanistd), and in the allied South
American genera Inia and Pontoporia, also in the Nar-
whal (Monodon) and the Beluga, or the White Whale. In
most of these genera the atlas has a large hypapophysial
process, projecting under and articulating with the body of
the axis, which develops no distinct odontoid. In the
Narwhal irregular ankyloses between the bodies of the cervical
vertebrae are very frequent. In all the other Delphinidcc
(including Delphinus, Orca, Psendorca, Glolncef>Jialns, Pho-
ama, &c.), at least the first and second cervical vertebras
are united by both body and spine, and most commonly
some of the succeeding vertebrae are joined to them. If
any are free, it is always those situated most posteriorly,
and they have extremely thin, sub-circular disk-like bodies,

iv.] EDENTATA. 47

and irregular and comparatively rudimentary transverse
processes.

In Hyptrcodoti) the whole of the cervical vertebrae are
ankylosed together. In the other Ziphioids several of the
posterior vertebne are free, and the allied Cachalot, or Sperm
Whale (Physeter), presents a condition not met with in any
other known Cetacean : the atlas is free, and all the other
neck vertebrae are completely united.

Among the various members of the order EDENTATA, the
cervical vertebne present very different conditions.

In the Armadillos (Dasypodidcc) the bodies are extremely
short, broad, and depressed, and several are commonly anky-
losed together ; the corresponding neural arches being also
united, the neural, and to a certain extent the vertebrarterial,
canals form continuous tubes. The orifices for the spinal
nerves perforate the united pedicles. The atlas is always
free. The vertebrae that are united are the second and third,
or the second, third, and fourth ( Tatusia pcba), and in some
species the fifth also. The spinous processes of the axis and
those of the fused vertebrae in general are very large, but the
neural arches of the hinder free vertebrae are extremely
narrow, and the spinous processes rudimentary. The trans-
verse process of the seventh has an inferior lamella, nearly
as large as that of the sixth, and is not perforated.

In Orycteropits, the Pangolins (Mam's), and the Anteaters
(Myrmccophagd)) the neck vertebra? are more normal in form,
and are not ankylosed. In the last-named genus, the verte-
brarterial canal of several (2, 3, 4, in M. jubata) of the
vertebras perforates the pedicle obliquely, and enters the
neural canal posteriorly, much as in the Camels.

Among the leaf-eating Edentates, or Sloths, the neck
vertebrae present some remarkable peculiarities, especially as
to number.

48 CERVICAL VERTEBR.E. [CHAP.

All the known species of three-toed Sloths (genus Brady-
pus] have nine cervical vertebra, i.e. nine vertebrae in front
of the one which bears the first thoracic rib (or first rib con-
nected with the sternum, and corresponding in its general
relations with the first rib of other Mammals), but the ninth,
and sometimes the eighth, bears a pair of short movable
ribs. The eighth is perforated by the vertebrarterial canal,
but not the ninth.

The common species of two-toed Sloth (C/wlcepus didac-
lylus] has seven cervical vertebra?, but a closely allied
species (C. Iwffmannii) has but six. In both cases the
vertebrarterial canal is continued to the end of the series,
the sixth and seventh cervical vertebra: respectively.

In the very heterogeneous order MARSUPIALIA (sub-class
Didelphia) the cervical vertebrae vary much in their characters,
though the number is always seven, as in the great majority
of the Mammalia.

One of the most important variations is in the mode of
ossification of the atlas. In the Wombat (Pliascolomys}.
Koala (Phascolarctos), P/ialangisfa, and Kangaroo (Macro-
pus), there is no distinct osoific nucleus in the inferior arch
of the bone, which remains either permanently open in the
middle line below, or (as in some of the smaller Kangaroos)
is completed by the union of prolongations of the arches
inwards. This, however, is not the case with the carnivorous
Marsupials. In the Thylacine (see Fig. 19) there is a distinct
heart-shaped piece of bone in the centre of the inferior arch
of the atlas, which appears never to become united to the
remainder, as it is still attached by ligament in skeletons
otherwise perfectly mature, and is commonly lost in mace-
ration. In Perameles and Didelphys the atlas is completely
ossified below by a wide intermediate piece, quite as in
ordinary Mammals.

iv.] MARSUPIALIA. 49

As to the other vertebne, in the Kangaroos the transverse
processes are long and slender, and (including the seventh)
have a very small perforation close to the base. The inferior
lamella arises near the base of the process, and is very
large in the sixth, but generally absent in the seventh
vertebra.

In the Wombat, the bodies are wide and depressed. The
transverse processes are perforated in all ; the inferior
lamella of the sixth is much developed antero-posteriorly.
The spines of all are rather short.

Fir,. 19. — Inferior surface of atlas of Thylacine (Tkyl&cinMt ejmotefilialiii). \. A dis-
tinct ossification in centre of inferior arch, with pointed hypapophysial pro-
jection.

In Pframeles lagotis the greater jxirt of the transverse pro-
cess of the axis is ossified separately from the rest of the
vertebra, and remains sometime distinct, as in the Mono-
tremata. In this genus, as in the other carnivorous Marsu-
pials, the inferior lamellae of the transverse processes of the
fourth, fifth, and sixth vertebrae, but especially of the latter,
are particularly large.

Some species of American Opossums (as Didelphvs
Virginia na and its nearest allies) have the spinous processes
of the second, third, fourth, and fifth cervical vertebrae very
high, square, and massive, and being closely applied to each
other by flattened surfaces, form a solid wall of bone along
the top of the neck.

So CERVICAL VERTEBRA. IN THE MAMMALIA. [CH. iv.

In both genera of MONOTREMATA (sub-class Ornitho-
delphia) the cervical vertebrae are seven in number, and in
both the inferior arch of the atlas is completely ossified,
apparently from a separate centre ; but in Ornithorhynchus
a large bifurcated hypapophysis is developed, which is
wanting in Echidna.

In Ornithorhynchus also all the other cervical vertebras
have a single median hypapophysial spine, equally wanting
in Echidna.

In both, the axis has a high compressed spine, and the
odontoid portion remains long distinct from the true centrum
of the bone. In both, the transverse processes are of auto-
genous formation, and remain suturally connected with the
remainder of the vertebra, until the animal is nearly full-
grown (see Fig. 5, p. 25); that of the axis is still distinct in
an adult Ornithorhynchus. Though in this respect they
present an approximation to the Sauropsida (Reptiles and
Birds), they differ from that group, inasmuch as there is not
a gradual transition from these autogenous transverse pro-
cesses of the neck (or cervical ribs, as they may be con-
sidered) into the thoracic ribs, for in the seventh vertebra
the costal element is much smaller than in the others,
indicative of a very marked separation of neck from thorax,
not seen in the Sauropsida. The vertebrarterial canal in
Echidna bruijni is very wide, and passes through all the
vertebrae from the second to the seventh.

CHAPTER V.

SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR
VERTEBRA

IT will be most convenient to consider the vertebrae of
these two regions together.

In Man, there are seventeen trunk vertebrae, twelve
thoracic or rib-bearing, and five lumbar.

The bodies increase in size from before backwards, and
also change their form. The first is like a cervical vertebra,
broad and depressed. They soon become more compressed,
especially at the lower part, so as to be sub-triangular when
seen from one end (Fig. 2, p. 16); after the middle of the
thoracic region they become more circular in outline, and
in the lumbar region they are wide transversely. The ends
of the bodies are flat or slightly concave.

The neural canal does not alter greatly in size throughout
this region, though it does somewhat in form. In the first
vertebra it is wider in proportion to its height than in any of
the others.

The arches have comparatively narrow pedicles arising
from the anterior half of the body, deeply notched behind
for the canal for the exit of the spinal nerves. The lamina
are broad. The spines are moderately long, sub-equal

52 THORACIC AND LUMBAR VERTEBRAE. [CHAP.

throughout the series, rather slender, and sloping backwards
in the thoracic region ; broader (in the antero-posterior
direction) and more upright in the lumbar region, and pre-
senting but scarcely any indication of that convergence
towards a point in the posterior thoracic region so frequently
seen in other Mammals. They are generally simple and
slightly dilated at their ends ; but in the lumbar region, the
posterior edge is often more or less bifid.

The zygapophyses are well developed throughout. In
the thoracic region they are oval, fiat facets, looking pretty
nearly directly upwards (the anterior) and downwards (the
posterior) : the anterior, developed on the top of the pedicle
and projecting forwards, being supported by the " oblique
process ; " the posterior is placed on the under-surface of the
hinder part of the lamina. In the lumbar region, their form
and position change, the anterior having their outer edges
turned upwards, and supported by a short rounded meta-
pophysis (inammillary process). The posterior ones have
undergone a corresponding change, so that their faces, instead
of looking downwards, are directed obliquely outwards ; they
are also much curved.

The transverse processes project throughout the series
from the arch, near the junction of the pedicle with the
lamina. In the greater part of the thoracic region they are
tolerably long, project somewhat upwards and slightly for-
wards, and are dilated and tuberous at the extremities, on
the under-surface of which (except in the two last) they show
a smooth concave facet for the attachment of the tubercle of
the rib. In the posterior part of the thoracic region they
are shorter, and begin to resolve themselves into three dis-
tinct processes, generally conspicuous in the first lumbar.
One of these projects outwards, and, elongating in the second
and third lumbar, it forms the principal transverse process.

v.] PRIMATES. 53

One projects upwards and forwards, by the side of the
anterior zygapophysis ; this is the metapophysis^ or mam-
millary process. The other projects backwards, and
represents in a rudimentary condition the process so largely
developed in many animals called anapophysis. This
gradually becomes smaller in the second and third lumbar
vertebrae, and generally disappears in the fourth.

The lumbar transverse processes are thus not serially
homologous with the thoracic ribs, but with the part of the
transverse process of the thoracic vertebrae to which the
tubercle of the rib is attached, and are complementary to
the ribs, becoming greatly augmented in size directly these
cease. Neither are they normally developed autogenously.1

The sides of the bodies of the thoracic vertebrae bear
facets for the articulations of the heads of the ribs. Except
the last three or four, each vertebra supports a portion of the
head of two ribs, having a large facet near its anterior edge
(placed partly on the body and partly on the side of the
pedicle) for the head of its own rib (i.e. the rib which arti-
culates also with the transverse process), and on the hinder
border of the upper angle of the body a small facet to
receive the anterior edge of the succeeding rib. In the
hinder part of the thoracic region the rib is connected only
with its corresponding vertebra, and not with the one in
front.

Among the remaining Primates, 19 is the prevailing
number of trunk vertebrae, of which usually 12 to 14 bear
ribs. The Gorilla and Chimpanzee (genus Troglodytes),
agree with Man in having 17. The Orang (Simia) has

1 There are several specimens in the College Museum which show
the co-existence, on the first lumbar vertebra, of a rudimentary (supple-
mental) rib, with a transverse process serially homologous with the
transverse processes of the other lumbar vertebrae.

51 THORACIC AND LUMBAR VERTEBRAE. [CHAP.

usually but 16. The Gibbons (Hylobates) and Spider
Monkeys (Ateles) have mostly 18. Among the Lemurina,
Loris and Nycticebus have as many as 23 or 24.

Of thoracic vertebrae, the Gorilla and Chimpanzee have
13, the Orang 12, the Gibbons usually 13 ; other Old World
Monkeys mostly 12 ; the American Monkeys from 12 to 15 :
the Lemurs from 12 to 16.

As a general rule the vertebral column, taken as a whole,
is straighter than it is in Man, showing- a much less marked
sigmoid curve.

Except in the anthropoid Apes, and a few others, the
spinous processes of the anterior thoracic vertebrae lean
backwards, and those of the lumbar and some of the
posterior dorsal vertebras forwards, so that they converge to
a point near the hinder part of the thoracic region, some-
times called " the centre of motion " of the vertebral column.1
This may be between two vertebras, but more often there is
one, which has an upright spine, towards which the others
are directed ; this is the " anticlinal vertebra." It is at this
point that the thoracic vertebrae begin to change their
characters, and assume those of the lumbar vertebrae ; and
the simple elongated transverse processes break up as it
were into the metapophyses, anapophyses, and lumbar
transverse processes, all of which are conspicuous in these
animals.

The transverse processes of the lumbar vertebrae are
usually placed lower on the sides of the vertebras than
in Man.

In Galago the hinder edges of the neural spines of
the lumbar vertebrae bear a pair of backward-projecting

1 This disposition of the spines of the trunk vertebrae is still more
marked in many of the inferior mammals, especially the terrestrial
Carnivora.

v.] CARNIVORA. 55

processes, which clasp the anterior edge of the succeeding
spine. Similar processes are developed, but to a less extent,
in the Howling Monkeys (Mycetes) and in Lagothrix.

The foramina for the exit of the spinal nerves, instead of
being " intervertebral," perforate the pedicles of the arches
in the Potto (Perodicticus). In the same genus, two or three
of the anterior thoracic vertebrae have very long slender
spinous processes, which in the living animal project beyond
the general level of the skin, forming distinct conical
prominences, covered only by an exceedingly thin and
naked integument.

In the CARNIVORA, the trunk vertebrae are nearly always
20 or 21 in number. The genera Felis, Canis, and Viverra
have 13 thoracic and 7 lumbar, Hyana 15 and 5, Mustela,
Nasua, Procyon, and Ursus 14 and 6, Meles 15 and 5 >
Mephitis has the exceptionally high number of 16 and 6;
Mellirora but 14 and 4. Among the Seals, Cystophora, Otaria
and Phoca have 15 and 5, Trichecus and Stenorhynchus
14 and 6.

The spines of the anterior thoracic vertebrae are long and
slender, and slope back to about the eleventh (the antidinai),
after which they are shorter, thicker (from before backwards),
and lean forwards. From this point also metapophyses and
anapophyses become distinctly developed ; the latter are
especially large in the Fdidce. The lumbar vertebra? have
long transverse processes directed forwards and rather
downwards, and short, stout, compressed spinous pro-
cesses.

In the Seals, the trunk vertebrae present much the same
characters, but the anapophyses are usually but slightly
developed, or may be altogether absent, and the spinous
processes show no convergence to a " centre of motion."

Among the INSECTIVORA, the number of the trunk vertebrae

56 THORACIC AND LUMBAR VERTEBRAE. [CHAP.

varies much in the different genera, from 1 8 (13 thoracic and
5 lumbar) in Tupaia, 19 (13 and 6) in Talpa and most
Soricidcz, 19 (14 and 5) in Gahopithecus, 21 (15 and 6) in
Erinaceus, 22 (19 and 3) in Chrysochloris, to 24 (19 and 5)
in Centetes.

There are also great differences- in the development of the
processes of the vertebrae, which appear to accord with the
diversities in the habits and movements of the animal. The
transverse processes of the lumber vertebras are very short
in the comparatively slow-moving, running, or burrowing
Hedgehogs (Erinaceus), Shrews (So rex) and Moles (Talpa),
but they are very long, broad, and inclined downwards in the
jumping Macroscelides and Rhynchocyon, where the lumbar
muscles are greatly developed and the hinder extremities
disproportionately large.

In the Mole, there are distinct, small, oval, flat ossicles on
the under-surfaces of the interspaces between the lumbar
vertebras. Similar ossicles, but in a more rudimentary con-
dition, are occasionally found in the same situation in some
other Insectivora, as the Hedgehog, but not in any other
Mammals.

The usual number of thoracic and lumbar vertebrae in the
CHIROPTERA is 17 or 18, of which from n to 14 may bear
movable ribs. The transverse processes of the lumbar
vertebras are almost obsolete, as are also the spinous pro-
cesses throughout the series.

Among the RODENTIA, the most prevalent number is 19 ;
but it rises as high as 23 (16 and 7) in Capromys, and even
as 25 (17 and 8) in Loncheres.

The characters of the vertebras vary much in the different
genera, as among the Insectivora. In the Hares (genus
Lepus) the anterior thoracic vertebrae have long slender
spinous processes; the lumbar vertebras (see Fig. 3, p. 18)

v.] UNGULATA AND SIREN1A. 57

have very long and slender transverse processes directed
downwards and forwards and widening at their extremities ;
long metapophyses projecting upwards and forwards, small
anapophyses, and remarkably long, single, compressed
median hypapophyses. These latter are not found in the
Rodentia generally.

In the UNGULATA, the bodies of the trunk vertebrae are
generally slightly opisthocoelous. The spinous processes in
the anterior thoracic region are exceedingly High and com-
pressed. The transverse processes of the lumbar vertebra;
are long, flattened, and project horizontally outwards or
slightly forwards from the arch. The metapophyses are
moderately developed, and there are no anapophyses. The
canals for the exit of the spinal nerves frequently pierce the
pedicle of the neural arch (as in the Eland and Cape Buffalo).

In the Artiodactyle sub-order the number of thoracic and
lumbar vertebrae together is almost always 19, though the
former may vary from 12 to 15. Among the Perissodactyles
the number 23 is equally constant, the Horse and Tapir
having 18, and the Rhinoceros 19 thoracic vertebra.

Some species of Hyrax (ff. capensis) have as many as
22 thoracic and 8 lumbar vertebra, making altogether 30,
the highest number in any terrestrial Mammal ; whilst
in Dendrohyrax the numbers are 21 and 7.

The Elephants have 23 in all, 19 or 20 of which bear ribs.

In the order SIRENIA, the thoracic vertebrae are numerous
and the lumbar very few ; thus the Dugong (f/alicore) has
19 thoracic and 4 lumbar, and the Manatee (Manatus) 17
and 2. The bodies are rather triangular, being compressed
and keeled below, and in the young state have no dis-
tinctly ossified terminal epiphyses. The bodies of all the
thoracic vertebrae bear articular facets for the heads of the
ribs. The spinous processes are not very high, but the

58 THORACIC AND LUMBAR VERTEBRAE. [CHAP.

zygapophyses are well developed throughout the series. The
metapophyses are rudimentary, and there are no distinct
anapophyses.

As there is no sacrum in the CETACEA the lumbar re-
gion passes directly into the caudal, and they can only be
distinguished by the presence of " chevron bones " in the
latter.

The thoracic vertebras vary in number from 9 in Hyper-
oodon, to 15 and occasionally 16 in some Fin-Whales
(Balanopterd), and the lumbar vertebrae from 3 in Inia (the
Amazonian fresh- water Dolphin) to 24 or even more in some
of the true Dolphins (Delphinus).

The bodies are short in the anterior part of the thoracic
region, but posteriorly become more or less elongated and
cylindrical. Their terminal epiphyses are strongly ossified
disks, very distinct in young animals, but coalescing com-
pletely with the rest of the body in adult age. The spinous
processes are high and compressed. The zygapophyses are
very little developed, and only found in the anterior thoracic
region. The metapophyses are distinct (see Fig. 20, m],
placed at first near the ends of the transverse processes,
but gradually rising on the arch, are ultimately transferred
to the sides of the anterior edge of the neural spine, from
which they project forwards, clasping between them the
hinder edge of the spine of the vertebra in front.

In most Cetacea the transverse processes in the anterior
thoracic region arise rather high on the side of the neural
arch of the vertebra, but in the hinder part of the same
region become gradually placed lower, until finally they are
transferred to near the middle of the side of the body,
which position they occupy in the lumbar region (see
Fig. 20). The transverse processes of the lumbar vertebrae
are thus evidently serially homologous with the transverse

v.J

CETACEA.

59

processes of the anterior dorsal vertebrae, which, in their turn,
continue backwards the upper series of cervical transverse
processes.

In the Physetfridie. (comprising P/iysekr, Hyptroodon,
Ziphius, and the allied forms) a very different and peculiar
arrangement occurs (Fig. 21). The transverse processes in
the anterior thoracic region (/) are placed quite similarly to

F«<;. ao. — Anterior surface of vertebra: of Dolphin (Globicef>kal*t me/at). ]. A fifth
thoracic ; H seventh thoracic ; i eighth thoracic ; t> first lumbar ; r rib ; m meta-
pophysis ; / transverse process. The dotted lines indicate the position of the
Deuro-central suture.

those of the ordinary Dolphins ; but passing backwards,
instead of changing their position on the vertebrae, they
gradually become smaller, and finally disappear: while,
simultaneously with their diminution in size, other processes
(/) rise from the body of the vertebra, in the situation of the
capitular attachment of the rib, which, rapidly increasing in
length, become continuous serially with the lumbar transverse

6o

THORACIC AND LUMBAR VERTEBRAL [CHAP.

processes. In two or three vertebrae the two co-exist (Fig.
21, B and c), resembling the upper and lower transverse pro-
cesses of the neck, and sometimes even meeting at their
extremities so as to enclose a canal. The lumbar transverse
processes in this case therefore are not serially homologous
with the transverse processes of the anterior thoracic region,

FIG. 21 .—Anterior surface of vertebra; of Sperm Whale (I'/iyseter itmcrocef>hahts), ^ .
A eighth thoracic ; u ninth tlioracic ; c tenth thoracic ; D fifth lumbar ; r rib ;
in rnetapophysis ; / upper transverse process ; /' lower transverse process.

and with the upper transverse processes of the neck, as in the
former case, but rather with the lower transverse processes
of that region ; and yet tried by every other test, the special
homology of the transverse processes of the lumbar vertebrae
of a Dolphin (Fig 20, D /) and a Sperm Whale (Fig. 21, D /)
is perfectly evident.

v.] EDENTATA. 61

The mode of ossification of the thoracic and lumbar
vertebrae of the Cetacea appears, so far as it has been
ascertained, to differ from that of all other Mammals, inas-
much as the neuro-central suture (see Fig. 20) is always
placed a little above the junction of the arch and the body,
the whole of the latter, with any process which may arise
from it, being ossified from the central nucleus. Conse-
quently, in the thoracic vertebne of the Dolphins, the trans-
verse process is anteriorly an outgrowth from the arch, then
partly from the arch and partly from the body, and finally
from the body alone — a condition quite unknown in other
Mammals.

It would appear, from the conflicting statements on the
subject, that the transverse processes of the lumbar region
are sometimes ossified autogenously, and sometimes exo-
gcnously from the centrum.

The members of the order EDKNTATA present some great
peculiarities in the condition of the trunk vertebrae, especially
those of the lumbar region.

As to numbers, the Three-toed Sloths (Bradypus) have
19 altogether (either 16 and 3, or r$ and 4); and the Two-
toed Sloths (C/iola'pus) have sometimes as many as 24 tho-
racic and 3 lumbar, making altogether 27 trunk vertebrae.
The great Anteater (Afyrwecophaga) has 18 (15 and 3.
R. Coll. Surg. ; 1 6 and 2, Mus. Cam.) ; the little Two-toed
Anteater (Cydothurus\ 17 (15 and 2). The Armadillos
have 14 to 16, the Pangolins (Manis) commonly 18 to 21
and the Cape Anteater (Oryctcropus) 21 (13 and 8).

The vertebral column of the Sloths is remarkable for the
extremely broad, flat laminae and short neural spines, lyin
backwards on the next succeeding vertebrae, throughout the
whole column down to the sacrum. All the processes are
very short, and the spines are bifid in the lumbar region.

62

THORACIC AND LUMBAR VERTEX R.E. [CHAP.

In Bradypits a small (anapophysial) process projects
backwards from the hinder edge of the transverse process
of each lumbar vertebra, having on its inner surface a facet,
which articulates with a corresponding facet on the anterior
edge of the arch of the succeeding vertebra, below the
ordinary zygapophysis.

In Megatherium, Myrmecophaga, Cycloturus, and Dasypus
(in fact, all the remaining American Edentates), a disposition
thus slightly indicated in the Sloths, is carried out to a great

l-'lG. 22. - Side view of twelfth and thirteenth thoracic vertebra; of Great Anteater
(Myrmtcophaga, jubata), 3. «/ metapophysis ; tc facet for articulation of tubercle
of rib ; cc ditto for capitulum of lib ; az anterior zygapophysis ; a:1 additional
anterior articular facet ; pz posterior zygapophysis ; pz1 and pz- additional pos-
terior articular facets.

extent, and results in a very complex and altogether peculiar
method of articulation between the vertebrae.

It will be most convenient to describe it from one species,
the Great Anteater (My rmecophaga jubata), but it is the same
in principle in all the above-named genera.

The anterior thoracic vertebrae articulate in a perfectly
normal manner by large anterior and posterior zygapophyses.
These retain the horizontal position of their facets through-
out. On the eleventh dorsal vertebra, the upper surface of
the backward projecting process which bears the posterior

v.]

EDENTA TA.

zygapophysis (pz) below, develops an articular surface
(/z1) which looks upwards and articulates with a corre-
sponding downward directed process (azl) developed on the
upper part of the arch of the following vertebra, rather
below the metapophysis (///). Thus the vertebra has a
process projecting backwards, with flattened articular facets
on its upper and under surface, fitting into a deep recess
on the anterior edge of the arch of the vertebra behind,

FIG. 23. — Posterior surface of second
lumbar vertebra of Great Anteater, §.
/ transverse process ; pz posterior
zygapophysis ; /s1, fzj. and /z3. ad-
ditional posterior articular Cicets.

FIG. 24. — Anterior surface of third lum-
bar vertebra of Great Anteater, j.

articular facets.

and the articulation is now by two zygapophysial surfaces
on each side of the arch instead of one.

In the thirteenth ' thoracic vertebra a third articular facet
(PZ*) is developed on the hinder margin of the lamina of
the arch, still higher than the last additional one (f>zl),
and separated from it by a deep notch. This looks mainly
outwards, and articulates with a corresponding facet (az 2,
Fig 24) on the anterior edge of the arch of the fourteenth

1 In the Cambridge specimen this description applies to the fourteenth
and fifteenth vertebrae respectively.

64 THORACIC AND LUMBAR VERTEBRAE. [CHAP.

vertebra, placed to the inner side of the metapophysis, which
is now situated on a process projecting forwards into the
notch between the two upper articular facets of the antece-
dent vertebra. So that there are now three distinct articu-
lations connecting the arches of the vertebraj on each side,
the processes of the vertebrae which bear them interlocking
in a " tenon and mortise " fashion.

This condition continues as far as the second lumbar, in
which, in addition to these three facets, a fourth (ps 3 is)
developed on the under-surface of the hinder edge of the
transverse process near its outer extremity, which articulates
with a similar facet (az 3) on the upper-surface of the
transverse process of the third lumbar, so that there are now
four pairs of articular facets, or zygapophyses, on each arch.
The same occurs also between the third lumbar and the
first sacral vertebra.

In the Armadillos the lumbar metapophyses are very long,
and project upwards, outwards, and forwards, supporting
the bony carapace, while the broad transverse processes are
exceedingly reduced.

An allied extinct genus, Glyptodon, had the greater number
of the trunk vertebrae completely ankylosed, a condition
altogether unique in the Mammalia.

In neither of the Old World Edentates, Mam's and
Orycteropus, is there any development of the articular facets,
other than the ordinary zygapophyses. In the former genus
the metapophyses (contrary to the usual rule) project rather
backwards than forwards. The anterior zygapophyses of the
lumbar and posterior thoracic regions are largely developed)
and very concave, completely embracing the semicylindrical
surfaces of the posterior zygapophyses. There are no
distinct anapophyses. In Orycteropus the lumbar vertebra?
are numerous (8), with carinated bodies, long and slender

v.] MARSUPIALIA. 65

spines inclined forwards, long, broad, and flat transverse
processes pointing forwards and downwards, well developed
metapophyses and rudimentary anapophyses.

In the MARSUPIALIA, the number of thoracico-lumbar
vertebras is invariably 19, although there are some apparent
exceptions, in which the last lumbar assumes the form of a
sacral vertebra. The rib-bearing vertebrae are always 13,
except in the Koala (Phascolantos), which has but 1 1, and one
species of Wombat (Phascolomys vombatus), which has 15.
The Hair)-- nosed Wombat (P. latifrons) has the ordinary
number.

In the Kangaroos, the lumbar vertebras have largely
developed metapophyses and anapophyses, and moderate-
sized transverse processes much curved forwards.

In the running and jumping Bandicoots (Perameles) the
lumbar vertebrae have very slender, long, forward -directed
spines, and long transverse processes. In the climbing
Opossums (Didt'lphys), on the other hand, the spines are
very short and broad from before backwards.

The MONOTREMATA agree with the Marsupials in the total
number of trunk vertebrae, but those that bear ribs are more
numerous, viz. 16 in Echidna, and 17 in Ornithorhynehus.

The spinous and transverse processes are very short,
and the ribs have no articulation with the latter, but are
attached to the bodies only, the greater part of the articular
surface being below the neuro-central suture, the reverse of
what occurs in the higher Mammals. In the thoracic ver-
tebrae the canals for the exit of the spinal nerves perforate
the neural arch.

CHAPTER VI.

SPECIAL CHARACTERS OF THE SACRAL AND CAUDAL
VERTEBR/E.

Sacral Vertebra. — The difficulties in defining the sacral
vertebras have been noticed at page 30. Their essential
character is best illustrated by tracing it up from the simple
condition it presents in the tailed Amphibians (as Menopoma).
In these animals a series of similar small straight ribs are
movably articulated to the ends of the transverse processes
of all the trunk vertebra;, which are not distinctly divisible
into separate regions. To the distal extremity of one of
these the ilium is attached. This vertebra with its rib thus
constitutes the "sacrum," and the ilium is clearly seen not
to be a " pleurapophysis," as it is sometimes called, or any
part of a vertebra, but a something distinct and superadded.
In the Crocodiles there are two vertebras with strongly
developed rib-like bones connecting them to the ilium, and
remaining long only suturally united to their vertebras.

The inferior ossification of the transverse processes of the
true sacral vertebras in Mammals (see Fig. 6, p. 26) is clearly
of the same nature, though more rudimentary in character,
and coalescing at an earlier period with the remainder of the
vertebras. It is not yet known that it exists in all Mammals,

CHAP, vi.] SACRAL VERTEBRAE. 67

but this may be considered probable, as it is certainly found,
at least in the first sacral vertebra, in such different forms as
Man, the Chimpanzee, Orang, Cat, Sheep, Elephant, Sloth
and Wombat.

The ankylosis ot additional vertebrae in the Mammalia is
probably related to the greater fixity and more complete
attachment of the pelvis to the vertebral column in this class ; l
for the innominate bone is not only articulated by its iliac
portion to the true sacral vertebne, but it has also a posterior
connection with the vertebral column by its ischial portion,
by means either of very strong ligaments, or in some cases
by bony union.3

In Man there are usually five ankylosed vertebrae, con-
stituting the " os sacrum " of anthropotomy, but only two, or
sometimes three, have distinct costal elements. The re-
mainder may be called pseudo-sacral, and belong more pro-
perly to the caudal series. The sacrum as a whole is broad,
strongly curved in the longitudinal direction, with the con-
cavity downwards, and its anterior extremity forms with the
body of the last lumbar vertebra a more prominent " sacro-
vertebral angle " than in other Mammals.

In the Gorilla, Chimpanzee, and Orang, there are
generally five ankylosed vertebrae, to which the last lumbar
not unfrequently becomes united in old animals. The whole
sacrum thus formed is long and narrow, gradually tapering
posteriorly, and much less curved than in Man. In the
other Monkeys, there are usually two or three, rarely four,

1 This is carried to a still greater extent in birds.

a Hence the following definition of the sacrum : " The posterior
limit of the sacral region is characterized, not by the union of the
different osseous pieces, which varies according to age, but by the place
of insertion of the ischio-sacral ligaments." (A. MILNE EDWARDS,
Famille Jes Chtvrotains, p. 52.)

F 2

68 CAUDAL VERTEBRA. [CHAP.

ankylosed vertebrae ; the first two, or true sacrals, are broad .
and behind these the sacrum suddenly contracts.

In the Lemurina the number of united vertebrae varies
from 2 to 5.

In the CARNIVORA, there are generally few true sacral
vertebrae, only 2 in the Puma, Proteles, and Hyena. 2 or 3 in
the Tiger ; in the Bears and Seals as many as 4 or 5 may
be united by bone in old animals. In the Dog there are
usually 3 ankylosed vertebras.

In most UXGULATA and RODF.NTIA the sacrum consists of
one broad vertebra joining the ilia, and a series of narrow
ones, varying in number with age, gradually diminishing in
width, ankylosed to it behind.

In the Beaver among Rodents, most Chiroptera, the Cape
Anteater (Oryderopus) among Edentates, and the Wombat;
among Marsupials, the sacrum consists of numerous anky-
losed vertebrae, with widely-expanded transverse processes,
which are longer in the hindermost vertebrae, and nearly
meet the ischia.

In most other EDENTATA, as the Sloths, Anteaters,
Armadillos, and in Pteropus among Chiroptera, this modi-
fication is carried further, and the transverse processes of the
hinder pseudo-sacral vertebrae form a complete bony union
with the ischia, converting into a foramen what is usually
the sacro-sciatic notch. In some of the Armadillos as many
as 10 vertebrae are thus firmly fused together, and with the
innominate bones.

In MARSUPIALIA usually but one vertebra supports the
iliac bones, though another is commonly ankylosed with it.

In the MONOTREMATA, the Ornithorhynchus has 2
ankylosed sacral vertebrae, and the Echidna 3 or 4.

The CETACEA having no iliac bones, have no part of the
vertebral column specially modified into a sacrum : but in

VI.]

CAUDAL VERTEBRAE.

69

the SIRENIA, the rudimentary ilia are attached by ligament
to the end of the transverse processes of one vertebra, which
may hence be regarded as sacral.

Fie. 35.— Anterior surface of third caudal vertebra of Leopard (Felit tfofiantia), |.
<u anterior zygapophysis ; /i posterior zygapophysis ; m metapophysis ; / trans-
verse process

Caudal Vertebra. — The vertebrae of the tail vary greatly
in number and in characters in different animals. When it
is well developed, as, for example, in the long-tailed
Carnivora, from one of which the accompanying figures are

FIG. a6 — Upper surface of the third caudal vertebra of I/eopard, |. a* anterior
zygapophysis ; /* posterior zygapophysis ; m metapophysis ; / transverse process.

taken, the anterior vertebrae (Figs. 25 and 26) are com-
paratively short and broad, with complete neural arches,
though without distinct spines, prominent metapophyses,
and anterior and posterior zygapophyses (the latter especially

yo

CAUDAL VERTEBRAE.

[CHAP.

being raised on pedicles), and well-developed single transverse
processes. But a gradual change takes place in these
characters (see Figs. 27 and 28), the body lengthens out and
becomes more and more cylindrical ; the neural arch
diminishes and finally disappears, leaving for a while a pair
of processes at each extremity of the vertebra, the remains
of the parts of the arch which bore the xygapophyses ; the
transverse process is much reduced, and confined to the

FIG. 27. — Anterior surface of twelfth
caudal vertebra of Leopard, jj. tit
metapophysis ; p processes serially
continuous with those which support
the posterior zygapophyses in the an-
terior vertebrae ; /; hypapophyses. The
process on the side of the body be-
tween MI and k is the anterior trans-
verse process.

FIG. 28.— Upper surface of twelfth caudal
vertebra of Leopard, 5. in met:ipo-
physes ; p processes serially continuous
with those which support the posterior
zygapophyses in the anterior vertebra;.
t transverse process ; t' anterior trans-
verse process.

posterior extremity of the body, a second one appearing at
the anterior extremity. Even these rudiments of processes
gradually cease to be perceptible, and nothing is left but a
cylindrical rod of bone, representing the centrum alone of
the vertebra. These diminish in size towards the apex of
the tail, the last being usually a mere rounded nodule.

Connected with the under-surface of the caudal vertebrae
of many animals which have the tail well developed are

VI.]

GENERAL CHARACTERS.

certain bones, formed more or less in the form of an in-
verted arch (Fig. 29), called chci'ron bones (French, Os en V ;
German Untere Bogen ; hamapophyscs, Owen). These are
always situated nearly opposite to an intervertebral space,
and are generally articulated both to the vertebra in front and
the vertebra behind ; but sometimes chiefly or entirely either
to one or the other. They are usually articulated movably
to prominences (hypapophyses) on the lower surface of the
body of the vertebra, but occasionally become ankylosed to

FIG. 29. — Anterior surface of fourth caudal vertebra of Porpoise (Pkoffna com-
munis), J. i spinous process ; m mctapophysis ; / transverse process ; ft chevron
bone.

it. They ossify from two centres, one on each side, which
usually coalesce in the median line below, though not un-
frequently, especially at the beginning and end of the series,
where they are less developed, the two lateral portions remain
permanently separate. They serve to give a larger surface of
attachment for the inferior muscles of the tail, and also to
protect the caudal vessels, which nin within the canal formed
by the series of these bony arches. They are always best

72 CAUDAL VERTEBRA. [CHAP.

developed near the anterior extremity of the tail, and are
never found under the posterior rudimentary vertebrae.

In Man the caudal vertebrae are quite rudimentary ;
usually 4 in number, all ankylosed together, and constituting
the coccyx, or oscoccygts, of anthropotomy. The first is some-
times ankylosed to the sacrum.

Among the Simiina there are but 4 to 5 caudal vertebrae
in the Anthropoid Apes and in the Barbary and Black
Macaques, no more than 10 in some Baboons, and as many
as 32 in Semnopithecus, and 33 in some of the Spider Mon-
keys (Ateles).

In the latter the tail is prehensile, and the vertebra; are
broader and altogether more strongly developed than in the
weak, pendant, though almost equally long tails of the Old
World monkeys.

Chevron bones are found in all except those species that
have the tails quite rudimentary. They are most fully de-
veloped in Ateles, where the extremities are often bifurcated.
They are attached to a pair of projections on the anterior
end of the lower surface of the vertebra.

In the Lemurina, the number of the caudal vertebrae
varies from 7 to 29.

Among the CARNIVORA, the Bears have very short tails,
with from 8 to 10 vertebras, the Seals from 9 to 15 ; some
of the Lynxes have but 13, but most of the animals of the
order have tails of moderate or great length ; the greatest
number of vertebrae being found in Paradoxurus, which
may have as many as 36.

Chevron bones are usually not much developed ; they
are articulated (sometimes ankylosed) to the front ends of
the vertebrae, as in the Primates.

In the INSECTIVORA, the tail is very variable. It is short
and simple in Erinaceus and Centetcs, long in Galeopithecus.

vi.) RODENT1A. 73

Solenodon, Gymnura, Potamogalc^ Aficrogale (43 vertebrae),
Tupaia and Rhynchocyon ; in the last-named genus the
chevron bones are well developed and bifid.

In the CHIROPTF.RA, the tail is sometimes exceedingly
rudimentary, as in Destnodus and Pteropns ; sometimes elon-
gated, but composed of long, simple, slender, cylindrical
vertebral bodies ; and generally enclosed in the interfemoral
cutaneous expansion.

Among the different members of the order RODENTIA,
there are great differences in the condition of the caudal
vertebrae.

In the Hares, Guinea Pigs, Capybara, &c, the tail is
almost rudimentary. In the Cape Jumping Hare (Ptdetes)
it is nearly as long and powerful as in the Kangaroo, and
has well-developed chevron bones.

In the true Porcupines the tail is generally short ; but in
some allied genera (Tree Porcupines) it is much elongated
and prehensile.

In the lleaver (Castor) there are 24 caudal vertebrae, all
short, broad, and depressed, and with wide transverse pro-
cesses, becoming double (anterior and posterior) about the
middle of the tail, not by development of a new process,
but by gradual division of the one existing in the anterior
region.

In the UNGULATA, the tail is variable in length, but of
simple character and function ; it is never prehensile,
nor has it ever chevron bones, although occasionally, as
in the Ox, a pair of well-developed hypapophyses may be
produced so as to meet in the median line, enclosing a
small canal.1 The vertebrae are most numerous (about 16

1 The Eocene Anoplotherium appears to have had chevron bones
beneath the vertebrae of its long tail.

74 CAUDAL VERTEBRAE. [CHAP

to 20), in the Oxen and in some Antelopes (Koodoo), and
least so in some Deer, especially Moschus, in which animal
the tail is quite rudimentary.

The Elephant has a long tail, composed of 31 vertebras
of simple character, without chevron bones.

In the Hyrax the tail is short, consisting of about 4 to 9
vertebrae.

As the tail is the principal organ of locomotion in the
CETACEA, it is always very well developed, and consists of
numerous (from 18 to 30) vertebrae.

Chevron bones are always present, and of simple character,
though with long compressed median spines (see Fig. 29,
p. 71). They are mainly attached to the posterior extremity
of the vertebra immediately in front of them.

The characters of the caudal vertebra in the various
animals of the order are tolerably uniform, the tail having
the same function in all. In the anterior part of the region
the bodies are very massive and cylindrical ; the arches have
high spines, with metapophyses on their anterior edges, and
the transverse processes are tolerably long, and directed
straight outwards. In passing backwards the arches and all
the processes gradually disappear, and the bodies become
much compressed, and elevated vertically. Suddenly a
change takes place (at the spot where the end of the
vertebral column becomes enclosed in the horizontal,
laterally extended cutaneous expansions, constituting the
" flukes " of the tail,) and the vertebrae altogether alter
their characters, becoming much smaller, wide transversely
and depressed. There is always one vertebra which is
transitional in its character between these two forms. Most
of the caudal vertebras are perforated by a vertical canal on
each side, either passing through the base of the transverse
process, or in the posterior vertebrae through the body of

vi.] EDENTATA. 75

the vertebra itself. This transmits an ascending branch of
the caudal artery.

The SIRENIA have numerous, much depressed caudal
vertebra, with wide transverse processes, gradually dimin-
ishing in length to about the 15th vertebra from the end.
The processes then widen again, to decrease once more
towards the end of the tail, thus corresponding more or less
with the shape of the caudal fin. They are thus very different
from those of the Cetacea.

Among the EDENTATA, the Sloths have a quite rudi-
mentary tail, consisting of from 6 to 10 depressed vertebrae
without chevTon bones.

FIG. 30. — Anterior surface of third caudal vertebra of Great Armadillo (Priotion
jfifai), }. t spinous jmxres-, ; m metapophyiis ; at anterior zygapophysis ;
I transverse process ; h chevron U.ne with diverging processes.

In the allied Megatherium the tail was greatly developed,
with long processes and large chevron bones, as is the
case with nearly all the Entomophagous Edentates, but
mostly so in the Pangolins (Mam's), one species of which
(M. macrura] has 46 to 49 tail vertebrae, the highest number
known in any Mammal. Cydoturus has a prehensile tail
of 40 vertebrae. The little Chlamydophorus has a rather
short tail of 15 vertebras, remarkable for being expanded,
depressed, and spatulate towards the end, the transverse

76 CAUDAL VERTEBRA. [CHAP.

processes increasing in size instead of gradually diminishing,
as is almost universally the case.

The chevron bones are usually much developed. They
are Y-shaped, having long, simple, compressed spines in
Orycteropus ; V-shaped in Manis and most Armadillos ; but
in Priodon (Fig. 30) they have wide, diverging, lateral pro-
cesses, instead of a median spine. They are attached
rather to the vertebra in front than to that behind them.

In the MARSUPIALIA, as might be supposed in so hetero-
geneous a group, there is great diversity in the condition of
the caudal vertebrae.

In the Wombat (Phascolomys) and Koala (Phascolarctos)
the tail is comparatively rudimentary.

In the Kangaroo, on the other hand, it is very large, and
serves as an organ of support when standing upright. It is
composed of 2 1 to 25 vertebrae, the first few with short bodies
and large processes ; afterwards the bodies lengthen out, be-
coming cylinders contracted in the middle. The zygapophyses
soon cease, but the metapophyses continue longer. The
neural arch is not continued longer than about the middle
of the tail ; the transverse processes are gradually placed
further and further back on the vertebra, and then anew one
arises near the anterior end, so that they become double.

The chevron bones are placed quite between the verte-
brae, so that it is difficult to say to which they most
properly belong. In the proximal part of the tail their
free edge is compressed and develops a process forwards
and backwards, giving a hatchet shape when seen side-
ways. Further back they also send out broad processes
laterally, so as to be cruciform, with a flat inferior surface.

In some Marsupials the tail is prehensile, as in the
Opossums (Didelphys), with from 19 to 35 vertebrae, and the
Phalangers (Phalangista) with from 21 1031.

vi.] MONOTREMATA. 77

Chevron bones are generally present in the tails of all the
Marsupials, except the Wombat and Koala. In the Thylacine
they are few, and comparatively rudimentary.

The tails of the two forms composing the order
MONOTREMATA differ considerably.

The Echidna has 12 caudal vertebrae. These have no
hypapophyses, but there are two single median chevron
bones near the middle of the tail, more like the lumbar
subvertebral ossicles of the Mole than ordinary' chevron
bones. The Omithorhynchus has 20 or 21 caudal vertebra,
with single median hypapophyses, no chevron bones, and
wide transverse processes which increase in length towards
the middle of the tail, being shortest near the sacrum and
end of the tail.

The following Table, showing the number of vertebrae in
a very large series of Mammals, is mainly taken from the Cata-
logue of the Museum of the Royal College of Surgeons of
England.1 Those distinguished by an asterisk (*) are from
the collection of the University of Cambridge, and have been
added to make the list still more complete. The + after the
number of the caudal vertebrae indicates that the termina-
tion of this region (as too often happens with mounted
skeletons) was defective. The others are presumed to be
complete or very nearly so.

In compiling this list the following rules have been
observed : The cervical vertebrae are those in front of the
first which bears a rib directly articulating with the sternum.
The thoracic or dorsal vertebrae are those which bear

1 Catalogue of the Specimens illustrating the Osteology and Dentition
of Vertebrated Animals recent and extinct, contained in the Museum of
the Royal College of Surgeons of England, part ii. Class Mammalia, other
than Man, by \V. H. Flower, assisted by J. G. Garson. London, 1884.

NUMBER OF VERTEBRA.

[CHAP.

movably articulated ribs. The lumbar vertebrae are those
that intervene between the thoracic and sacral regions. The
artificial and conventional definition of the sacral vertebrae
as those that are ankylosed together in the adult state to
form a single bone has been generally adopted in default of
a more scientific one of universal application. In the
Cetacea, the first caudal is that which bears upon its hinder
edge the first pair of chevron bones.

It must never be forgotten that although the division of
the vertebral column into distinct regions is convenient for
descriptive purposes, at the contiguous extremities of the
regions the characters of the vertebrae of one region are
apt to blend into those of the next, either normally or as
peculiarities of individual skeletons.

PRIMATES.

Cervic.

Thorac

Lumb.

Sacral.

Caudal.

Homo sapiens

7

12

c

c

•J A

Troglodytes ni^er

7

I \

A

c

C

Gorilla savagii

7

I ^

A

c

A

Simia satyrus . .

7

12

c

A

Hylobates syndactylus
* lar

- 7
7

'3

IT.

4
e

4

A

4
-}

Colobus vellen>us. .

7

12

7

-1

'O

Semnopithecus entellus

7

13

6

32

schistaceus .
cristatus
Nasalis larvatus

• 7

•- 7
7

12
12
12

7
6

3
3

17 +

27

Cercopithecus patas

7

12

7

i

28

sabaeus ...

7

IT.

6

2

albigularis ...
petauri.-ta ...
Macacus cynomolgus

• 7
• 7
7

12
12
12

7
6

3

2
7

19 +
26

7

12

7

2O +

pilentus ...

7

12

7

^

2A

sinicus

7

12

7

7.

22

rhesus

7

12

7

•2

18

nemestrinus .

7

12

7

17

inuus

7

12

7

7

•j +

i

VI.]

IN VARIOUS MAMMALS.

79

Primates.

Cervic Thormc

I.umb.

Sacral.

Caudal.

Theropithecus gelada

7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7

7
7
7
7
7
7
7
7

»3
»3
13
'3

12
12
»3
'3
'4
'4

14

'4
»5
13
13
'3
'3

12

'3

12

'3

12
13
13
13

'3
'4
16

'7
'5
'5
13
»3

13
13
13
»3
'3
13
13
13

6
6
6
6

7
6

6
6
5
4
4
7
6

6

Q

9
8
6

>•

7
7
7
6
6
9
7
6

6

6
6

7
7
7
7
7
7
7
7

3
3
3

2
2

4
3
3
3
3
3
3
3
3
3
3
3
4
3
3
3
3
3
3
3
3

2

3
3
3
3
3
3

3
3
3
3
3
3
3
3

26
20
23
I4 +

r

23
24
25
31
29
27
23
27
25
23

9
23
27
27

27
28

24
25

21

7

12
12
20
9
27
27

19 +

25
23

18 +

19
20

22
3

Cynoccphalus babouin

anubis . .

porcarius

leucopha-us —
maimon
Chrysothrix sciurea

Cebus capucinus

Ateles geoflfroyi

Lagothrix humboldtii

Nyctipithccus vociferans
Pithccia monachus ....

Mycetes seniculus . .

Midas oedipus

Hapale jacchus

Indris brevicaudatus

Avahis laniger

Hapalemur griseus .. .

Lemur varius

mongoz

Chirogaleus furcifer

pusillus

Galago crassicaudatus . .

allcni

Loris gracilis

tardigradus

javanicus

Perodicticus potto

calabarensis
Tarsius spectrum

Chiromys madagascaricnsis . . .

CARNIVORA.
FcHs leo

tigris

pardus

onca

chrysothrix

catus

domestica

manx variety

8o

NUMBER OF VERTEBRAE.

[CHAP.

Carnivora.

1

Cervic.

Thorac.

Lumb.

Sacral.

Caudal.

Felis caracal

7

J3

7

3

II +

lynx

7

13

7

3

14.

Cynselums jubatus

7

13

7

3

22

7

13

7

7

2Q

7

n

7

7

in +

Genetta tigrina

7

1 1

7

2

2Q

Hemigalea hard wick i

7

14

6

3

26

Paradoxurus musanga
Arctictis binturong

7

7

13
14

7
c

3

7.

25

7/1

7

14

6

7

74

Eupleres goudoti

7

13

7

2O

Galidia elegans

7

13

7

7

!

10+ '

Herpestes griseus

7

13

7

7

21

Crossarchus obscurus

7

14

6

2

IQ

Suricata tetradactyla

7

15

6

7

2O

7

14

6

7

2O

Proteles cristatus

7

15

c

2

24

* ,, ....

15

c

2

26 +

Hysena bruncea ....

7

16

4

crocuta

7

15

c

TO

Lycaon pictus

7

13

7

7_

144

Icticyon venaticus .

7

IT,

7

7

T4

Canis javanicus

7

17

7

7

17

prinicevus

•7

I 7

7

•2

16

familiaris (Dingo)
(Newfoundland)

7
7

13
17

7
8

3

19

174-

(mastiff) . .

7

17

8

27

(German boarhound) ...
(French bloodhound) ...
(deerhound)

7
7
7

H
13
13

7
7
7

3

7

20
20
2O

(greyhound) .

7

17

7

IO

(retriever)... .

7

17

7

7

IO

(Skye terrier) .

7

17

7

•I

IO

(bulldog)

7

17

7

7_

20

*Canis lupus

7

17

7

20

vulpes . ..

7

17

7

7

21

7

6

lagopus

7

17

7

•3

*y

procynoides

7

14.

6

r e 4-

Otocyon megalotis

7

17

7

7

Mustela martes . .

7

14

6

5

in-4-

zibellina

7

14.

6

7

16 +

putorius

7

6

18

7

I c

6

|C

VI.J

IN VARIOUS MAMMALS.

81

Carnivora.

Cervic.

Thorac.

Lumb.

Sacral.

CaudaL

Mustela siberica

7

6

•1

21

erminca

7

Id

6

7

18

7

1 :

6

2

vulgaris

7

1C

6

7

16

7

6

7

I r

7

I ;

e

7

Clulo luscus

7

1 ;

c

7

I c

(ialictis vittala

7

16

c

7

21

Mellivora indica

7

id

I r

Taxidea arnericana

7

1 ;

c

7

16 +

Meles taxus .

7

1C

c

iS

7

Id

5

7

Mydaus mcliccps

7

ixi

6

7

Q +

Arctonyx collaris

7

16

2O

Mephitis mcphitica

7

16

6

2

21

Lutra vulgaris

7

id

6

2

26

7

id

6

2C

7

id

6

7

2O

* lalandi

7

1C

^

22 +

Enhydra lutris

7

Id

6

21

7

Id

6

10 +

Procyon loior

7

Id

6

7

18

Nasua rufa

7

Id

6

2 — \

10 +

Bassaris astuta

7

I •!

7

\

23

Cercoleptes candivolvulus ...
Ailurus fulgens

7

7

U
Id

6
6

3

7

26—29
18

7

'4

<;— 6

\

10 +

tibetanus

7

15

c

C

arctus

7

Id

6

C

7

id

4

Q +

j

14

left side

}'

L

10+

7>

7

. »S.

nghtside

Id

Ij

\

6

7

Id

6

e

7

1C

c

c

7

1C

r

IO

7

1C

f

1 1

PlNNIPEDIA.

Otaria jubata

7

1C

c

8

•

7

1C

c

A

9 +

82

NUMBER OF VERTEBRAE

[CHAP.

Pinnipedia.

Cervic

. Thorac

. Lunib.

Sacral.

Caudal.

Otaria stelleri

7

15

5

4

14

* ,,

,)

16

left sidi

-!J4

\

(s

12

californiana

7

15

rightsid

15

« \i

e.

r

-5

IO

australis

7

15

c

4

IO

ursina

15

c

1 1

Trichechus rosmarus

7

14

6

8 +

* »

7

14

6

A

12

Halichocru^ °rypus

7

I C

;

Phoca vitulina

7

15

c

A

12

hispida

7

15

e

I c

7

15

c

I T.

grcrnlandica .

7

1C

r

i e

Stenorhynchus leptonyx
carcinophagus
Cystophora cristata

7
7
7

14
15

15

6

5
c

3
3

14
12

Macrorhinus leoninus

7

15

q

I i

UNGUI.ATA.
Bos taurus ...

7

13

6

c

TO

*Bos primigenius

7

13

6

c

"Bubalus depressicornis

7

13

A

18

* caffer

7

IT.

6

A

18

Bison americanus .

7

14

c

C

174- :

* »

7

14

c

C

i r

bonasus

7

14

r

A

17

*Ovibos moschatus. . .

7

I :

c

6

Ovis aries

7

17

7

41

7 4-

musimon

7

I 7

6

nahoor

7

1 1

6

tragelaphus ...

7

13

6

Capra ibex

7

17

6

hircus

7

17

6

Boselaphus tragocamelus
Gazella dorcas

7
7

13
17

6
6

5

1 J

Saiga tartarica

7

T3

6

Tetraceros quadricornis
Connochaetes tmu...

7
7

13

14

6
6

4

8 +

Antilocapra americana

7

1^

6

14-t-

VI. J

IN VARIOUS MAMMALS.

Ungulata.

Corvic. Thorac.

GiraflFa camelopardalis 7 14

7 «4

Moschus moschifcrus ... 7 14

7 »3

Cervulus muntjac \ 7 13

Ccrvus davidianus ! 7 13

canadcnsis 7 13

clcphus 7 13

damn ] 7 13

hibcrnicus 7 '3

Rangifer tarandus 7 14

.. 7 '4

Alces machlis J 7 13

Capreolus caprea 7 13

Hydropotes inermis 7 12

Cariacus mexicanus 7 13

Pudua humilis 7 13

Tragulus javanicus 7 13

Camel us bactrianus 7 12

dromedarius 7 12

Auchenia glama 7 12

7 '2

pacus 7 I2

vicugna 7 12

Dicotyles tajacu . 7 14

.. 7 H

„ 7 '4

Sus cristatus 7 13

scrofa 7 '4

„ 7 M

Babirussa alfurus j 7 13

Phacochrerus africanus 7 13

Hippopotamus amphibius — 7 15

,, 7 15

Tapirus indicus 7 18

amcricanus 7 18

Equus caballus 7 18

„ 7 18

.. 7 ' '9

„ 7 19

asinus 7 '°

zebra ' 7 > 18

Rhinoceros unicornis 7 '9

sumatrensis 7 19

Lumb.

SacraL Caudal.

5

5

6
6
6
6
6
6
6
5

6
6
6
6
6
6
7
7
7
7
7
7
6

5

6

6

6

5

•i
4
5
S

6
6

I

3
3

4
3
5
5
4
4
4
4
4
5
5
4

6

4
4
5
5
4
4
5
4
5
4
4
4
5
4
4
4
4

2

6
8
6
6
6
6
5
5
5

6

12

20

6
7

14 +

'3

11

ii
n

10 +
8
10

'3

8

13
'5 +
'3 +
'3 +

9 +
'3
14

7

7

24

21

24

23

u +

13

12

'5 +

'7

21 +

22

NUMBER OF VERTEBR/E

[CHAP.

Ungulata.

Cervic.

Thorac.

I.umb.

Sacral. Caudal.

Rhinoceros sumatrensis
Myrax capensis

7
7

20
22

3

8

4
7 4

Dendrohyrax arboreus

7

21

7

6 7 +

dorsalis

7

21

7

6 8

Elephas indicus

7

2O

7

4. 3O +

7

iq

C

4. —

7

IQ

4

4. 24.

t africanus .

7

IQ

4

C 24 +

SlRENIA.
Halicorc dugong

7

iq

4

27

7

18

4.

20 +

' '

7

19

§

27

Manatus anicricanus

6

17

2

27

senegalensis ... .

6

17

2;

CETACEA.
Baltena mysticetus ...

7

12

14

22

australis

7

1C

IO

2=;

Bala;noptera rostrata

7

1 1

12

IQ

Physeter macrocephalus
Hyperoodon rostratus

7
7

II

q

8

IO

24

iq

Mesoplodon grayi

7

IO

12

IQ

Berardius arnuxi

7

IO

12

IQ

Platanista gangetica...

7

IO

q

26

Monodon monoceros

7

1 1

6

26

7

12

7

24

Delphinapterus leucas

7

1 1

9

22

Phocrcna communis

7

13

^2

7

12

14.

7O

Orca gladiator

7

1 1

IO

23 +

Pseudorca crassidens .

7

IO

q

23

7

IO

II

TJ

Globicephalus melas

7

II

17

28

Tursiops tursio

7

13

16

27

7

12

17

Sotalia sinensis

7

12

q

23

VI.]

IN VARIOUS MAMMALS.

Cetacea.

Ccrvic.

Thorac.

Lurnb.

Sacra] . Caudal.

Lagenorhynchus acutus
alhiroitris

7

7
7
7
7

7
7
7
7
7
7
7
7

•]

7
7

?

7
7

I

7
7

I
I

7
7
7
7
7
7
7
7

'5

14
'5
14
14

12
12

13
12
12

12

13
12

14
'3
14
13
13
'3

'3
'3
'3
'3
14
•3
'3
»3
13
13
13
15
14

12
12

13
12

'3
12

20 ! 35 +

V -

21
21
2O

7
7
6

7
7

7
7

I

7
6
6
6
6

I

6
6
6
6
6
6
6
6

1

5
6

6

7

67
3

3
3
3
3
3
4
3
4
3
4
3
4
4
4
4
4
4
4
4
4
4
4
4
4
5
4
4
5
4
4
4
3

32
32
34

16 +

21
24
25
2O

17

16
24
24

22
30
'7

32 ;
27
26

20 +
30

20+ '
25 +
20 +

10 +
10

6
18
14
5 +
«7
35
23
3i
30

Delphinus delphis.

RODENTIA.
Sciuropterus volucclla

Sciurus vulgaris

indicus

Tamias asiaticus

Spermophilus mongolicus ...
Cynomys ludovicianus

Arctomys marmotta

Castor canadensis

Muscardinus avellanarius
Hydromys chrysogaster
Cricctus frumcntarius

Mus rattus. ... ....

dccumanus

fuscipes

musculus

minutus

Hapalotis albijxrs

Fiber zibcthicus

Avicola amphibius

agrestis

Myodes lemmus

Ellobitis talpinus

Spalax typhlus

Khizomys pruinosu1*

Bathycrgus maritimus

Gcorychus capensis

Geomys bursarius .

Xapus hudsonicus .

Dipus sagitta

Alactoga jaculus

Pedetes caffer

86

NUMBER OF VERTEBRAE

[CHAP.

Rodentia.

Cervic

i Thorac.

Lumb.

Sacral.

Caudal.

7

12

7

4

25

7

13

6

4

19 +

7

13

5

4

25

Capromys pilorides

7

16

7

4

17 +

Aulacodus swindernianus

7
7

13

15

6
6

4
4

6 +

insidiosus
Hystrix cristata

7
7

17
iq

5
4

3
4

36

12

hirsutirostris

7

ic

4

4

II

javanica

7

14

5

4

10 +

7

6

21 +

Lagostomus trichodactylus ...

7
7

7
7

3
4

20
10 +

Coelogenys paca

7

6

5

7 +

Cavia porccllus

7

6

4

7

Dolichotis patachonica

7

12

8

9 +

Hydrochoerus capybara
Lepus timidus

7
7
7
7

H
H
13
12

5
6
6

7

4

•5
O

3

4

6
13

variabilis ...

7

12

7

4

'3

cuniculus

7

12

7

4

15

INSECTIVORA.
Chrysochloris aurea

7

IQ

5

j
8

Centetes ecaudatus

7

10

c

8

* ,,

7

10

4

8 +

Hemicentetes semispinosus...
Ericulus setosus

7
7

16
17

5
6

3
4

9
9

Microgale longicaudata
Solenodon cubanus

7
7

14
I c

7

4.

2

e

43

2}

Talpa europira

7

I ^

6

c

II

Myogale mo.schata . .

7

I ^

6

c

27

pyrenaica . . .

7

I 3

6

c

3O

Crocidura cterulescens . .

7

Id

6

4

17 +

Sorex vulsjaris .

7

6

4

1C

Erinaceus europasus

7

14.

6

4

I [

7

I c

I I

7

16

0 +

Gymnura raffles!

7

1C

C

28

Galeopithecus volans

7

13

6

c

I4.+

VI.]

IN VARIOUS MAMMALS.

Insectivora.

Cervic.

Thorac I.umb.

Sacral.

Caudal.

Galeopithecus volans

7

7
7

7
7
7
7
7
7
7
7
7
7

7
7
7
7

9
9
9

7
7
7
7
6
6
7

7
7
7
7
7
7

'3
14
'4

'3

12
14
>4
II
II
12
12
II
II
12

II
12

'3
II

16
'5
'4
24
24
23
23

22
23

16

15
15

16

17
17
IS

8
6

5
5
5
4
7
7
6

4

5
5
4

5

6
6

3
4
4
3
3
3
4
3
3
3

^^^•v

1C

3

2
2

3

2

5
4
4

coal

1
1
1
1
3
3
3
3

l
l

4
coalc

6
6
5

7
6
8
5
7
8

5

~^—

>

5
3
5

6

'5
17

17 +

ssced.

2

6
8

2
O
II
II
II

3
5
ii

•seed.

ii

8
n
6

4
4

5
4
17

21

29
2.3 +

37

24 +

35

• )t

pbilippinensis..

CHIROPTERA.

Epomophorus franqueti
Pteropus ruhricollis

medius

Cynopterus marginatus
Phyllorhina tridens

diaclema . ...

caflfra

Megadcnna frons

Vesperugo scrotinus

noctula .. ,

pipistrellus
nanus

Miniopterus schreibersi
Molossus obscurus

Desmodus rufus

EDENTATA.
Bradypus tridactylus

Cholcvpus didactylus

* >»

hoffmanni

Megatherium americanum ..
Mylodon robustus

Myrmecophaga jubata . ...

* »»

Tamandua tetradactyla
»>
»i

NUMBER OF VERTEBRA.

[CHAP.

Edentata.

Cervic. \ Thorac. ' Lumb.

Sacral.

Cycloturus didactylus

7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7

7 •

7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7

16

10

ii
9
9
ii
ii
ii

12
12
II
II

14

16
17
15
15
14
14
13
13

left side
12

rightside

'5

15
13
II
II
II
13
13
13
13
13
13
13
13
13
13
13

2
5

5
5
4
3
3
3
3

2

3
3

5
5
5
6
6

5
6
8

I')
M

4
6
8

7
6
6
6
6
6
6
6
6
6
6
6

4
9
9

8
8

9
8
8

10

13

13

10

5
4
4
4
3
4
3
6

6

4

5
4
3

4

j

2
2

3
3

2

2

2
2

2

2

Tatusia novemcincta

hybrida

Dasypus sexcinctus .

villosus .

minutus

Xenurus unicinctus

Priodon giganteus

Tolypeutes conurus

Chlamydophorus truncatus ...
Manis pentadactyla

aurita . .

javanica

gigantea

macrura

Orycteropus capensis

MARSUPIALIA.
Phascolomys wombat

platyrhinus
latifrons

Phascolarctos cinereus

Phalangista vulpina

cooki

Petaurus australis

sciureus

Macropus giganteus

antilopinus

bennetti

Dendrolagus ursinus

Hypsiprymnus murinus
Bettongia gaimardi . .

Caudal.

40
16 +

22
16 +
2O

16
19

12 +

12 +

23
II

15

28
26

13 +
28
30
28

49
26

27

13
15

8 +

7

7

8
27
25
25
17 +
15 +
23
23
24
10 +

23
23

VI.]

IN VARIOUS MAMMALS.

Marsupial ia.

Cervic Thorac. Lumb.

I

Pcrameles ol>esula 7 13 6

Myrtnecohius fasciatus 7 12 7

Phascogale flavij>es 7 '3 ^

Dasyurus maculatus 7 13 6

viverrinus 7 13 6

ursinus 7 13 6

Thylacinus c>nocephalus 7 13 6

Didelphys virginiana 7 13 6

a?ane 7 . 13 6

Chironcctcs varicgatu-s 7 13 6

MONOTREMATA.

Kchidna aculcata 7 16

» liruijni 7 16 4

Ornithorhynchus anatinus ... 7 17 2

Sacral.

Caudal

15
24
10 +

19 +
13 +
16 +

23
26
29
29

II

10
20

CHAPTER VII.

THE STERNUM.

THE Sternum of Mammals is a bone, or generally a series
of bones, placed longitudinally in the middle line, on the
inferior or ventral aspect of the thorax, and connected on
each side with the vertebral column by a series of more or
less ossified bars called ribs.1

It is present in all Mammals, but varies much in character
in the different groups.

When in its usual and most complete form (see Fig. 31),
it may be divided into three parts, called respectively —

1. Presternum, or " manubrium sterni " of human ana-
tomy.

2. Mesosternum, body of the sternum or gladiolus.

3. Xiphisternum^ xiphoid or ensiform process of the ster-
num.

The mesosternum is usually composed of several distinct
segments, which may become ankylosed together, but more
often permanently retain their individuality, being con
nected either by fibrous tissue or by synovial joints.

1 For much valuable information upon the structure and development
of the sternum, see W. K. Parker's " Monograph on the Shoulder-girdle
and Sternum of the Vertebrata," published by the Ray Society, 1868.

CHAP. VII.]

GENERAL CHARACTERS.

9»

The ribs are attached to the sides of the sternum : the
first pair to the presternum ; the second to the presternum
and the mesosternum at their point of junction ; the
remainder to the mesosternum, opposite the interspaces
between each segment, though two or more pairs are often
clustered round the last segment. The xiphisternum bears
no ribs.

Development. — The osseous sternum is preceded by a
continuous or non-segmented piece of cartilage ; and as the

m*

FIG. 31 — Human sternum and sternal ribs, J. /i presternum ; mt mesosternum ;
jet xiphisternum ; c point of attachment of clavicle ; i to to the cartilaginous
-ternal rids.

portion of the body in which this is developed is formed by
the union in the middle line of the two " ventral laminae " of
the embyro, traces of this original median division are generally
seen in very young sterna, and are often persistent through

92 THE STERNUM. [CHAP.

life in the form of fissures or fenestrse in the middle line
of the sternum. Each segment ossifies from a single nucleus,
or from two nuclei placed one on each side of the middle
line, and which usually become blended together in the
course of growth. Sometimes epiphyses are added to the
ends of the segments. The terminal portion of the
xiphisternum generally remains cartilaginous through life.

Special Characters of the Sternum in the various Orders.

Order PRIMATES. — In Man (see Fig. 31,) the presternum is
broad and flat, hollowed in the middle line in front, and
expanded laterally to give large surfaces for the attachment
of the clavicles and the first pair of ribs. The mesosternum
is elongated, but is also comparatively broad and flattened.
It consists of four distinct segments. The xiphisternum is a
more or less elongated posterior appendage, varying some-
what in form and size in different individuals.

The ossification of the human sternum is endosteal, or
commencing within the substance of the primitive hyaline
cartilage. The presternum ossifies from one, or sometimes
two, centres, which may be placed side by side, or one in
front of the other. Each of the segments of the mesosternum
has a distinct centre, though these may be double in their
earliest condition, and sometimes remain so for a long
period.

The segments of the mesosternum usually unite together
so as to form one continuous bony piece, to which the pre-
sternum often remains throughout life connected only by
fibrous tissue, although it is not unfrequently ankylosed in
old age.

The xiphisternum ossifies irregularly and imperfectly.

The Gorilla, Chimpanzee, Orang, and Gibbons, resemble
Man, and differ from the other monkeys in the breadth

VII.]

PRIMA T£S.

93

and flatness of the sternum. It is broadest in proportion
to its length in the Siamang (Hylobates syndactylus). In
the Orang (Fig 32), each segment of the mesosternum
is developed from a pair of lateral ossifications, which
commonly remain separate until the animal is about half
grown.1

In the lower Monkeys, the presternum is somewhat broad
but the bones constituting the mesosternum are elongated
and compressed, and are not ankylosed together as in Man
and the highest Apes. Their number varies from three to
five. In the Howling Monkey
(Mycetcs) the original two halves of
the presternum are separated by a
broad fissure, and form a pair of
diverging, horn-like, bifurcated pro-
cessess (pro-ostta, Parker), which
ossify separately, and support the
clavicles and first pair of ribs. Ac-
cording to Albrecht - this condition
of the manubrium is in relation
with the enormously developed thy-
roid cartilage in the male Mycttes, and
is therefore a secondarily acquired
condition.

In the CARNIVORA, the sternum
(Fig. 33) is generally composed of eight or nine pieces
altogether, including the presternum and the xiphisternum.

The presternum, or manubrium, is long and narrow,
somewhat expanded near the front for the attachment of the

1 The sternum of a young Gorilla in the Museum of the College of
Surgeons presents the same condition.

- Su> la Elbnens Alorpholo&iquts du Manubrium Sterni. (Brussels,
1884.)

JCt

FIG. 33. — Sternum of young
Orang (Sitnia latyrtts). fs
presternum ; mt meso*ter-
nuiii ; jcs xiphisternum.

94

THE STERNUM.

[CHAP.

Parker, ectosteally.

first pair of sternal ribs, and terminating anteriorly in a
conical rounded projection.

The segments of the mesosternum are elongated, and
more or less four-sided, contracted at the middle, and
widening at each extremity. They ossify, according to
or from without inwards, the bony
deposit commencing in the inner layer
of the perichondrium, as in the shafts
of long bones ; and they remain per-
manently distinct from each other.

The xiphisternum is long, narrow,
and flat, and generally ends in an ex-
panded flattened cartilage.

In the Pinnipedia, the presternum
is produced considerably in front of
the attachment of the first pair of
ribs.

In the INSECTIVORA, the sternum
is variable in form, but always more
or less elongated and segmented.
The presternum is always more or
less expanded laterally in this clavi-
culated group of aninials. It is bilo-
FIG. 33.— sternum and sternal bate in front in the Hedgehog

ribs of Dog (Ca.nisfa.tni- , „ . \ ^ -i i ., • ^i 01

Han's), if. /.? presternum ; (fcrinaceits), trilobate in the bhrews

jus mesosternum ; .rs xiphi- /r, \ T /-> , , v • i j

sternum. (Sorex). In Rliynchocyon it is broad

in front, narrow posteriorly, strongly

keeled below, and with two horn-like processes projecting
outwards and forwards between the attachment of the
clavicles and the first pair of ribs.

The mesosternum is usually narrow, as in the Carnivora,
but in the Hedgehog, where it consists of three segments,
it is broad and flat posteriorly, and to the last segment three

VII.]

INSECT1VORA.

95

ribs are attached. In this genus the xiphisternum is rudi-
mentary, whereas in the Shrews it is long and ends in a flat
expanded cartilage.

The Mole (Talpd) and its nearest allies have a remark-
ably developed presternum, which is as long as the whole
of the mesosternum (Fig. 34). It is strongly keeled below,
except at the front part, which is much thickened. On its

'/

KIG. 34.— Sternum and siernal rib< of the Common Mole (Talfa eurofaa)v\lh the
clavicles (cl) and humeri (//). Nat. size.

superior or inner surface it is grooved in the middle line.
Laterally it gives off a pair of wing-like processes, behind
which the first ribs are attached. It is distinctly separated
from the mesosternum, which consists of five segments of
nearly equal width. The xiphisternum has a broad oval
cartilaginous expansion posteriorly.

96 THE STERNUM. [CHAI>.

As the clavicle is supported at the anterior extremity of
the elongated presternum, it is widely separated from the
first rib, and the anterior extremities are brought into such
close juxtaposition with the head that the animal appears to
have no neck.

In the CHIROPTERA, the sternum presents a considerable
general resemblance to that of Man. The presternum is
large, trilobate in front, and strongly keeled. The meso-
sternum is likewise frequently strongly keeled (Pferop2ts,
Cynonycteris), but this keel is separated from that of the
presternum by a deep notch. In many of the Insectivorous
Bats the segments of the mesosternum are (at least in adults)
firmly ankylosed together, but in some of the frugivorous
Bats (Pteropus, &c.) they continue separate.

In the RODKNTIA, the sternum is long and narrow, consist-
ing of a presternum (which is generally broad in the forms
which have the clavicle well developed, as the Rats, Beavers,
&c.), a mesosternum of three, or more usually four, seg-
ments, and a long xiphisternum, with a broad cartilaginous
terminal expansion. The segments of the mesosternum
often have epiphyses at each end.

The presternum is compressed and produced forwards in
those species in which the clavicle is absent or rudimentary,
as the Aguti, the Hares, and the Capybara. In the latter it
much resembles that of the Horse or Tapir.

Order UNGULATA. — In the Ruminantia there are usually
seven segments altogether in the sternum (Fig. 35). The
presternum is narrow, rounded in front, and bearing the first
pair of sternal ribs close to its apex. The succeeding pieces
gradually widen, the posterior segments of the mesosternum
being square, flat, and rather massive (especially in the
Giraffe) ; they are hollowed at the middle of their lateral
borders. The xiphisternum is thin and flat.

VII.]

UNGULATA.

97

In the Pig (Fig. 36) and Hippopotamus the presternum is
( ompressed and keeled ; the articular facets for the first
pair of ribs are close together on its upper surface ; but the
mesosternum is broad and flat, the first segment being
transitional, compressed in front, and broad posteriorly.

FIG. 35. — Sternum and sternal ribs of
Red Deer (Cftvn t elaf-hut), \. fs

the

presternum ; mi

xiphisternum.

nicso-icrnum

KH;. 36 —Sternum of the Pig (S*i
scro/a), \. fit presternum ; tin meso-
sternum ; .rt xii>histcmum.

The xiphisternum is narrow and pointed. The sternum of
the Pig very often retains indications of the primordial
median fissure through life.

The Horse and the Tapir have a very peculiar sternum.

H

98 THE STERNUM. [CHAP.

The presternum is extremely compressed and projects
forward like the prow of a boat. In the Tapir, its anterior
portion is originally, and commonly remains, a distinct
ossification (pro-ostcon, Parker). The segments which
follow gradually widen, and the hinder part of the sternum
is broad and flat. The last mesosternal segment in the
Tapir is generally divided in the middle line.

The sternum of the Rhinoceros is very narrow through-
out, with a long, rather spatulate xiphisternum.

Order CKTACF.A. — Each of the two primary divisions of
this order has a distinct form of sternum.

Among the Odontcceii, the typical Dolphins have a very-
broad presternum of peculiar form, emarginate in the middle
line in front, and with a pair of lateral processes behind the
attachment of the first pair of ribs. This is followed by two
or three mesosternal segments but no xiphisternum. An
indication of the primordial median fissure can generally be
traced, except in very old animals, either as a hole in the
presternum, or as a division of the posterior mesosternal
segment.

In the Porpoise (P/iocfcna) the sternum is shorter and
broader than in most Dolphins, and its various elements
early coalesce into a single bone.

In the Cachalot (Physeter macrocephalus) the sternum
ossifies from three distinct pairs of nuclei, and a large
median fontanelle remains between the first and second
pair.1 In the specimen in the Museum of the Royal College
of Surgeons (Fig. 37), which is very nearly adult, each half
of the presternum (ps) has coalesced with the corresponding
half of the first segment of the mesosternum (;//-$•'), but the
resulting pieces are not united by bone across the middle
line, while the second or last pair of mesosternal segments
1 I have observed this in animals evidently of great age.

VII.]

CETACEA.

99

(ms-) are ankylosed together mesially, but not with the
portion of the sternum in front of them.

FIG. 37. — Sternum of Cachalot or Sperm Whale (fkyseter tnacrorefkalux), fa.

In the Whalebone Whales (Afystacoceti} the sternum is
comparatively rudimentary, consisting only of a broad,

FlC. 38. — Sternum of Greenland Right Whale (Baftma myslicetut), /,.

flattened presternum, produced posteriorly into a xiphoid
process in some species. There are never any mesosternal

H 2

THE STERNUM.

[CHAP.

segments, and consequently no ribs, other than the first
pair, are attached to it.

The presternum is ossified from one, or perhaps a pair of
symmetrical nuclei. In the Right Whales (Balana, Fig. 38)
it is heart-shaped, or longitudinally oval; in the Fin Whales
(Batenoptera, Figs. 39, 40, and 41) it is transversely oval
or trilobate, with a backward projecting xiphoid process.1
In young animals ossification of the cartilaginous sternum
advances forwards on each side of the middle line, so that

FIG. 39. — Sternum of Common Rorqual or Fin FIG. 40. — Sternum of Pike Win
Whale (Bal&noptera musculus), ,V (Balifiwptera rostrata), ,*,.

the ossified portion at one period appears deeply notched in
front ; as the bone meets across the middle line anteriorly,
this notch usually becomes converted into a hole (see
Fig. 39), which finally closes with complete maturity.

1 In the cartilaginous sternum of a young F!al<cnoptcra sibbaLiii
Professor Turner found the xiphisternum to be quite distinct from the
presternum, and connected with it by fibrous tissue. (Journal of
Anatomy, May 1870.) In most Whales the sternum shows no such
evidence of segmentation.

VII.]

SIRENIA.

101

In the Lesser Fin Whale (/?. rostratd) the sternum is
cross-shaped (Fig. 40), the first ribs being attached behind
the Literal arms of the cross.

FlG. 41 — Sternum of Rudolphi's Whale (RaJtrnafltra A.'rra/is). showing its relation
l'i the inferior extremities uf the first pair of ribs. From " Proceedings Zoological
Society. 1883."

In the SIKKNIA the sternum is a simple, flattened, some-
what elongated bone, which in the adult shows no trace of
segmentation.

FIG. 42. — Sternum of a young Dugong (Halicore indicia), \. From a specimen in
the Leydcn Museum.

In a young Dugong (Ilalicore), Fig. 42, there are two
distinct ossifications, — a presternum (/j), to which the first

io2 THE STERNUM. [CHAP.

pair of ribs are attached, and a xiphisternum (xs). The
second, third, and fourth pairs of sternal ribs are attached
to the intermediate unossified portion, representing a rudi-
mentary mesosternum.

In the Manatee (Manatus) the sternum is of somewhat
similar form, and has three pairs of ribs attached to its
lateral margins near the middle.

Among the EDENTATA there is considerable variation in
the characters of the sternum.

In the Cape Anteater (Orycteropus) the sternum is of
quite a normal form. The presternum is trefoil-shaped,
expanding laterally near the front to meet the largely
developed clavicles, then contracting to the width of the
mesosternal segments, which are four in number, simple,
flattened, oblong, with lateral margins nearly parallel,
rather broader above than below, united together by fibrous
tissue, and succeeded posteriorly by a moderately developed
xiphisternum.

In Manis aurita the sternum is flat, consisting of seven
segments, several of which are sometimes divided in the
middle line by synovial cavities. The xiphisternum is
very long, partially cleft in the middle line, and ending in
a large flattened cartilaginous expansion. In the Long-
tailed Pangolin (Manis macrura] the xiphisternum is of a
remarkable form, being prolonged into a pair of cartila-
ginous processes, each about nine inches long, and con-
nected posteriorly with some rudimentary abdominal ribs. '

In the Anteaters (Myrmecophaga) the presternum is broad,
flat, and oval. The segments of the mesosternum (Fig. 43)
are eight in number, short, deep, broad above, and sending
a club-shaped process downwards ; each is ossified from a
principal endosteal centre and eight epiphyses, is connected

1 Parker, op. fit. p. 208.

vii.] EDENTATA. 103

by synovial articulations with the segment before and behind,
and has at either end an upper and lower hollowed surface,
which, with the corresponding surfaces on the contiguous
segment, form articulating facets for the double-headed
sternal ribs. This mode of articulation curiously resembles
that at the vertebral end of the rib. The xiphisternum is
rather long and simple.

In the small Tree Anteater (Cycloturus didactylus) the
presternum is very broad and trilobate, sending out lateral
expansions behind the attachment of the clavicles to meet

mtt

FIG. 43 —Side view of three mesosternal segment* of a young Anteater (Myrnte-
cofHaga t<iman<iua\ showing the mode of articulation of the sternal rib (jr).
copied from Parker's figure, nisi thi upper or inner surface of the mesostcrnal
segment ; ty the synovial articulation between the segments.

the first pair of ribs. The hinder, narrow part of the manu-
brium is segmented off from the larger anterior part, and
resembles a mesosternal segment ; but it is in front of the
attachment of the second pair of ribs. The true mesosternal
segments are six in number, of nearly equal width, high,
rounded above, and con-. pressed below, with a synovial
cavity between each. The sternal ribs are articulated by a
single oval condyle. The xiphisternum is long, stout, and
styliform.

104 THE STERNUM. [CHAP.

In the Armadillos (Dasypodidce) the presternum is broad,
and in Priodon gigas (Fig. 45, p. 114) strongly keeled. The
mesosternal segments, four to six in number, are broad above,
but very narrow below. They are connected by synovial
joints to each other, and to the strongly ossified sternal ribs,
which have broad, sub-bifid heads. The xiphisternum
expands posteriorly into a wide cartilaginous flap.

In the Sloths the sternum is long and narrow. The Three-
toed species {Bradypus} have a rather broad presternum, but
with no prolongation in front of the attachment of the first
rib. This is followed by eight small mesosternal segments,
and a very small rounded xiphisternum. In the Two-toed
Sloths (Cholazpus) the presternum is narrow, slightly keeled,
and forms a considerable projection in front of the attach-
ment of the first rib. The mesosternum has twelve segments,
and the xiphisternum is rudimentary or absent.

In the MARSUPIALIA the sternum presents no especial
aberrant characteristics. The presternum is rather broad at
the point of attachment of the first pair of ribs. Its anterior
extremity often does not ossify. There are usually four
quite distinct, elongated segments to the mesosternum, con-
nected to one another by fibrous tissue, and sometimes
completed at each end by epiphyses. The xiphisternum
has an elongated, narrow, ossified portion, and terminates
in a laterally expanded cartilage, which may contain one
or two endosteal bony patches.

In the MONOTREMATA the Ornithorhynchus (Fig. 44) has
a broad presternum (ps\ with a small partially-ossified
pro-osteon (po) in front of it ; three keeled mesosternal
segments (;;«), which commence to ossify in pairs, and
no xiphisternum. The Echidna agrees in all important
respects, but it has an ossified xiphisternum, which in E.
Bruijni consists of three metameric portions.

VII.]

MONOTREMATA.

The T-shaped bone, interclavicle or episternum. (if) in front
of the presternum, which connects it with the clavicle
and is often completely fused with it, appears to have

FIG. 44. — Sternum and adjacent parts of the skeleton of a young Ornithorhynchus
(l). anatini4i) ( clavicle ; if interclavicle ; fx> pro osteon (a part of the true
kternum) ; fs prcstcrnum ; nis mcsostcrnum ; sr sternal ribs ; ir intermediate ribs ;
vr vertebral nbs.

no homologue among the other Mammalia, and belongs
more properly to the shoulder-girdle than to the sternal
apparatus.

CHAPTER VIII.

THE RIBS.

THE ribs form a series of long, narrow, and more or less
flattened bones, extending laterally from the sides of the
vertebral column, curving downwards towards the median
line of the body below, and mostly joining the sides of
the sternum.

Free ribs are normally only attached to the thoracic ver-
tebras, although, as before shown, certain parts, which may
be serially homologous with ribs, are found in other regions
of the vertebral column ; but in such cases they become,
almost always, ankylosed with their corresponding vertebras.
In the thoracic region, the ribs are never normally ankylosed
with the vertebrae, but are articulated to them by synovial
joints, which permit a certain, though limited, amount of
motion.

As a general rule, the first thoracic rib joins the pre-
sternum or manubrium ; sometimes, as in the Whalebone
Whales, this is the only rib united to the sternum ; but
usually a larger number are so connected, while the more
posterior are either attached by their extremities to the
edges of the ribs in front of them, and thus indirectly join
the sternum, or else they are quite free below, meeting no

CHAP, viii.] GENERAL CHARACTERS 107

part of the skeleton. These differences have given rise to
the division into true ribs and false ribs (by no means good
expressions), signifying those that join the sternum directly
and those that do not ; and of the latter, those that are
free below are called floating ribs.

Each primary piece of cartilage, out of which one of the
half hoops or ribs is developed, is, moreover, divided trans-
versely into two portions, which assume different characters,
as they usually undergo a different mode of ossification, and
remain more or less distinguishable from each other during
life. The portion nearest the vertebral column is called
the vertebral rib. This is the larger segment, and becomes
firmly ossified at an early period by ectostosis ;l it is the
bone commonly spoken of as a "rib."

The portion towards the sternal extremity or sternal rib
is usually imperfectly ossified, and always at first (except
in Monotremes) by cndostosis? Sometimes it remains per-
manently in a cartilaginous state ; but, on the other hand, in
some cases (as in Armadillos and Sloths) it becomes as firmly
ossified as the vertebral ribs.

The vertebral ribs are variously connected with the sternal :
by continuous cartilage, by intercalation of fibrous tracts,
or by synovial joints.

Occasionally, in the Mammalia, an " intermediate "
portion of the rib is segmented off, as in Reptiles ; this is
best developed in the Monotremata (Fig. 44, />), where,
however, it is only partially ossified by cndostosis. In all
other instances in which it occurs (e.g., Odontoccti} it is
quite rudimentary.

1 The bony deposit commencing at the surface, and advancing in-
wards, as in ordinary long bones.

'J The bony deposit being irregularly scattered throughout the carti-
lage, often beginning near its central part.

io8 THE RIBS. [CHAP.

The vertebral ribs, when in their most typical condition,
have two points of attachment to the vertebrae : the tubercle
(tubcrcului)i) and the head (capituluiri). The former is
superior or dorsal and posterior, and attached to the trans-
verse process of the vertebra ; the latter, inferior or ventral
and anterior, and attached to the body of the vertebra, or
the inferior part of the arch near the body, and always very
near the neurocentral suture. Commonly, in fact, the
articular surface is cut by this suture. Sometimes, as in Man,
the greater part of the articulation is above the suture;
or, on the other hand, it may be, as in the Monotremes,
below the suture. The distinction between the two points
of attachment is most marked in the anterior ribs ; in
passing backwards they approach nearer to each other,
sometimes becoming blended, or sometimes either one or
the other (generally the tubercular) attachment is lost in the
hindermost ribs.

The tubercle articulates, by a nearly flat or slightly con-
vex surface, to a facet on the under-surface of the extremity
of the transverse process of the corresponding vertebra, but
the more rounded capitulum (at least in the anterior ribs) is
placed opposite to the intervertebral space in front of this
vertebra, and portions of two vertebra commonly contribute
to form the articular cavity for its reception. Thus the first
rib is articulated by its tubercle to the transverse process of
the first thoracic vertebra, and by its head to the hinder
part of the seventh cervical and front part of the first
thoracic vertebra, and so on. The posterior ribs, as a rule,
are connected solely with their own corresponding vertebra

The amount of motion permitted by these articulations
is sufficient to allow the thorax to expand and contract in
respiration. In inspiration the ribs are drawn forwards, and
approach nearer to a right angle with the vertebral column,

viii.] GENERAL CHARACTERS. 109

while in expiration they fall back, and occupy a more
oblique position to the axis of the column.

The sternal ribs are connected with the sternum either by
interposed fibrous tissue or by distinct synovial joints. The
first is attached to the side of the presternum, the second
opposite to the junction of the presternum and the first
mesosternal segment, and the succeeding ones opposite to
the interspaces between the other mesosternal segments ;
though two or more may be attached to the hinder end of
the last of these segments. The inferior ends of the so-
called " false ribs " are attached by fibrous tissue, or by
synovial joints, to the hinder borders of the sternal ribs in
front ; though, as before said, the most posterior are free or
" floating."

The ribs of existing Mammals never have "uncinate
processes," like those found in Birds and Reptiles.

The most prevalent number is thirteen pairs ; the lowest
is nine (in Hyptroodoii), the highest twenty-four (in the Two-
toed Sloth, Cholocpus).

Special Characters of the Ribs in the various Groups rf
Mammalia.

Order PRIMATES. — In man there are normally twelve
pairs of ribs, of which the first seven are reckoned as true
ribs and the last two as floating ribs. The last pair may
be rudimentary or absent ; or, on the other hand, the seventh
cervical or the first lumbar vertebra may have an additional
movable rib articulated with it.

The first vertebral rib is much shorter, broader, flatter,
and more curved than the others. These gradually increase
in length until the seventh, after which they again diminish
to the twelfth. In breadth they gradually decrease from the
first to the last.

no THE RIBS. [CHAP.

The portion of the rib between the head and the tubercle
is called the neck ; it is wanting in the last two ribs, in which
the two attachments are blended. The greatest point of curva-
ture on the external surface of the rib is called the angle.

Each vertebral rib has a main centre of ossification and
two epiphyses, one for the head and (except in the last
two) one for the tubercle.

The sternal ribs generally remain cartilaginous throughout
life, being only partially ossified by endostosis in old age or
under abnormal conditions. They are not distinctly sepa-
rated from the vertebral ribs except by their difference of
structure ; but synovial joints are (except in the first) inter-
posed between their inferior extremities and the sternum.

Among the higher Simiina the ribs do not differ very
notably from those of Man, except in number; but in the
lower forms, and especially in the Lemitrina, they more
resemble those of the Carnivora. Among the Old World
Monkeys the number varies from n to 13 pairs. The
Gorilla, Chimpanzee (Troglodytes} and Gibbon (Ifylobates)
have 13, and the Orang (Simia] 12. In the American
Monkeys there are from 12 to 15 pairs; in the Lemurs
from 12 to 17 pairs.

In the most typical forms of CARNIVORA the vertebral
ribs are comparatively slender, subcylindrical, and little
curved. The most anterior espjcially are short and straight,
the thorax being thus more compressed in front than it is in
Man and the higher Primates. The sternal ribs (see Fig.
33, p. 94) are long, slender, have a feeble granular ossifica-
tion, and are not otherwise segmented off from the vertebral
ribs. In all the Fdidcc and Canidce- there are 13 pairs, in
the Viverridcc 13 or 14, in the Hyienidtc 14 or 15, in the
Mustdidic 14 to 1 6, in the Procyonid<z 14, in the Ursidtc 14
or 15, in the Pinnipcdia 14 or 15,

vni.] UNGULATA-CETACEA. in

In the UNGULATA the ribs are generally more or less
flattened and broad, notably so in the Ox and Camel, and
least so in the Perissodactyla. The anterior ribs have
scarcely any curve, the thorax being very narrow in this
region. The sternal ribs (see Fig. 35, p. 97), especially
those near the front of the series, are short, stout, rather
flattened or prismatic, tolerably well ossified, and articulated
with the vertebral ribs by a cup and-ball synovial joint.
The Artiodactyles have from 12 to 15 pairs of ribs, the
Horse and Tapir 18, the Rhinoceros 19, the Elephant 19
or 20, and the Hyrax 20 to 22.

In the SIRKNIA the total number of ribs is very great,
though but tew are attached to the sternum. In the Manatee
they acquire an extraordinary thickness and SDlidity of
texture. This animal has 17 pairs, of which but three are
attached by flexible cartilages to the sternum.

Order CETACEA. — In the Whalebone Whales the ribs differ
greatly from those of the rest of the Mammalia in their ex-
tremely loose connection, both with the vertebral column
above and with the sternum below, probably to allow of greater
alteration in the capacity of the thorax in respiration neces-
sitated by the prolonged immersion beneath the surface of
the water which these animals undergo.

At their vertebral extremities they are attached only by
their tubercle to near the end of the transverse process, but
apparently not by synovial articulation. The heads of only
a few of the anterior ribs are developed, and are rarely
sufficiently long to reach the bodies of the vertebrae, their
place being supplied by a ligamentous band. The first rib
is the only one connected with the sternum, either directly
or indirectly, the whole of the remainder being free or
floating ribs. The sternal ribs are mere cartilaginous rudi-
ments, connected by an intermediate layer of fibrous tissue

U2 THE RIBS. [CHAP.

to the inferior extremity of the vertebral rib ; at least such
is their condition in the foetus of Balcena mysticetus, as
described by Eschricht and Reinhardt.

Balanoptera rostrata, the smallest of the Whalebone
Whales, has but n pairs of ribs, Megaptera longimana 14
pairs, the Greenland Right Whale (Balcena mysticetus)
usually 13, and the larger Fin Whales (Balcenoptera musculns
and sibbaldt) 15, and occasionally 16, the highest number
known in any Cetacean. In these last it not unfrequently
happens that the hindermost rib, having only the middle or
lower portion developed, is separated by a wide interval
from the vertebral column — a very rare condition, as in most
other cases where the hinder ribs are rudimentary the part
in immediate connection with the vertebra remains.

The first rib presents a very anomalous condition in some
Whalebone Whales, being apparently double, probably owing
to the coalescence of a supplemental cervical rib with the
ordinary first thoracic rib. In some species (as Bahcnoptera
borealis] this appears to be of almost constant occurrence ; in
others it is occasional.1

In the Odontoceti or Toothed-whales, as the Common Dol
phiri and Porpoise, the ribs (usually 12 or 13 pairs) are long
and slender. The first four or five have tubercles, by which
they articulate with the transverse process of the thoracic
vertebrae, and long necks and heads, reaching to the side of
the antecedent vertebra, rear the junction of the body and
the arch (see Fig. 20, p. 59). The posterior ribs, however,
lose the neck, and are solely articulated by the tubercle to
the transverse process. There are usually 7 pairs of rather
short, straight, but strongly ossified sternal ribs nnd often
small intermediate ribs, sometimes distinctly ossified.

1 See Professor Turner " On the so-called Two-headed Ribs in Whales
and in Man." (Journal of Anatomy and Physiology, May 1871.)

v in. ] CE TA CEA. —EDENTA TA. 1 1 ;

In the aberrant Physfteiidtey including tlie Sperm Whale,
Hyperoodon, and various forms of Ziphioids, the ribs are
connected to the vertebrae throughout the greater part of the
series by both head and tubercle; but a few of the most
posterior have only a single point of attachment, in con-
sequence of the changes which take place in the condition
ot the transverse processes of the vertebra.', described at
p. 59. In this family the sternal ribs are either j>ermanently
cartilaginous, or very imperfectly ossified. The Hyperoodon
has but 9 pairs of vertebral ribs, the smallest number
known in any Mammal; the Sperm Whale (Physder) u,
of which the last is quite rudimentary; Ziphins, 10, and
A'o;/V7, 14.

Among the EDENTATA the Sloths have very numerous
ribs (from 15 to 24 pairs, the latter number in Choltcfnis
didactvhis, of which 12 are true ribs). In the anterior part of
the thorax the sternal ribs are firmly ossified, and indistin-
guishable from the vertebral ribs (at least in adult age),
but posteriorly they are separated from the latter by a less
perfectly ossified intermediate rib.

In the Armadillos (Fig. 45) the ribs are comparatively few
(10 to 12 pairs), and are broad and flat, the first extremely so.
The first sternal rib is very short and incorporated with the
vertebral rib, but the others are very strongly ossified, and
articulated by synovial joints with the sternum, with each
other, and with the vertebral ribs.

The peculiar double articulation of the sternal ribs with
the sternum in the Anteater (Afyrmteophaga) has been already
described (see p. 102). The ribs of the small climbing Two-
toed Anteater (Cydoturus dideutylus) are remarkable for a
thin lamelliform expansion of their hinder border, over-
lapping the succeeding rib. This animal has 15 pairs, the

THE RIBS.

[CHAP.

great Anteater 16, the Cape Anteater (Orycteropus) 13, of
which the last is sometimes very short.

The MARSUPIALIA have nearly always 13 pairs of ribs :
the Koala (Phascolarctos) with but n, and the common
Wombat (Phascolomys vombatus] with 15, being the only
known exceptions. The sternal ribs are articulated by
synovial joints with the sternum, but are not distinctly
segmented from the vertebral ribs, and are but feebly
ossified bv endostosis. There are no intermediate ribs.

Fir,. 45. — Sternum nnd ribs nf the Great Armadillo (Priodon f>igas), \.
ps presternum ; xs xiphisternum.

In the MONOTREMATA the intermediate ribs are well
marked (see Fig. 44, p. 105), and only partly ossified by
endostosis, while the sternal ribs (except the first) are,
according to Parker, strongly ossified ectosteally, as in Birds.

viii.] MONOTREMATA. 115

The hinder sternal ribs are very broad and flat. The
Echidna has 16, and the Ornithorhynchus 17 pairs of
vertebral ribs ; they do not divide above into head and
tubercle, but are attached only to the sides of the bodies
of the vertebra;. The last 5 sternal ribs of Echidna, especi-
ally E. bruijni, are exceedingly broad and overlap each
other.

I 2

CHAPTER IX.

THK SKULL.

THE skull is the term commonly applied to the expanded
anterior portion of the axial skeleton situated within the
head.

It consists mainly of the cranium, a strong bony case or
frame, enclosing the brain, and affording support and pro-
tection to the organs of smell, sight, hearing, and taste, and
formed by the close union, either by sutures or by synostosis<
of numerous bones.

To the inferior surface of the cranium are suspended (i)
the Mandible, or lower jaw, movably articulated by a syno-
vial joint; and (2) a group of skeletal structures called the
hyoidean apparatus.

The diagram at p. 126 is intended to show at a single view
the names applied to the various bones of which the skull is
composed, and to give some idea of their relative position.

It will be well to commence the study of the skull by
describing that of a Dog, as a good average specimen of the
class, and one which is easily procurable at various ages :
and the student is strongly advised to follow the descrip-
tion with a skull in his hand, or better still, two, in one of
which a longitudinal median section has been made. In
the other, the various bones should be separated from each

CHAP. IX ]

THE SKULL OF THE DOG.

"7

other. For this purpose a young animal, still retaining the
milk teeth, will be best.1

The skull has a longitudinal central axis (the cranio-facial
axis, Huxley), around which all its parts are arranged, and

U

id

Km. 46 — longitudinal and vertical section of the skull of a Do({ (Canit/amiliarii),
with mandible ami hyoid arch, J. an anterior narial aperture; MT maxillo-
turliiii.il bone; KT ethmo-turbinal ; A'<* nasal; ME ossified portion of the
mesethmoid ; CK cribriform plate of the clhmo-turbinal ; /> frontal; Pa parietal ;
//' interparietal : SO supraoccipital ; /• jcO exoccipital ; BO basioccipital : I'tr
periotic ; ItS basisphenoid ; /'/ ptcrygoid ; AS alisphenoid ; OS orbitosphenoid ;
PS presphenoid : /'/ palatine ; I'o vomer ; MX maxilla ; PMx premaxilla :
sk stylohyal ; tk epihyal ; ch ceratohyal ; bk basihyal ; tk thyrohyal ; s symphysis
of mandible ; c/ coronoid process ; <-</condyle ; a angle ; id infenor dental canal ;
the mandible is displaced downwards to show its entire form ; the * indicates the
part of the cranium to which the condyle is articulated.

its structure will be best understood by commencing with
the description of the bones forming this axis.

1 When the zoologist wishes to throw into the strongest relief the
distinctive characters of different species, he selects for comparison fully
adult examples ; when the anatomist wishes to trace their community of
structure and their resemblances, younger specimens are better adapted
for his purpose.

n8 THE SKULL [CHAP.

When the skull remains in connection with the vertebral
column, it will be seen that its axis is a continuation for-
wards of the axis of that column, consisting of the bodies of
the vertebrae ; and that its hinder termination is placed in
the same line with the odontoid process of the second cer-
vical vertebra, the anterior termination of the axis of the
spinal column.

The large cavity above the axis of the skull (cerebral
cavity) is in direct continuity with the spinal canal above
the axis of the vertebral column.

Beginning at the posterior end of the axis, the section
will be seen to have passed through a flat, elongated bone
(Fig. 46, BO\ terminating freely behind at the inferior
margin of the great opening (foramen magnum} at the hinder
end of the cerebral cavity, by which this cavity is continued
into the vertebral canal, and through which the backward
prolongation of the brain (the medulla spinalis) passes. This
bone is the basiocdpital.

Immediately in front of this is a bone (the basisphenoid,
BS] not quite so elongated from before backwards, but of
greater vertical depth ; the interior being more or less
cellular in structure. The under surface is flat, but the
upper surface is hollowed in the middle, and raised at each
extremity. This hollow corresponds to the part called
" sella turtica " in the human skull, and lodges the pituitary
body of the brain.

Further forwards, and likewise separated by a vertical
fissure, is a bone (PS) of about the same length as the last,
but still more elevated, and very cellular within. Its in-
ferior contour is perfectly straight, but above it is somewhat
irregular. This is the presphenoid.

So far the cranio-facial axis consists of bones placed in
a continuous line, more or less depressed, and broad from

ix.] OF THE DOG. 119

side to side, and forming the floor of the cranial cavity ;
but the continuation of the axis forward is of a different
character. The anterior end of the presphenoid narrows
considerably, and the segment in front of it, in very young
skulls, is a much compressed vertical plate of cartilage, of
very considerable size, both from before backwards and
from above downwards. Ossification of this cartilage com-
mences in the posterior end and upper part, and spreads
forwards and downwards, but it never or very rarely reaches
its anterior extremity ; and in the animal now described a
narrow inferior margin remains jxjrmanently cartilaginous.
The ossified portion of this cartilage {ME} constitutes the
lamina ferpendicularis of the ethmoid bone, the anterior
unossified portion the septal cartilage of the nose, which is
the anterior termination of the cranio-facial axis. The
term mesethnwid may be applied to the whole of this element
of the skull, whether ossified or not.

Above all the posterior, or basicranial, part of this axis,
constituted by the three first-mentioned bones, is the cere
bral cavity, the walls of which constitute the " brain-case."

These walls are formed by several more or less expanded
and curved bones, which rise up from the sides of the axis
or floor of the cavity below, and, meeting in the middle line,
roof in the cavity above. These bones are arranged in
three sets from behind forwards, each corresponding with
one of the axial bones, and with the latter constituting one
of the three segments or bony rings into which the brain-
case may be divided.

The hindermost (or occipital) segment consists of the
basioccipital below ; next on each side the exocdpitah (EO),
and a large, median, flat bone above, with its upper ex-
tremity prolonged forwards in the middle line between the
bones of the next segment, called the supraocripital (SO).

120 THE SKULL [CHAP.

These four bones surround the foramen magnum behind, and
all take share in its circumference, though the exoccipitals,
which bound it laterally, contribute most. On each side of
the foramen, and rather below than above, are the occipital
condyles, by which the skull articulates with the first cervical
vertebra; and externally to these, separated by a deep de-
pression, is a prominent process for muscular attachments,
called the paroccipital (or paramastoid] process. The con-
dyles in the Dog are formed by the exoccipitals alone. The
part (IP] which appears to be an anterior prolongation of
the upper extremity of the supraoccipital, wedged in be-
tween the parietals, is ossified from a separate centre, and
in some animals remains permanently as a distinct bone. It
is then called intcrparietal.

The middle (or parietal) segment is formed by the
basisphenoid below. From the sides of this a pair of
wing-like bones (AS) extend outwards and upwards,
called alisphenoids ; and above these are large square-
shaped bones (/h), meeting in the middle line above, the
parietals.

The occipital and the parietal segments are in contact
below and above, but there would be a considerable open
space between them laterally were it not for the inter-
position of a group of bones, which do not form part of the
segmented wall of the brain-case proper, but are more or
less connected with the organ of hearing, and will therefore
be described hereafter. These are the bones which, being
all united into one in Man, constitute the so-called temporal
bone of human anatomy.

The anterior (or frontal) segment is formed by the pre-
sphenoid below ; then by the wing-like bor.es (OS} projecting
from its sides, smaller than those of the second segment,
called orbito sphenoids ; and finally by two greatly expanded

ix.] OF THE DOG. 121

bones (Ft), curving inwards above and in front, so as to close
in the cerebral cavity in these directions, by meeting in the
middle line. These are the frontal bones.

Between the middle bones of the parietal and frontal
segments (alisphenoid and orbitosphenoicl) is an irregular
vacuity, called the foramen lace rum a uteri us, or sphenoidal
fissure, through which several nerves pass to the orbit. This
is the second vacuity in the side wall of the skull, the first
being the one between the occipital and parietal segment,
partially filled by the periotic bone.

As the occipital segment is not closed behind, so in the
same way the frontal segment is open in front, the aperture
being bounded by all the bones which enter into its com-
position— presphenoid, orbitosphenoids, and frontals. The
hinder edge of the mesethmoid rising up to meet the
frontals makes a median partition (the crista galli of human
anatomy) to this aperture, which is further closed by a
special ossification (CE) connected with the org.in of smell,
the cribriform />/<//<?.

Thus the brain case may be described as a tube, dilated
in the middle, composed of three bony rings or segments,
with an aperture at each end, and a fissure or space at the
sides between each of the segments.

The cranial cavity thus formed is of a general oval form,
but broader behind than in front. The floor is compara-
tively straight ; the upper surface arched. It is imperfectly
divided by bony ridges into three compartments. The
most posterior of these, marked off in front by a sharp
ridge along the periotic bone (Per), extending from near the
junction of the basisphenoid and basioccipital, upwards,
outwards, and backwards, along the line of junction of
the parietal and supraoccipital, and strongly marked by an
inward shelf-like projection from the former (the ossified

122 THE SKULL [CHAP.

tcntorium cerebelli], is called the cercbellar fossa, as it
lodges the division of the brain named "cerebellum." The
most anterior and smallest compartment is marked off by a
vertical ridge on the orbitosphenoid and the frontal. Its
walls are chiefly formed by the cribriform plate. This is the
olfactory fossa (rliinencephalic fossa, Owen), for the lodgment
of the olfactory lobe. Between these two is the great cere-
bral fossa, in which the hemisphere of the cerebrum lies.
This is very imperfectly divided below into two compart-
ments, by a slight ridge at the hinder edge of the orbito-
sphenoid and continued thence outwards at the junction of
the frontal and alisphenoid. This ridge corresponds with
the Sylvian fissure of the brain ; the part of the cerebral
fossa in front of it lodges the frontal lobe of the cerebrum,
that behind it the temporal lobe.

Through the lateral parts of the floor of the cranial cavity
are various perforations, or foramina, either holes passing
directly through the bones, or vacuities occasioned by want
of contact, for a limited space, of contiguous bones. These
are mainly for the purpose of allowing of the exit of the
various nerves which take origin from the brain ; and as
they are extremely constant in their position, and offer useful
landmarks for determining the homologies of the bones
throughout the vertebrate series, it is important that they
should be well known. (See diagram at p. 126.)

1. The most anterior is the space, before spoken of, in
front of the anterior segment, occupied by the hinder part
of the ethmo-turbinal, commonly called the " cribriform
plate." The numerous perforations in this plate transmit
the olfactory nerves arising from the olfactory lobes.

2. Near the hinder border of the orbitosphenoid is a con-
spicuous, nearly round hole, through which the optic nerve
passes, and hence called optic foramen.

ix.] OF THE DOG. 123

3. At a very short distance behind this is a more irregular
oval opening, between the orbitosphenoid and the ali-
sphenoid. This is the sphenoidal or orbital fissure, or
foramen lacerum anterius. It leads into the orbit, and
allows the exit of the motor nerves of the eyeball, or third,
fourth, and sixth cranial nerves, and also the first division
of the trigeminal or fifth nerve.

4 and 5. The alisphenoid near its base is perforated by
two foramina : the anterior small and somewhat round, the
posterior larger and oval ; these are the foramen rotntnhtm
and \\\z foramen male, and transmit respectively the second
and third divisions of the fifth nerve.

6. Between the alisphenoid anil the exoccipital is a large-
space, almost entirely filled by the bony capsule of the organ
of hearing, the periotic bone. In front of the inner end of
this bone is an opening (foramen lacerum medium faisis
cranii), through which the internal carotid artery sometimes
enters the craninl cavity.

7. Near the middle of the inner surface of the periolic
is the meatus anditorius infernus, into which the seventh
and eighth nerves enter : the former (the facial nerve)
passes through the bone and emerges on the other side
(by the stylo-tnastoid foramen] ; the latter, the auditory, is
distributed to the internal organ of hearing within the
periotic bone.

A deep depression seen above the internal auditory
meatus, and of nearly the same size, is not a foramen but a
fossa, lying within the concavity of the superior semicircular
canal. It lodges the flocculus, a small process of the cere-
bellum.

8. Between the periotic and the exoccipital an irregular
space is left (the foramen lacerum poster tus), through which
the glossopharyngeal, pneumogastric, and spinal accessory

124 THE SKULL [CHAP.

nerves (the ninth, tenth, and eleventh) pass out of the
cranium.

9. The exoccipital is perforated, a little in front of the
condyle, by the condylar foramen, which gives exit to the
twelfth, or hypoglossal, nerve.

10. Lastly, the large median opening, behind the bones
of the posterior segment of the skull, is the fora men magnum.
through which the spinal cord passes out.

It will be seen from the foregoing description that the
three organs of special sense, situated in the walls of the
cranium, have definite relations with the three osseous
segments. The first, or organ of smell, is situated in front
of the frontal segment ; the second, or organ of sight,
receives its nerves by apertures situated between the frontal
and parietal segments or perforating the former; the third,
or organ of hearing, is intercalated between the parietal
and occipital segment.

The portion of the skull anterior to the junction of the
presphenoid and the mesethmoid constitutes the face. This
differs entirely from the cranial cavity in having a complete
median partition, and consists mainly of two tubular cavities
placed one on each side of this partition. These are the
nasal cavities. They are open at each end, the orifices
being termed respectively anterior and posterior nares.

Each of these elongated cavities is deepest vertically in
its posterior part, where it is partially divided into an upper
and lower chamber : the upper one, the olfactory chamber,
being closed behind by the cribriform plate ; the lower, the
narial passage, terminating in the posterior nares.

Each nasal cavity may be described as having an inner
wall, an outer wall, a floor, and a roof.

The inner wall is formed mainly by the partially ossified

ix.] OF THE DOG. 12.5

mcsethmoid cartilage (ME), but the lower part of the pos-
terior two-thirds also by the vomer ( Vo). The greater part
of this bone has the form of a trough, hollow above, em-
bracing the inferior, thickened border of the mesethmoid
cartilage, and extending a little way behind this so as also
to underlie the anterior portion of the presphenoid ; but it
also develops from its under surface in the middle line a
thin plate, which passes vertically down to the centre of
the floor of the nasal passages, and completes the septum
inferiorly.

Above, rather behind the middle of the bone, the lateral
plates of the vomer, which embrace the mesethmoid carti-
lage, send out sideways a pair of wing-like processes, which
join the side walls of the nasal cavity, and form the partial
horizontal partition, dividing the narial passage from the
olfactory chamber.

The outer wall of the nasal cavity is formed mainly by
four bones : (i) a somewhat quadrate, thin, nearly vertical
plate of bone (/V), the pterygoid, attached above to the under
surface of the basisphenoid and presphenoid, supported
externally by a strong descending process of the alisphen-
oid, the- external pterygoid plate, ending posteriorly and
inferiorly by a free border, and articulating in front with (2)
the palatine. This bone (7Y) is of much greater extent ; for,
besides its vertical portion, forming the outer wall of the
nasal canal in front of the pterygoid, it sends from its upper
edge a lamina inwards to meet the horizontal plate of the
vomer, and aid in forming the roof of the hinder part of the
narial passage. It also sends a strong horizontal lamina
inwards from its lower edge, which, meeting its fellow in the
middle line, forms the posterior part of the floor of the narial
passage. In addition to these it sends a broad plate upwards
and forwards in the inner wall of the orbit.

[Continued on p. 128.

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128 THE SKULL [CHAP.

3. In front of this is the maxilla (Mx], a still more con-
siderable bone. It not only forms the chief part of the outer
wall of the nasal cavity, but it also sends inwards a hori-
zontal plate, forming the middle part of its floor. At the
junction of its vertical and horizontal portions is the alveolar
border, in which the canine, premolar, and molar teeth are
lodged.

4. The most anterior bone of this series is the premaxilla
(PMx), which also has an ascending or vertical plate,
forming the outer wall of the nasal cavity, and a horizontal
plate forming the anterior part of its floor ; at their junc-
tion its alveolar border lodges the incisor teeth. The pre-
maxilla forms the outer and lower boundary of the anterior
nares.

Besides these four, there is a small bone which enters into
the outer wall of the upper part of the nasal cavity, between
the ascending process of the palatine, the maxilla and the
frontal. This is perforated by the duct, which conveys the
tears from the orbit into the nasal cavity, and is hence
called la cry in al.

Above this a process from the frontal completes the
upper and posterior part of the outer wall of the olfactory
chamber.

The floor of the nasal cavity is formed, as above said, by
the horizontal plates of the palatine, maxilla, and premaxilla
meeting the corresponding bones of the opposite side in the
middle line. The inferior surface of this same horizontal
layer of bone is the roof of the mouth, or bony palate.

The roof of the nasal cavity is formed, posteriorly by
the continuation of the frontal forwards beyond the cere-
bral cavity, the " nasal process of the frontal" but mainly
by a long narrow bone, the nasal bone (^Vtf). The hinder
extremity of this lies upon the nasal process of the frontal ;

ix.] OF THE DOG. 129

its anterior end is free, and forms the upper boundary of
the anterior nares ; its outer side is in contact with the
frontal, maxilla, and premaxilla ; and its straight inner edge
lies against that of the corresponding bone of the opposite
side.

Within each nasal cavity are two very singular bones,
each being composed of a number of delicate lamella;
folded and arranged in an exceedingly complex manner,
forming a mass with so many passages and perforations that
the term " spongy bones " has been applied to them.

The most posterior is the larger, and placed rather higher
than the other, its anterior extremity (ET) overlapping it.
It completely fills the proper olfactory chamber ; its hinder
extremity occupying the gap left in the cranial wall in front
of the anterior segment of the brain-case. The various
laminae are all connected together and to the hinder end of
the mesethmoid, by a plate of bone (CE) so full of perfora-
tions of varied form and si/e that it is called the cribriform
plate, and from it the name of ethmoid (or sieve-like) is
commonly .applied to all the bony structures with which
it is united. On their outer side these laminae are con-
nected to a thin flat plate of bone (the so-called os planum}
which lies against the inner wall of the maxillary, but does
not ordinarily contract any union with it.

This bone results from the ossification of the complexly
folded cartilage, over the surface of which the olfactory
nerves are spread, the division into laminae permitting a
great increase of sensitive surface. As, although originally
distinct, it subsequently unites with the mesethmoid, by
means of the cribriform plate, it is considered in human
anatomy as part of the same bone, and described under
the name of "lateral mass of the ethmoid," being further
divided into the superior and middle " turbinated bones " ;

K

i3o THE SKULL [CHAP.

but the name ethmoturbinal, applied to it by Sir Richard
Owen, is perhaps more appropriate.

The uppermost of the lamellae of the ethmoturbinal, lying
immediately under the nasal bones, is rather distinct from
the others, and extends much further forwards ; and as in
certain Mammals it becomes united by bone with the
nasal, it is sometimes distinguished under the name of
nasoturbinaL

In front, and on a rather lower level, a similar, but smaller
and less complex bone (AfT), consisting chiefly of horizontal
lamellae, is placed. This, though originally developed from
the same cartilage lining the outer wall of the nasal chamber
as the last, ossifies quite distinctly from it, and contracts a
bony union by a horizontal lamella on its outer side with
the maxilla. This is the maxiUoturbinal, and corresponds
with the " inferior turbinated bone " of human anatomy.

It will be observed, that while the ethmoturbinal is placed
high in the nasal cavity, and above the direct channel by
which the air passes to the posterior nares, the maxiUo-
turbinal, situated nearer the front of the chamber, before it
has divided into an upper true olfactory chamber and a
lower narial passage, nearly blocks up the whole cavity, so
that air passing through in inspiration is filtered between its
meshes. The moist membrane which covers its bony plates
in life is supplied with nerves chiefly from the fifth pair,
and not from the olfactory ; so that it does not perform the
function of an organ of smell like the ethmoturbinal, but
rather serves to guard the entrance of the respiratory
passages from foreign substances, and perhaps to warm the
inspired air.

In describing the walls of the cranium, a large space was
mentioned on each side, between the posterior and middle

ix.] OF THE DOC. 131

cranial segment, in which were inserted certain bones not
yet noticed. These bones form a definite group by them-
selves, at all events locally connected, though very different
in function and structure.

In a mass of cartilage, in the position just indicated,
ossification takes place from several centres (three, called
respectively pro-otic, ebiotic, and opisthotic, according to
Professor Huxley and others, in the human skull;1 but the
process has not been accurately traced in other Mammals).
These very rapidly unite to form a single bone, which com-
pletely encloses the labyrinth or essential organ of hearing,
consisting of the vestibule, semicircular canals, and cochlea.
This bone is the periotic (Pfr). It is divided into two por-
tions : an antero-internal, which forms a somewhat angular
projection within the cranial cavity, and is of remarkable
density — the petrous portion ; and a postero external, a sort
of process from the former, smaller, less dense, and forming
a small portion of the wall of the cranium, appearing
externally just in front of the exoccipital— the mastoid
portion.

The petrous is of course the more important, and has
constant characters throughout the class, while the mastoid
is very variable, and sometimes can scarcely be said to exist.
It is in no case a separate bone ; and, although a portion of
it may develop originally from a separate centre, it is always
before birth firmly united with the petrous, so that they
will be spoken of here as one bone, under the name of
periotic.

The essential characters of the petrous portion of the
periotic are, that it contains within it the internal ear ;
that it has on its inner or cranial side a foramen, through
which the facial and the auditory nerves leave the cranial

1 " Elements of Comparative Anatomy," (1864), p. 148.
K 2

132 THE SKULL [CHAP.

cavity, the former to pass through the bone, escaping by
the stylomastoid foramen on the outer and under surface,
the latter to be distributed on the sensitive portions of the
organ of hearing ; and that it has on its outer side two
holes, one placed above the other, the fenestra ovalis and
the fenestra rotunda, through which the internal ear com-
municates with the cavity of the tympanum, or middle-ear,
which is situated on the outer side of the petrous part of
the periotic bone.

Externally to the periotic bone are placed two bones
separately developed in fibrous tissue, which often acquire a
very close connection with the periotic, occasionally, as in
Man, becoming firmly ankylosed with it.

The upper one of these is the squamosal (Figs. 48 and 49,
Sy), which has a broad, scale-like, vertical portion spreading
out over the side of the cranial wall, uniting with the supra-
occipital behind, overlapping the lower edge of the parietal
and the hinder part of the alisphenoid, and also appearing
for a very small space in the inner side of the cranial wall.
From near its lower border it sends a strong process out-
wards, which soon curves forwards, called the zygomatic
process. This articulates with another bone ( Ma), the malar
or jngal, which connects it with the maxilla, and so forms
the strong, lateral, nearly horizontal, or slightly arched
osseous bridge, which passes from the face to the hinder
part of the cranium, called the zygomatic arch. On the
under surface of the base of the zygomatic process of the
squamosal is a laterally extended, oblong surface, concave
from before backwards, for the articulation of the condyle
of the lower jaw, called the glenoid fossa (gf\ the hinder
edge of which is projected into \\\Q postglenoid process (gp).

The lower bone, on the outer side of the periotic, is
the tympanic (TV). At birth this .is a mere osseous ring,

ix.] OF THE DOG. 133

incomplete above, surrounding the inferior three-fourths of
the membrana tympani, but it undergoes a considerable
development in the course of the first few months. The
external edge of the ring is produced horizontally outwards
to form the short, bony, external auditory meatus ; while
the under and inner surface is greatly expanded, to form
the conspicuous rounded prominence, hollow within, called
the auditory bulla, which abuts against the outer edge of
the basioccipital below.1

The space that is left among this group of bones —
bounded by the periotic (the part in which the before-
mentioned fenestne are situated) within, the periotic and
squamosal above, the tympanic and its bullate expansion
below, behind, and in front, and by the meatus auditorius
externus closed in the natural state by the membrana
tympani, to the outer side — is called the tympanic carity.

It contains within it the ossicula auditus, three small bones
called malleus, incus, and stapes, which articulated together,
stretch across the cavity from the membrana tympani to the
fenestra tn-alis.- The cavity has an opening at its antero-

1 The whole of the bulla is generally considered as belonging to the
tympanic bone, but its inner part in many Mammals is developed in a
distinct cartilaginous lamella, interposed between the lower edge of the
tympanic ring and the base of the skull. This may ossify from a sepa-
rate nucleus, or by extension of bony deposition inwards from the true
tympanic The development of this region of the skull in the Mam-
malia still offers an interesting field for investigation,

* As these bones are, in the Mammalia, completely sul>servient to
the organ of hearing, their modifications will not be described in the
present work. A very detailed and fully illustrated account of them
has been given by Alban Doran in the Transactions of the Linnean
S<>cietyt Second Series, vol. i. " Zoology," 1879.

Much has been written on the still unsettled question of the develop-
ment and the homologies of the auditory ossicles by ReUhert, Peters,
Huxley, Parker, Koelliker and Gegenbaur ; see also IV. Saltmky,

I34 THE SKULL [CHAP.

internal angle, through which the Eustachian tube connecting
the tympanum with the pharynx passes.

The inner side of the bulla is perforated lengthwise by a
canal, which commences posteriorly within the margin of
the foramen lacerum posterius (between the auditory bulla
and the exoccipital), and transmits the internal carotid artery.
This vessel appears again on the surface, at the anterior
extremity of the bulla, close to the Kustachian orifice ; then
runs upwards and inwards and enters the cranium through
the foramen lacerum medium.

This completes the enumeration of the bones of the
cranium. Before proceeding further, it will be desirable to
take a general survey of this part as a whole, pointing out
the most prominent features of its various surfaces.

The posterior surface is, in a general sense, a vertical wall
somewhat triangular in form, broad below and pointed above.
In the middle line, at its lowest border, is the nearly round
foramen magnum, bounded by the supraoccipital above, the
exoccipitals on each side and the basioccipital below. On
the sides of the foramen magnum, and approaching each
other in the middle line below, but diverging above, are
smooth eminences, the occipital condyles. Further outwards,
and separated from these by a deep valley, are the par-
occipital processes, projecting backwards and downwards.
Outside of the upper part or origin of these processes, the

"Beitrage zur Entwicklung. der knorpeligen gehorknochelchen. "
Morphol. Jahrb. VI. 1880. Fraser, "On the Development of the
Ossicula Auditus of the higher Mammalia," Philosoph. Transact, vol.
173, 1883, p. 901. /'. Albrecht, " Sur la valeur morphologique ck-
1'articulation mandibulaire, &c.," Bruxelles, 1883. M. L. Dallo, "On
the malleus of the I.acertilia, and the malar and quadrate bones of
Mammalia," Quart. Journ. Micru.sc. Science, vol. xxiii. N. 8. p. 579,
1883. The last contains a complete list of the literature on the subject
and a tabular arrangement of the views held by previous authors.

ix.] OF THE DOG. 135

mastoid portion of the periotic appears on the hinder wall of
the skull The remainder of the region is formed by the
supraoccipital, and it is distinctly marked off laterally by
ridges, which, commencing in the median line above, runs
downwards and outwards, at the junction of the parietals and
supraoccipital, and are continued on the squamosal in front
of the mastoid to the upper edge of the external auditory
meatus. The ridges of each side taken together form the
lambdoid or occipital crest. They are far more conspicuous
in old than in young animals.

The superior surface of the skull (Fig. 48) may be divided
into a cranial and facial portion. The former is of a some-
what oval form. On its upper surface posteriorly, in full-
grown dogs, is a median ridge joining behind with the
superior angle of the occipital crest, and dividing anteriorly
into two less elevated ridges which curve outwards to the
superior posterior angle of the orbit. This ridge, as long as
it is single and median, is called the sagittal crest. It bounds
superiorly a large surface on the side of the skull, limited
behind by the occipital crest, and below by the zygoma,
called the '' temporal fossa," from which the temporal muscle
takes its origin. In young dogs the upper boundary of the
surface for the origin of this muscle is of less extent, not
reaching so high as the middle line of the cranium, and is but
obscurely indicated on the comparatively smooth surface of
the skull. As the muscle increases in development its surface
of origin gradually ascends until it reaches the middle line,
and with advancing age a still larger space is afforded for it
by the gradual growth of the sagittal crest.

These changes in the upper part of the skull during growth
have been particularly noticed, because they take place in very
many animals, and, without altering in the least the actual
form of the brain-case give rise to a very different external

THE SKULL

[CHAP.

appearance of the skull, either in members of the same
species, or in different but allied species.

The upper part of the skull, in front of the diverging
boundary lines of the temporal fossa, is expanded and some-

Fr;. 48.— Upper surface of cranium of a Dog, J. SO supra-occipital; IP inter-
parietal ; Pa parietal ; Sq squamosal ; Fr frontal ; Ma malar ; L lacrymal ;
.l/.r maxilla ; A'a nasal ; PMx premaxilla : tip anterior palatine foramen ; to infra-
orbital foramen ; pof postorbital process of frontal bone.

what flattened, and has on each side a triangular process
(pof\ which curves somewhat downwards, and indicates the
division of the temporal fossa behind from the orbit in front.

ix.] OF THE DOC. 137

This is the postorbital process of the frontal bone. It is con-
nected by a ligamentous band, in the living animal, with a
corresponding process arising from the zygoma ; but when
this is removed the orbit and temporal fossa are widely
continuous, their respective limits being only indicated by
the above-mentioned processes.

The face is produced considerably in front of the orbits,
and not only becomes more depressed, but also more com-
pressed laterally, and is obliquely truncated anteriorly,
terminating in the rounded incisor border of the premaxilla
(PMx); above which is placed the subcircular orifice of the
anterior nares.

The upper, and a considerable portion of the lateral surface
of the cranium behind is formed by the parietal bones (Pa),
having the narrow interparietal (//*) ankylosed with the supra-
occipital (SO), extending between them for about half their
length. In front of this the parietals are commonly united
together by bone in old dogs.

Anteriorly to the parietals, the upper part of the temporal
fossa, the frontal plateau between the orbits, and the upper
half of the inner wall of the orbit, are formed by the frontal
bone. The remaining or lower portion of the temporal fossa
is formed by the squamosal behind and by the alisphenoid
in front On the inner or cranial surface of the confluent
orbital and temporal fossae, a wide groove runs obliquely
downwards and backwards, which may be considered as the
boundary lines of these two regions. In the lower part of
this groove are several large foramina placed in linear series.
The highest is the optic foramen, the next (of larger sue) the
sphenoidal fissure, and the third the foramen rotundum and
anterior opening of the alisphenoid canal. The orbit has no
floor except for a very short space in front ; the lower border
of its inner wall passing directly into the outer surface of the

138 THE SKULL [CHAP.

vertical ridge formed by the pterygoid, the pterygoid process
of the alisphenoid and the palatine bones, and continuing the
outer wall of the narial passage backwards beyond the bony
palate. The palatine bone forms a considerable part of
the inner wall of the orbit, joining the frontal anteriorly
though separated from it for a considerable space posteriorly
by the orbitosphenoid. The lacrymal (L) appears in the
anterior boundary of the orbit, the malar (Ma) joins its outer
boundary, and the upper surface of the hinder end of the
alveolar border of the maxilla projects backwards, so as to
form a partial floor to its anterior extremity. In front of
the orbits the face is formed above by the long narrow nasals
(Na) pointed behind, and widening and obliquely truncated
in front to form the upper border of the narial aperture ; on
each side by the maxillae (Jlfx) having near the middle oi
their surface the large infraorbital foramen (/<?), through
which the terminal branches of the second division of the
fifth or sensory nerve of the face pass to be distributed to the
upper lips and whiskers ; and quite anteriorly by the pre-
maxillae (PMx\ which complete the boundaries of the nares,
and send up narrow processes between the nasals and
maxillae towards, though not meeting with, similar processes
which run from the frontals.

The inferior surface of the skull (Fig. 47) is formed an-
teriorly by the nearly flat, elongated surface of the palate,
narrower in front than behind, composed anteriorly of the
premaxillae (PMx) ; then of the maxillae (Mx), which diverge
posteriorly and allow the palatines (PI) which form the
hinder border to reach in the middle line almost to the
centre of the palatal surface. In front and at the sides this
surface is bounded by the alveolar borders of the premaxillae
and maxillae in which the teeth are set. Anteriorly are two
considerable oval foramina (#//), placed longitudinally very

IX.]

OF THE DOG.

139

near the middle line, formed mainly in the premaxillae,
though their boundary is completed posteriorly by the

FIG. 49. — Under surface of the cranium of a Dog. J. SO siipraoccipital : ExO
exoccipital ; BO basioccipital ; Per mastoid portion of periotic ; Ty tympanic
bulla : BS basisphenoid : Sq zygom.it ic process of squamosal ; Ma malar ; - 1-V
alisphenoid: ft pterygoid : PS presphenoid ; Ar frontal; Vo vomer \Pl palatine
MX maxilla ; PMx premaxilla ; fin foramen magnum ; oc occipital condyle
// paroccipital process ; cf condylar foramen ; flp foramen lacerum posterius ; nn
stylo-mastoid foramen ; earn external auditory meat us ; pgf postglenoid foramen
gp postglenoid process ; gf glenpid fossa;///* foramen lacerum medium \ fo
foramen ovale ; its posterior opening of alisphenoid canal ; fr foramen rotundum
and anterior opening of alisphenoid canal ; sf sphenoidal fissure or foramen
lacerum an terms ; op optic foramen ; ///" posterior palatine foramen ; apf anterior
palatine foramen.

maxillae ; these are the anterior palatine or incisive foramina.

140 THE SKULL [CHAP.

The naso-palatine nerve descends through them to spread
over the anterior surface of the soft palate. Not far from
the hinder border of the palate, and more distant from the
middle line, near the suture between the maxilla and palatine,
are several much smaller foramina (posterior palatine), also
for the transmission of branches of the fifth nerve and blood
vessels.

The truncated median part of the hinder edge of the
palate forms the lower margin of the posterior narial aperture.
Laterally, the palate bones are continued backwards as
vertical plates, thick and rounded below at first, but gradually
becoming more compressed. These are continued still
further backwards by the compressed pterygoid bones (Pt),
ending in the backward projecting hamular processes, and
supported externally by the descending (pterygoid) plate of
the alisphenoid. The groove between these descending
lamellae of bone continues the narial passage backwards. It
has for its roof the vomer ( Vo] in front, then the presphenoid
(PS), and posteriorly a portion of the basisphenoid (BS) ',
but the palatines and pterygoids arch over so much towards
the middle line that they only leave a small strip of these
bones exposed. Inferiorly, this groove is not closed by
bone, but in the living animal the soft palate is stretched
across it.

The base of the skull, behind this " mesopterygoid " fossa
presents in the middle a nearly flat elongated surface, con-
sisting of the basisphenoid (-BS) and basioccipital (-BO] ; the
latter, roughened for the attachment of muscles and ter-
minating posteriorly at the inferior border of the foramen
magnum (////), flanked on each side by the occipital
condyles (oc). The nearly straight lateral edges of the
anterior half of the basioccipital rise up to abut against the
prominent smooth rounded auditory bullce (Tj), which form

IX.] OF THE DOG. 141

so conspicuous a feature in this region of the skull, and
which are produced outwards into the lower wall of the
external auditory meatus (tarn}. In the antero-internal angle
of the bulla is seen the irregular orifice of the Eustachian
canal. Close to the inner side of this is an oval aperture
which is at the same time the anterior extremity of the carotid
canal and the entrance to the foramen lacerum medium (/////)
through which the internal carotid artery enters the cranial
cavity. In front, and rather to the outer side of this, is the
foramen ovale (fo) piercing the alisphenoid, and immediately
before this is a round aperture (as) leading to a short canal
running horizontally forwards through the same bone at the
root of its pterygoid process, and opening anteriorly into the
foramen rotundum (fr). Through this the external carotid
artery runs lor part of its course, and it has been called the
alisphenoid canal. *

In front of the outer side of the auditory bulla' is the
glenoid fossa for the articulation of the mandible, bordered
behind by the conspicuous curved postglenoid process (.<?/).
Immediately behind this the root of the zygoma is pierced
by a large hole, postglcnoid foramen ( f>gf), through which a
vein passes out from the lateral sinus within.

Behind the auditory bulla, to the inner side, is the large
foramen lacerum paste rius (///), and situated deeply within its
recesses, the posterior opening of the internal carotid canal.
On a ridge of the exoccipital, between this large foramen
and the depression immediately in front of the condyle, is
the small, nearly circular condy la r foramen (cf\ and at the
outer termination of the same ridge rises the conical paroc-
cipital process (//>), abutting at its base against the hinder

1 See H. N. Turner's " Observations relating to some of the Foramina
in the Base of the Skull in Mammalia," &c., Proc. Zool. Soc. 1848,
p. 63.

1 42 THE SKULL [CHAP.

end of the auditory bulla. Immediately behind the bulla,
and to the outer side of the abutment of the paroccipital
process against it, is an oval hole (sm\ partially divided by
a constriction into an inner and an outer division. In
the inner division the end of a small cylindrical plug of
bone, the tympanohyal, can generally be seen. The outer
division is the stylomastoid foramen, through which the
seventh nerve, or portio dura, makes its exit. The bone
forming its outer boundary is the mastoid portion of the
periotic.

Connected with the posterior lateral parts of the cranium
are two appended bony parts : the lower jaw or mandible,
and the hyoidean apparatus. The former forms the frame-
work for the floor of the mouth, and supports the lower
series of teeth ; the latter gives a firm yet movable point
of attachment to the root of the tongue and to the larynx,
or organ of voice.

The mandible consists of two symmetrical elongated rami
(see Fig. 46, p. 117), diverging behind, and coming in contact
in front at the middle line, by a roughened surface called the
symphysis (s) ; here they are firmly held together by inter-
posed fibrous tissue, or in old animals they may become
ankylosed.

Each ramus is compressed from side to side, has a
thickened rounded lower border, slightly curved in the
longitudinal direction, and a nearly straight upper alreolar
border, in which the teeth are implanted. The inferior
border inclines upwards in front to meet the alveolar border
at the front of the symphysis. Near the posterior extremity
is the condyle (cd), a transversely-extended projection, with its
upper surface rounded in the antero-posterior direction, and
which, fitting into the glenoid cavity of the squamosal bone,
forms the hinge-like synovial articulation by which the lo\ver

ix.] OF THE DOG. 143

jaw moves on the skull. The upper border, between the
condyle and the hindermost tooth, rises into a high, com-
pressed, recurved process (the coronoid process, cp), to which
the temporal muscle is attached. The outer surface of this
process gradually subsides into a considerable hollow in the
side of the ramus, with prominent anterior, inferior, and
posterior edges, to which the masseter, another powerful
muscle for closing the jaw, is attached.

The point at which the vertical hinder edge of the ramus,
descending from the condyle, meets the horizontal inferior
border, is called the angle, which in the Dog is prolonged
into a conspicuous compressed process with an upturned and
slightly inverted pointed extremity, the angular process (a).
On the inner side of the ramus, a little way in front of and
below the condyle, is the inferior dental foramen (id), for the
admission of the inferior dental nerve (from the fifth pair)
and artery. On the outer side of the ramus, near its anterior
extremity, is the mental foramen, through which a branch of
the same nerve passes out to the lower lip and surrounding
structures.

The hyoidean apparatus (Fig. 50) consists of a median
portion below, the basihyal (bK), from which two pairs
of half arches, or " cornua," extend upwards and outwards.
The anterior (ch to s/i) is the largest, and connects it with
the cranium. The posterior (//;) is united externally or
superiorly with the thyroid cartilage of the larynx. In the
Dog there are four distinct ossifications in the anterior arch.
The first is a small cylindrical piece of bone lying in a
canal between the tympanic and periotic bones, immediately
to the inner and anterior side of the stylomastoid foramen,
and by its upper end firmly ankylosed with the surround-
ing bones. It can be seen much more distinctly in
some dogs' skulls than others, and is more conspicuously

144 THE SKULL [CHAP.

developed in some other Mammals. This I have called tym-
panohyal, as it is always in relation with the hinder edge
of the tympanic bone, generally more or less surrounded by
it, and it extends upwards, embedded in, and afterwards
ankylosed with, the periotic, to the hinder wall of the
tympanic caviiy. Its lower end is truncated and con-
tinued into a band of cartilage, which connects it with
the proximal end of the bone which has been generally
recognised as the uppermost of the series forming the

6/i

FIG. 50. — Extracranial portion of hyoidean apparatus of Dog, front view, sh stylo-
hyal ; eh epihyal ; ch ceratohyal (these three constitute the "anterior cornu");
b'k basihyal or " body " of hyoid ; th thyrohyal, or "posterior cornu."

anterior hyoidean arch, the stylohyal (s/i). The two suc-
ceeding bones (ep and ch} are named by Sir Richard Owen
respectively epihyal and ceratohyal. All three are elon-
gated, compressed, slightly curved or twisted on them-
selves, tipped at each end with cartilage, and connected
with each other by synovial joints. The stylohyal and
epihyal are nearly equal in length, the ceratohyal shorter
and stouter.

The basihyal (bit] is a transversely-extended, flattened bar,

IX.] DEVELOPMENT, 145

with its extremities rather upturned and thickened. The
posterior cornu (th) consists of a single, nearly straight,
compressed bone, the thyrohyal, articulated inferiorly with
the outer end of the basihyal, just below the attachment
of the ceratohyal, and truncated at its superior extremity,
to which the thyroid cartilage of the larynx is suspended.

Development of the Skull. — For a detailed and beautifully
illustrated account of the early development of the Mam
malian skull, we must refer to Professor Parker's monograph
"On the Structure and Development of the Skull in the
Pig" {Philosophical Transactions, 1874). As however the
prevailing views regarding the morphology of the skull have
been considerably modified even since the publication of
that memoir, we take the following abstract from Balfour's
Treatise on Comparative Embryology, 1881.

The primitive cartilaginous cranium is formed by a
differentiation within the membranous cranium, and is
composed of the following parts :

(i.) A pair of cartilaginous plates on each side of the
anterior extremity of the notochord, known as the para-
chordals (Fig. 51, pa. ch.}. The continuous plate, formed
by them and the notochord, is known as the basilar or
basicranial plate.

(2.) A pair of bars forming the floor for the fore-brain,
known as the trabeculae (tr) ; these are continued forward
from the parachordals. They meet behind and embrace the
front end of the notochord ; and after separating for some
distance bend in again in such a way as to inclose the
pituitary body (py). In front of this they coalesce, and
together with the olfactory capsules (ol) give rise to the pre-
sphenoidal and ethmoidal regions of the cranium (Fig. 47, 1.).

(3.) The cartilaginous capsules of the sense organs. Of
these the auditory and olfactory capsules unite more or less

146

THE SKULL.

[CHAP.

intimately with the cranial walls. The basicranial plate
grows up as an arch over the occipital region of the skull,
and coalescing with the auditory capsules gives rise to the
primordial skeleton of the occipital, periotic, and basi-
sphenoidal regions of the skull : the parietal and frontal
regions being afterwards completed by ossification in mem-
brane surrounding the cranial cavity.

FIG 51. — Klements of skull (seen from below) of an embryo Pig two-thirds of ;in
inch long, fn.ch parachordal cartilage; tic notochord ; au auditory capsule ; py
pituitary body; tr trabeculai ; c.tr trabecular cornu ; /« prenasal cartilage; en
external nasal opening ; ol nasal capsule ; j>.f>g palatopterygoid tract inclosed in
the maxillopalatine process; mn mandibular arch; ky hyoid arch; th.h first
branchial arch ; ya facial nerve ; 8a glossopharyngeal; ?>b vagus ; 9 hypoglossal.

Besides the parts composing the cranium proper, the
Mammalian skull is completed by the labial cartilages, the
meaning of which is still very obscure, and a series of three
paired descending cartilaginous bars or arches, developed in
the visceral laminae, constituting the sides of the face and
neck.

The first visceral (mandibular) arch divides itself into
a short proximal or dorsal, and a much longer distal or
ventral end (Meckefs cartilage}. The first sends out
forwards towards the roof of the mouth-cavity, a process

ix.] DEVELOPMENT. 147

(pterygo-palatine} which gives rise to the pterygoid, palatine,
maxillary and malar regions (Fig. 47, II.).

The latter, Meckefs cartilage (Fig. 52, mk ; Fig. 47, III.), a
slender rod, is proximally in relation with the periotic region
of the skull. In the Mammalia, the upper extremity of this
rod becomes converted into the malleus, one of the small
bones in the tympanic cavity, while in connection with the
lower or distal part, the ramus of the mandible or lower jaw
is developed, partly by conversion of the cartilage itself, but
principally by the ossification of fibrous or cartilaginous
tissue deposited around it. The upper end of the ramus

v

Ku;. 52. — Side view of mandibular and hyoid arches of an embryo Pig, an inch and
a third long. The main arch i« seen as displaced backwards after segmentation
from the incus, tg tongue ; mk Meckelian cartilage ; ml body of malleus : ntl>
mnnubrium or handle of the malleus; t.ty legmen tympani ; /'incus: tt stapes :
if>y interhyal ligament ; st.h stylohyal cartilage ; It.h hypohyal ; bh basi-branchial ;
th.k rudiment of first branchial arch ; ^a. facial nerve.1

afterwards acquires a secondary articular connection with
the squamosal bone, its primitive connection with the
malleus entirely disappearing.

The rod of cartilage forming the second visceral arch
(Fig. 47, IV.) becomes the anterior hyoid arch, its proximal
extremity being modified into the incus.

From the third arch, which corresponds to the first
branchial of branchiate vertebrates, is formed the posterior
hyoid arch, or thyrohyal (th.li) (Fig. 47, V.).

1 Figs. 51 and 52, reduced from the original figures of Parker, are
taken with permission from Balfour's Comparative Embryology.

L 2

148 THE SKULL. [CHAP.

The "cleft" between the palato-pterygoid (II.) and the
mandibular (III.) bar is the mouth. The first true cleft,
however, is the one between the mandibular and the anterior
hyoid arch (IV.). It becomes contracted into the Eustachian
tube, tympanic cavity, and meatus auditorius externus, which
would form a. canal of communication between the pharynx
and the external surface but for the interposition of the
delicate membrana tympani.

Some of the changes which take place in the cranium
while advancing from youth to maturity have already been
noticed ; but it will be well, before proceeding to describe
the modifications of the Mammalian skull, to mention certain
others which take place, to a greater or less degree, in all
skulls.

These depend mainly on the fact that the brain, and con-
sequently the cavity which contains it, and also the sense
capsules, increase in size in a much smaller ratio than the
external parts of the head, especially the jaws and pro-
minences for the attachment of muscles. The dispropor-
tionate growth and alteration of form of these parts,
concomitant with little or no change in the brain-case, is
effected partly by increase in thickness of the bones, but
mainly by the expansion of their walls and the develop-
ment of cells within, which greatly extend the outer surface
without adding to the weight of the bone.

In the Dog these cells are developed chiefly in the fore-
part of the frontal bones, constituting the frontal sinuses,
and in the presphenoid, constituting the sphenoidal sinuses.
Air passes freely into them from the nasal passages. In
many animals they attain a much larger extent than in the
Dog, reaching their maximum in the Elephant (see Fig. 64,
p. 205), where the alteration of the external form of skull
during growth, without material change in the shape or size

ix ] DEVELOPMENT. 149

of the cerebral cavity, is strikingly shown. At the same
time the alveolar borders of the jaws gradually enlarge to
adapt themselves to the increased size of the permanent
teeth which they have to support, and the various ridges and
tuberosities for the attachment of muscles become more
prominent

During these changes a gradual consolidation takes place
in the structure of the skull generally, by the partial or com-
plete union of certain of the bones by synostosis. The
union of the different bones generally proceeds in a certain
definite order, which, however, varies much in different
species. Sometimes it extends so far as to lead to complete
obliteration of all the cranial sutures.

CHAPTER X.

THE SKULL IN THE ORDKR PRIMATES, CARNIVORA,
INSECTIVORA, CHIROPTERA, AND RODENTIA.

Order PRIMATES. Man. — On comparing a longitudinal
and vertical section of a young human skull in which most
of the sutures are still distinctly seen (Fig. 53), with that of
the Dog, it will be seen to be composed of the same bones,
having very nearly the same connections, and yet the whole
form is greatly modified. This modification is mainly due
to the immense expansion of the upper part of the middle
or cerebral fossa of the brain cavity, which not only carries
the roof of the cavity a great distance from the basicranial
axis, but also forces, as it were, the anterior and posterior
walls from the vertical nearly to the horizontal position, so
that they are, roughly speaking, in the same line with the
short basicranial axis, instead of being perpendicular to it.
In addition to this great difference, the facial portion of the
skull is deeper from above downwards, and very much
shorter from before backwards.

Taking a survey of the human skull in the same order
as was done with that of the Dog, we find the craniofacial
axis, composed of the basioccipital bone (BO\ terminating
at the anterior border of the foramen magnum (/;;/) behind,

CHAP. X.]

THE SKULL OF MAN.

•;

FIG. 53. — Vertical, longitudinal, median section of a young human skull, with the first
dentition. J. As in the other sections of a skull figured, the mandible is displaced
downwards, so as to show its entire form. PMx premaxilla ; MT maxillo-
turbinal ; KT ethmo-turbinal ; .I/A" ossified portion of the mesethmoid ; Na nasal ;
eg crista galli of the mesethmoid; OS prbttosphenoid. or lesser wing of the
sphenoid ; AS alisphenoid. or greater wing of the sphenoid ; /•> frontal ; /'a
parietal ; SO supraoccipital ; M inastoid portion of the periotic ; Sy squamosal;
Per petrous portion of the periotic : the large foramen below the end of the line
is the internal auditory meatus. the small depression above it is the nearly-
obliterated floccular fossa. E.\O exoccipital, the line points to the condylar fora-
men \ _fm foramen magnum ; HO basioccipital ; BS basisphenoid ; it sella turcica ;
/'.V presphenoid. aiikylosed with the basisphenoid, forming the " body of the
sphenoid ;" /'/ pterygoid ; PI palatine ; Vo vomer ; MX maxilla ; i symphysis of
mandible ; cp coronoid process ; cd articular condyle ; a angle ; ih stylohyal, or
'• styloid process of temporal;" ch ceratohyal, or lesser cornu of hyoid ; bk
basihyal, or body of hyoid ; tk thyrohyal, or greater cornu of hyoid.

152 THE SKULL. [CHAP.

and in this young skull still separated from the basisphenoid
in front by a vertical fissure. The basisphenoid (BS} is short
and deep, and has a strongly marked pituitary fossa or " sella
turcica" (sf) above. It has completely united with the pre-
sphenoid (PS), though at birth the line of separation (below
the spot called the olivary process or tubercuhim se/lce) is still
visible. In adult age large air-cells fill the interior of this con-
joined bone, which is the "body" of the so-called "sphenoid "
of human anatomy. Anteriorly the presphenoid narrows to
a sharp vertical edge, which is in contact with the mesethmoid
(ME) above and the vomer ( Vo) below. The whole of the
upper part of the mesethmoid is ossified in the specimen
described, constituting the "lamina perpendicularis," but the
anterior and lower part forms the septal cartilage of the nose.
Its upper border forms a strong compressed triangular pro-
jection into the cranial cavity, called the " crista galli " (eg).
The posterior segment of the brain-case is completed, as
in the Dog, by the pair of exoccipitals (ExO), and a large
supraoccipital (SO).1 The triangular upper part of the latter
may be considered to represent the interparietal, though it
very soon becomes incorporated with the rest of the supra-
occipital. The middle segment is completed by large ali-
sphenoids (AS), the "greater wings of the sphenoid bone,"
and enormously extended, somewhat square- shaped parietals
(Pa) ; the frontal segment by narrow triangular orbito-
sphenoids (OS), the " lesser wings of the sphenoid bone,"2
and by large arched frontals (Fr).

1 The "occipital bone" of human anatomy is formed by the coales-
cence of the basioccipital, exoccipitals, and supraoccipital.

2 The "sphenoid bone" of human anatomy is formed by the union
of the basisphenoid, presphenoid, alisphenoids, orbitosphenoids, and
the pterygoids. The basal portion ultimately ankyloses with the
occipital.

x.] MAN. 153

Of the fossae into which the cranial cavity is divided, the
olfactory fossa is very small, rather narrow, elongated, and
shallow. The cribriform plate which closes it in front, in-
stead of being vertical as in the Dog, is horizontal, and
almost in the same line with the basicranial axis. It is
bounded in the median line, and separated from the cor-
responding fossa of the other side by the prominent crista
galli of the mesethmoid. The middle fossa is, as before
said, of comparatively enormous extent ; it is bounded pos-
teriorly by the tentorial ridge, having the same relations to
bones as in the Dog, but lying more horizontally and being
far less prominent, having no osseous shelf like inward exten-
sion. This fossa is distinctly divided into an anterior and
posterior portion, by the strongly projecting hinder ridge of
the orbitosphenoid The floor of the anterior portion is
arched in consequence of the inward projection of the roof
of the orbit, while the floor of the posterior or " temporal
fossa " is deeply concave. The cerebellar fossa is of mode-
rate si/e, and lies entirely underneath the hinder part of
the cerebral fossa.

The "sclla turcica," or depression in the basisphenoid for
the lodgment of the pituitary body of the brain, is bounded
posteriorly by an elevated transverse ridge, the corners of
which are called the " posterior clinoid processes." Cor-
responding processes projecting backwards from the orbito-
sphenoids are called " anterior clinoid processes."

The foramina in the base of the skull scarcely differ from
those of the Dog. i. The olfactory has been already
described. 2. The optic is a large round hole close to the
inner and posterior part of the orbitosphenoid. 3. The
sphenoidal fissure is larger than in the Dog. and produced
externally into a long narrow slit. 4 and 5. The foramen
rotundum and the foramen ovale pierce the alisphenoid, one

154 THE SKULL. [CHAP.

near its anterior, the other near its posterior border. Close
behind the last named is a small hole (" foramen spinosum "),
through which a branch of the external carotid artery
(middle meningeal) enters the brain-cavity. 6 and 8. The
foramen lacerum medium basis cranii and the foramen
lacerum posterius have the same functions and relation as
in the Dog. 7. Between these two the periotic has the
conspicuous meatus auditorius internus on its inner side-
The depression above this, for the lodgment of the floc-
culus, is distinctly seen in fcetal human skulls up to the
time of birth, but it afterwards becomes gradually oblite-
rated. 9. The condylar foramen perforates the exoccipital,
as in the Dog; and lastly (10), the foramen magnum has
the same general subcircular form, and is bounded by the
same bones, but differs greatly in direction, its plane looking
mainly downwards instead of backwards.

The nasal cavities differ chiefly from those of the Dog in
their shortness and greater vertical height. In their inner
wall, the descending median plate of the vomer ( Vo) is
much more developed. The pterygoids (Pi) are extended
vertically, are narrow from before backwards, end below in
a marked " hamular " process, and soon ankylose with the
pterygoid plates of the alisphenoid anteriorly, but posteriorly
are separated from them by a well-marked " pterygoid
fossa." l The palatines (PI) and maxillae (Mx) are short
from before backwards. The premaxillae (PMx) are small
and early ankylosed with the maxillre.2 The nasals (Net)

1 The pterygoid, not being recognised as a distinct bone, is commonly
described in works on human anatomy as " the internal pteryrroid plate
of the sphenoid ; " the pterygoid process of the alisphenoid being the
"external pterygoid plate."

2 The premaxilla is a distinct bone in the human foetus, but is covered
on its external or facial aspect by a process of the maxilla, which extends
over it towards the middle line, and becomes completely fused with it

x.] MAN. 155

are short and nearly vertical, broad below and narrow
above. The anterior nares are also nearly vertical. The
turbinal bones are comparatively little developed, and of
simple structure, especially the lower or maxillo-turbinal
(MT). The flat bony plate on the outer side of the ethmo-
turbinal or " os planum," instead of lying against the inner
side of the maxilla, forms part of the outer wall of the nasal
cavity and inner wall of the orbit, uniting with the frontal
above, the lacrymal in front, the maxilla below, and the
palatine behind.

The group of bones placed around the organ of hearing,
periotic, squamosal, and tympanic, though originally dis-
tinct, become united together soon after birth to form the
so-called "temporal bone." They differ from the corre-
sponding bones in the Dog in the following particulars. The
periotic has a very much larger mastoid portion (J/), which
forms a considerable part of the wall of the cerebellar fossa.
In the new-born infant its outer surface is smooth and flat,
but as life advances, air-cells become developed within it,
communicating with the tympanic cavity, and a strongly-
marked descending projection, the " mastoid process,"
appears on the lower and anterior part of its outer surface.
The squamosal (Sq) is a large flat vertical plate, forming a
considerable part of the wall of the posterior cerebral fossa,
behind the alisphenoid. Its zygomatic process is com-
paratively slender and straight The tympanic forms a
long tubular external auditory meatus, but its inner part

before birth, so that no trace of the maxillo-premaxillary suture is ever
seen on the outer side of the face. On the inner and palatal aspect of
the bones the suture is always evident at birth, and can often be traced
even in adult skulls. See G. IV. Callender " On the Formation and
Early Growth of the Bones of the Human Face." (Phil. Trans. 1869,
p. 163.) Also : P. Albrecht, " Sur la fente maxillaire et les os inter-
maxillaires," etc. 1883.

156 THE SKULL. [CHAP.

joins the periotic, forming the floor of the tympanic cavity
without being inflated into an auditory bulla. Its under
surface is produced into a rough ridge, to the inner side of
which the large carotid canal perforates the base of the
periotic, being directed obliquely forwards and inwards.
In adult skulls the stylohyal often becomes ankylosed with
the tympanic and periotic, constituting the " styloid process
of the temporal bone."

In examining the external aspect of the skull, the large
smooth subglobular or oval brain-case, constituting by far the
larger part of the whole cranium, is strikingly different from
that of the Dog. The occipital surface, instead of being
vertical, is nearly horizontal. The condyles, instead of
being at the hindermost part of the skull, are not far from
the middle of the base. The paroccipital processes of the
exoccipitals are represented by mere rudiments, the so-called
"jugular eminences"; on the other hand as before men-
tioned, the mastoid processes, almost obsolete in the Dog,
are very greatly developed. The occipital crest is repre-
sented by a slightly raised and roughened line, the " superior
curved line," and the sagittal crest is absent.

The sutures connecting the bones of the upper surface
of the cranium are remarkable for their wavy or indented
character, processes from one bone interlocking with those
from the other in a most complex manner, at least on the
external surface, for seen from within they appear com-
paratively straight and simple. There are very often
irregular ossifications, separated from the contiguous bones,
lying among the indentations of the occipito-parietal suture,
called "Wormian bones."1 The temporal fossa? are but

1 In works on human anatomy, the occipito-parietal suture is com-
monly called " lambdoid ; " the interparietal, "sagittal;" and the
front j- parietal, " coronal."

x.] MAN. 157

indistinctly marked out by a curved line above, and are
separated from each other by a wide expanse formed by
the smooth rounded upper part of the parietal and frontal
bones. The orbit is completely encircled by bone, the
outer margin being formed by a process from the malar
ascending to join the post orbital process of the frontal ; and
it is, moreover, in great part sepaiated from the temporal
fossa by an extension inwards of the ascending process of
the malar meeting the alisphenoid, although a communica-
tion is left between the two cavities below in the " spheno-
maxillary fissure." The axis of the orbital cavity is directed
more forwards than in the Dog. The face is altogether very
much shorter, broader, and flatter.

In the inferior surface of the skull the palate is seen
to be much shorter and wider than that of the Dog, es-
pecially anteriorly, where its outline forms an almost semi-
circular curve. The maxillo-palatine suture is nearly
straight transversely, and so is the hinder border of the
palate, though produced backwards into an obtuse spine at
the middle line. The distance between the hinder border
of the palate and the foramen magnum is much shorter
relatively, the space between the pterygoids being particularly
short and wide. The true pterygoids and pterygoid plates
of the alisphenoid are widely separated posteriorly, leaving
a considerable fossa between them ; and the latter are larger
and project further backwards than the former. The under
surface of the tympano-periotic region is rough and irregular,
instead of being smooth and bullate, and the perforation
for the internal carotid artery is very conspicuous. There
is no alisphenoid canal, scarcely any postglenoid process, no
distinct glenoid venous foramen, a very small paroccipital,
and a very large mastoid process. By the inclination of the
occipital surface downwards, instead of backwards, an inferior

158 THE SKULL. [CHAP.

view of the skull includes nearly all this surface, with the
large foramen magnum and the condyles.

In accordance with the general form of the face the
mandible is short. The two rami of which it is originally
formed unite together at the symphysis within a year after
birth. They are widely divergent behind, and approach in
front at a much more obtuse angle than in the Dog. The
horizontal portion of each ramus is deep and compressed,
the lower margin straight or slightly concave, and produced
anteriorly rather in front of the alveolar margin so as to
occasion the mental prominence characteristic of the human
lower jaw. The anterior symphysial margin (Fig. 53, s),
therefore, instead of sloping upwards from behind forwards,
is vertical, or rather inclined in the other direction. Pos-
teriorly, the condyle (cd) is more elevated than in the Dog
and is less transversely extended. The coronoid process
(cp) is smaller and less recurved. The posterior border,
between the condyle and the angle (a\ is nearly straight
and vertical, and the angle is rounded, compressed, slightly
everted, and not produced into any hook-like process, as in
the Dog. The depression for the masseter muscle is very
faintly marked.

The hyoidean apparatus differs in several particulars from
that of the Dog. The tympanohyal can generally be
recognised in the skull of an infant at birth and for a few
years after, as a cylindrical piece of bone, with a truncated
lower extremity, about one-twentieth of an inch in diameter,
seated in a depression in the hinder border of the tympanic
immediately to the anterior and inner side of the stylo-
mastoid foramen. Its upper end becomes soon ankylosed
with the periotic. The tympanic is produced around it
anteriorly, constituting the " vaginal process." The stylohyal
(s/i), at first a long styliform piece of cartilage, continuous

x.] MAN. 159

with the tympanohyal, commences to ossify by a separate
centre before birth, and, at a very variable period after-
wards, is often (but by no means constantly) ankylosed
with the tympanohyal and surrounding cranial bones, con-
stituting the so-called "styloid process." This is a con-
dition not met with in any other Mammal. Below the
stylohyal the greater part of the anterior hyoid arch is
represented by a slender ligament (the " stylohyoid " liga-
ment), there being no ossification corresponding to the
Dog's epihyal ; but the ceratohyal (ch) to which the liga-
ment is attached below, is a small bony nodule, the
" lesser cornu of the hyoid " of human anatomy, which
is articulated synovially to the upper corner of the
outer extremity of the basihyal, though sometimes in old
age becoming ankylosed. The basihyal (bh), or " body
of the hyoid," is transversely oblong, hollowed posteriorly,
and deeper from above downwards than in the Dog. The
thyrohyals (///) or "greater cornua of the hyoid," are elon-
gated, nearly straight and somewhat compressed. They
usually become ankylosed before middle life with the outer
extremities of the basihyal.

The remainder of the true Primates (Simii/ia, or Monkeys)
have the skull formed generally on the same plan as that
of Man, with certain modifications in detail.

The facial portion is enlarged and elongated as compared
with the cerebral potion, though to a very variable extent
in different members of the group.

In nearly all, the brain-cavity maintains the same general
form as in Man, though it is usually of less comparative
vertical extent. With few exceptions, the middle compart-
ment for the lodgment of the cerebrum retains its
relative situation and superiority in size to the cerebellar

160 THE SKULL. [CHAP.

and the olfactory fossae, completely overlying them both ;
and consequently the occipital region of the skull with the
foramen magnum behind, and the cribriform plate of the
ethmoid in front, are in the same general horizontal line
with the basicranial axis as in Man, and not perpendicular
to them as in the Dog.

It is remarkable that the deviations from this general rule,
especially as regards the plane of the occipital surface, are
not in relation to the general position of the animals in a
descending series, from Man to the lowest Monkeys ; for the
occipital surface is nearly vertical in the anthropoid Gibbons
(Hylobatcs), especially // syndactylus (the Siamang), and
completely so in the American Howling Monkeys (Mycetes),
where the cerebral fossa does not project in the least degree
behind the cerebellar fossa; while in the Baboons (Cyno-
cephalus], among the Old World Monkeys, and still more
in some of the smaller forms of American Monkeys
(as Saimiris], the posterior development of the cerebral
fossa is so great as to throw the supraoccipital bone con-
siderably more into the posteriorly prolonged base of the
skull even than in man.

The olfactory fossa is always small. It is not only very
short, but, in consequence of the considerable projection
inwards of the portion of the frontal forming the roof of the
orbit on each side of it, is both narrow from side to side,
and deep from above downwards.

In most of the Siwiina, including the Gorilla and Chim-
panzee, the frontals meet along the middle line over the
presphenoid, between the mesethmoid in front and thr
orbitosphenoids behind ; but the Orang agrees with Man in
wanting this postethmoid union of the frontals, and so also
do some of the Cebidce.

The fossa on the inner surface of the periotic for the

x.] PRIMATES. 161

floccular process of the cetebellum is almost obliterated in
the adult Gorilla, Chimpanzee, Orang, and Gibbon, but is
persistent and often very large in all other Monkeys.

A partial ossification of the tentorium from the inner
edge of the periotic takes place in some of the American
Monkeys, as Mycdes and Cebns.

The suture between the basisphenoid and the presphenoid
remains distinct in the Baboons and all the lower Monkeys,
until the animal has nearly attained its full size and acquired
its permanent teeth ; but it is completely obliterated, and
the cancellous structure of the two bones is continuous, in
the Gorilla, Chimpanzee, and Orang, while the animal still
retains all its milk-teeth.

The nasal cavities, with their surrounding bones, are
generally longer and of less vertical extent than in Man,
but, as in the case of the inclination of the occipital plane,
not following any regular serial descent. Thus the propor-
tions of these parts are more like those of Man in many
of the smaller American Ccbidie than in the long-faced or
" Dog-headed" Baboons (Cynocefhali} of the Old World.

The vomer is generally longer, and of less vertical extent
than in Man. The turbinals have much the same general
characters, their relative situation of course varying with
the elongation, or otherwise, of the nasal passages. The os
planum of the ethmoturbinals always forms part of the
inner wall of the orbit, having the same relations as in
Man.

The pterygoid plate of the alisphenoid is usually largely
developed, and generally projects considerably backwards
beyond the pterygoid bone (which is narrow, and has a very
distinct hamular process), and there is always a wide and
deep fossa between them.

The premaxilla is ahvays distinct on the facial surface,

162 THE SKULL. [CHAP.

and the suture between it and the maxilla is only obliterated
in aged specimens. It generally extends upwards on the
side of the anterior nares, so far as to meet the nasal and
completely exclude the maxilla from taking any part in the
boundary of this opening.

The lacrymal foramen is never situated externally to the
orbit, although, in the lower forms, it may be close upon
the margin.

As in Man the postorbital process of the frontal meets
the orbital process of the malar so as completely to encircle
the outer side of the orbit ; and an extension backwards and
inwards of these bones joining the alisphenoid divides the
orbit from the temporal fossa.

The nasal bones vary much in length and breadth, but
they present the peculiarity throughout the order of a great
tendency to ankylose together in the middle line, even at a
comparatively early age.

In all the smaller and middle-sized Monkeys the general
surface of the calvaria is oval and smooth, but in the larger
Baboons and Orangs there are well-marked supraorbital,
sagittal, and occipital ridges. These attain their greatest
development in the adult male Gorilla, where they com-
pletely mask the original form of the cranium. Their size,
in this sex, appears to increase with age ; while in the
oldest females, on the other hand, they are but slightly
apparent.

The paroccipital process is always rudimentary, as in
Man.

The squamosal in the higher forms is developed much as
in Man ; but in the lower forms it is more reduced, and
takes a smaller share in the formation of the side wall of
the cranium. It generally comes in contact, at its upper
anterior angle, with the frontal, but not in the Orang or in

x.] PRIMATES. 163

the Cebida, in which animals the union of the parietal and
the alisphenoid separates the frontal from the squamosal, as
is usually the case with Man. The glenoid surface is
flatter than in Man, and there is a well-marked postglenoid
process.

In the PlatyrrhincK) with the individual exception of
certain Afycetcs and Aides, the parietal and malar bones are
in contact with each other, separating the frontal from the
alisphenoid on the side wall of the skull. In the Catar-
r/rituc the reverse takes place, the alisphenoid and frontal
bones meeting each other and separating the malar from
the parietal. Another point of difference between the Old
and New World Monkeys is that in the latter is a small
slit in the malar wing not far from the point where the
malar, parietal and alisphenoid bones meet. This slit,
together with the infraorbito-temporal foramen, is the last
remnant of a wide orbito-temporal foramen.

The zygoma is usually narrow, horizontal, and slightly
arched outwards.

The periotic generally resembles that of Man, and the
mastoid portion is conspicious on the outer side of the
skull between the squamosal and the exoccipital ; but its
surface is smooth and rounded, without any distinct mas-
toid process.

In all the Old World species, the tympanic forms an elon-
gated inferior wall to the external auditory meatus, which
has consequently a considerable bony tube ; but in all the
American Monkeys this bone retains more or less its primi-
tive annular condition, and the cavity of the tympanum is
close to the external wall of the cranium. This character
alone will readily serve to determine to which of the two
great divisions of Monkeys a skull may belong.

No auditory bulla is developed in any of the Old World

M 2

164 THE SKULL. [CHAP.

Monkeys, but in all the Cebidx and Hapalidtz the inferior
surface of the ankylosed periotic and tympanic is somewhat
inflated.

The carotid canal is always very conspicuous, entering
the under surface of the periotic near its hinder border.
There is often a glenoid foramen, but never an alisphenoid
canal.

The foramen rotundum perforates the alisphenoid, but
the foramen ovale is usually a notch on its posterior border,
completed by the periotic behind.

The mandible presents the same general characters as
that of Man, but the horizontal portion of the ramus
is usually more elongated, and the anterior border slopes
upwards and forwards, there being a complete absence of
mental protuberance. The condyle is extended trans-
versely, the coronoid process well developed and recurved.
The posterior or ascending portion of the ramus is broad
and flat ; the angle well developed, square, or more or
less rounded, but without any special pointed process as in
the Dog.

In the Howling Monkeys (Mycetes) the hinder or ascend-
ing portion of the ramus is remarkable for its extent both
vertically and an tero- posteriorly, corresponding to a certain
extent with the extraordinary development of the vocal
organs, which it partially covers and protects.

The Sim Una are remarkable in never, or very rarely,
having an ossified stylohyal ; but on looking closely at the
base of the periotic, immediately to the anterior and inner
side of the stylomastoid foramen, a very small depression,
in which there is sometimes a minute ossified tympano-hyal,
can generally be seen. To this the ligament representing
the stylohyal is attached.

In very few of the Old World Monkeys is there any

X.]

PRIMATES.

165

ossification in the anterior hyoid arch (see Fig. 54) ; but in
some Cercopitheci a short, bony, cerato-hyal is found. This
occurs also in the American Monkeys (Fig. 55), with occa-
sionally the addition of a second piece (epihyal).

The thyrohyals are always well-developed, long, narrow,
nearly straight, and somewhat flattened.

The basihyal varies much in form. In the anthropoid Apes
it is broad transversely ; but in nearly all the other Monkeys
its antero-posterior extent exceeds its breadth, owing to a
great development from the posterior border. It is generally
convex below, and concave above and behind, forming a

FlG. 54. — Inferior surface of hyoid boots
of Baboon (CyniKepkalm pamirim,),
bh basihyal ; th thyrohyal.

FIG. 55. — Inferior surface of hyoid bones
of an American Monkey (Lago'hruc
humbolJtii). tk thyrohyal ; c h cerato-
hyal ; ck epihyal.

considerable cavity in which the median laryngeal air-sac
is lodged. This condition is enormously exaggerated in
the American Howling Monkey (Mycetes), where the basi-
hyal is transformed into an immense subglobular, thin-
walled, bony capsule, with a large orifice posteriorly, by
which the laryngeal air-sac enters, and having the straight
narrow thyrohyals attached on each side. In this genus
there are no ossifications in the anterior arch.

While in nearly all the characters in which the skull of
Man differs from that of the Dog, the Simiina agree with

1 66 THE SKULL. [CHAP.

the former ; the Lemnrina, on the other hand, more resemble
the lower type.

In the Common Lemur the general proportions of face to
cerebral cavity, and the inclination of the occipital and
olfactory planes of the cranium, are quite dog-like. The
orbits, although completely surrounded behind by the
junction of the postorbital processes of the frontal and the
malar, are yet perfectly continuous with the temporal fossa
beneath this bony bar ; that extension inwards of the
frontal and malar to meet the alisphenoid, and thus form a
posterior external wall of the orbit, so characteristic ol
Man and all Monkeys, being absent. The lacrymal fora-
men, situated on the facial part of the bone, is altogether
external to the margin of the orbit. The os planum of
the ethmo-turbinal does not enter into the inner wall of the
orbit, but is shut out from it by the maxilla, as in most
inferior Mammals. The inferior surface of the tympanic is
developed into a large rounded bulla. The hyoid apparatus
much resembles that of the Dog, having the stylohyal,
epihyal, and ceratohyal all distinctly ossified in the anterior
arch, and the basihyal in the form of a narrow transverse
bar.

Some of the Lemurina have much shorter faces than the
common species, though still possessing all the essential
characters of the group. Among these, Tarsius is remark-
able for the extraordinary size of the orbits, which are so
expanded that their margins form prominent, thin, bony
rings, and the interorbital part of the skull is reduced to an
exceedingly delicate septum. The orbit is also partially
separated from the temporal fossa as in the Simiina.

The general characteristics of the skull of the CARNIVORA
have been described, as seen in the Dog. The more

X.] CARNIVORA. 167

obvious modifications from this type relate to the compara-
tive length and compression or width of the facial portion,
the strength and curve of the xygomatic arch, and the extent
to which the various ridges and processes for the attachment
of muscles are developed. Thus the Cats have short and
round skulls, with wide zygomatic arches ; and in the Bears
(especially the Polar Bear, Ursus maritimus) the whole
skull is elongated, and the nasal cavities are greatly enlarged
as compared with the brain-case, and the maxillo-turbinal
bones are correspondingly developed.

But there are certain other modifications of the cranial
bones, which, being less obviously adaptive to functional
purposes, and being constantly associated with structural
modifications in other parts of the body, are of considerable
value in classifying the members of the group. Of these
the most important are related to the form and structure of
the auditory bulla, and the surrounding parts of the base of
the cranium.

In the Bears, the auditory bulla is comparatively little
inflated. It consists of a single bone (tympanic), readily
detached from the cranium in skulls of young animals. Its
form is more or less triangular, being broad and nearly
straight at the inner edge, and produced outwards into a
considerably elongated floor of the external auditory meatus.
Its greatest prominence is along the inner border; from
this it gradually slopes away towards the meatus. The
entrance of the carolid canal is a considerable circular
foramen, near the hinder part of the inner edge of the bulla.
In old animals it is partly concealed by the prominent lip of
the basioccipital, which abuts against the inner edge of the
bulla ; and by the growth of this, and the paroccipital pro-
cess, it becomes almost included in the deep fossa leading
to the foramen lacerum posterius. When a section is made

1 68

THE SKULL.

[CHAP.

through the auditory bulla (see Fig. 56) it is seen to be a
simple thin-walled bony capsule, imperfect above, where it
fits on to the petrosal and squamosal bones, and prolonged
externally into the much thickened spout-like floor of the
meatus externus. At the inner extremity of this floor is a
freely projecting oval lip (/), which gives attachment to the
membrana tympani, and which is the original and first ossified
ring-like portion of the tympanic bone. In the front of the

Cut'

FIG. 56. — Section of the left auditory bulla and surrounding bones of a Bear (Ursns
fcrox). Si/ squamosal; T umpanic; BO basioccipital ; am external auditory
meatus ; t tympanic ring ; c Eustachian canal ; Car carotid canal. (From Proc.
Zool. Soc. 1869.)

floor of the bulla is the groove for the Eustachian canal (e) :
between this and the inferior part of the tympanic ring, a
low and thin ridge of bone with a concave free margin rises
from the floor of the cavity. This is the only indication of
any septum or division of the cavity of the bulla.

Behind the bulla, the prominent and tuberous paroccipital
process projects downwards, outwards and backwards, stand-

x.] CARNIVORA. 169

ing quite ofl from the bulla, and only connected with it by a
low laterally compressed ridge. Between the paroccipital
process and the occipital condyle is a smooth concave surface
the front of which is excavated into a deep notch, the
posterior boundary of the foramen lacerum posterius,
between which and the condyle is situated the condylar
foramen, which transmits the hypoglossal nerve. At the
outside of the bulla, just behind the external auditory
mcatus, the mastoid process is distinct and prominent, and
widely separated from the paroccipital. There is a very
conspicuous glenoid foramen situated just behind the post
glenoid process of the squamosal.

All the Ursidtf, Procyonida, and Mustelida agree with
the true Bears in the general characters of this region of the
skull ; for even when (as in some of the smaller species) the
auditory bulla is considerably dilated, it always has its
greatest prominence near the middle of the inner border, and
gradually slopes away from this point to a prolonged floor of
the auditory meatus ; and though there are often trabecula;
or partial septa passing mostly transversely across the lower
part,1 there is no distinct and definite septum dividing it
into a separate outer and inner chamber. In all cases, on
looking into the external auditory meatus (in the dried
skull when the membrana tympani is removed) the oppo-
site wall of the bulla can be seen ; or if a probe is passed
into the meatus, no obstacle will prevent its touching the
inner wall.

In the Tiger, which may be taken as a type of the Felidce,
the auditory bulla is very prominent, rounded and smooth
on the surface, rather longer from before backwards than
transversely, its greatest prominence being rather to the

1 Especially developed in the Weasels (Mustela], in which also the
entire parieties of the bulla are thickened and cancellous.

170

THE SKULL.

[CHAP.

inner side of the centre. The lower lip of the external
auditory meatus is extremely short ; the meatus , in fact,
looks like a large hole opening directly into the side of the
bulla. On looking into this hole, at a very short distance
(just beyond the tympanic ring), a wall of bone is seen quite
impeding the view, or the passage of any instrument, into
the greater part of the bulla. In the section (Fig. 57) it will
be seen that this wall is a septum (s), which rises from the

f the left auditory bulla of the Tiger (t'rlis tieris).

mosal ; t't penotic ; />'(' basioccipital ; am external auditory meatus ;

chamber ; ic the inner chamber : s th

plum ; * the aperture of communication

between the chambers, (from JJroc. Zool. Soc. 1869.)

floor of the bulla along its outer side, and divides it almost
completely into two distinct chambers ; one (cv), outer and
anterior, is the true tympanic chamber, and contains the
tympanic membrane and ossicula, and has at its anterior
extremity the opening of the Eustachian tube (<>) ; while the
other (/>), internal and posterior, is a simple but much
larger cavity, having no aperture except a long but very
narrow fissure (*) left between the hinder part of the top of

x.] CARNIVORA. 171

the septum and the promontory of the periotic, which
fissure expands posteriorly, or rather at its outer end, into a
triangular space, placed just over the fenestra rotunda, so
that the opening of this fenestra is partly in the outer and
partly in the inner chamber of the bulla. This chamber is
formed by a simple capsule of very thin but dense bone.-
deficient only at a small oval space in the roof, where the
periotic projects into and fills up the gap, except such
portion of it as is left to form the aperture of communica-
tion with the outer chamber.

Not only are these two chambers thus distinct, but they
are originally developed in a totally different manner. At
birth the only ossification in the whole structure is the in-
complete ring of bone supporting the membrana tympani,
and developed originally in fibrous tissue. Ossification
extends from this, so as to complete the outer chamber,
and the very limited lip of the meatus auditorius externus.
The inner chamber is formed from a distinct piece of hya-
line cartilage, which at birth is a narrow slip, pointed at
each end, lying between the tympanic ring and the basi-
occipital, applied closely to the surface of the already
ossified periotic, and forming no distinct prominence on the
under surface of the skull. Soon after birth this increases
in size, and gradually assumes the bullate form of the wall
of the inner chamber. In young animals, even some time
after the ossification of the bulla is complete, the distinc-
tion between the two parts is clearly seen externally ; not
only are they marked off by a groove, but the tympanic
portion has a more opaque appearance than the other. The
septum is formed by an inversion of the walls of both ap-
plied together, and ultimately perfectly fused in Felts, although
remaining permanently distinct in some of the Virerrida.

The carotid foramen in the TigQr is only represented by

172 THE SKULL. [CHAP.

a minute groove deep in the recess of the foramen lacerum
posterius. In the smaller Cats, this groove is more super-
ficial, but always very minute, and apparently never converted
into an actual foramen, except by the contiguous wall of the
basioccipital.

The paroccipital process is flattened over the back of the
bulla, being applied closely to the whole of its prominent
rounded hinder end, and projecting, as a rough tubercle,
slightly beyond it. From the inner side of this process a
sharp ridge runs towards the occipital condyle. This forms
the posterior boundary of a deep fossa, at the bottom of
which is the foramen lacerum posterius, and in the hinder
part of which, under cover of the aforesaid ridge, the
condylar foramen "opens. The mastoid process is a
moderately conspicuous rough projection, not very widely
separated from the paroccipital. There is no distinct
glenoid foramen.

The Viver rider, agree with the Felidce in having the auditory
bulla divided into two cavities by a bony partition, in having
the paroccipital spread over the hinder surface of the bulla,
and in having no prolonged external auditory meatus ; but
the bulla is more elongated and compressed, and the inner
chamber is placed altogether behind the outer or true
tympanic chamber.

In the Hy?ena this region of the skull much resembles the
same part in the Cats, but the bulla is simple and undivided.
In the Dogs there is a partial septum, and otherwise the
characters are intermediate between the two extremes of the
Bears on one side, and the Cats on the other.1

1 For the various modifications of the structure of this part of the
skull in the different genera of the order, see "On the Value of the
Characters of the Base of the Cranium in the Classification of the Order
Carnivora." (Proc. Zool. Soc. 1869, p. 5.)

x.] CARNIVORA. 173

In nearly all the Carnivora the hyoidean apparatus is con-
structed on the same plan as described in the Dog, having a
narrow, transversely elongated, curved basihyal, either round
or compressed from above downwards, a nearly straight
compressed thyrohyal, not ankylosed with the basihyal, and
a well-ossified anterior cornu, composed of three distinct
pieces of subequal length. In the Lion, Tiger, and Leopard,
however, the anterior arch is imperfectly ossified, the dif-
ferent bones being small, and connected together by long
ligamentous intervals ; but in the Puma, Cheetah, Lynx, and
Cat, the bones are large, and in close relation with each
other.

In the Seals the brain-cavity is very broad, round, and
rather depressed. The orbits are large, and the interorbital
portion of the skull greatly compressed. The olfactory
chambers of the nasal cavities are consequently very narrow,
and the ethmo-turbinals little developed ; but in front of the
orbits the cavities widen, and the maxillo-turbinals are very
large and complex. The mesethmoid is of considerable
vertical extent, and its ossified portion, which is extensive,
terminates anteriorly in a straight vertical line. In some
forms, as Cystflp/tora, this ossification extends in front of the
nasals. The hyoid resembles that of the typical Carnivora,
all the elements being well ossified and distinct. The
Otariidir, or Eared Seals, also called Sea Bears or Sea
Lions, are intermediate in most of their cranial characters
between the true Seals and the Bears.

The skulls of the animals composing the Order INSEC-
TIVORA present great variations.

In some of the higher forms, as Galeopithccus, Tupaia,
Macroscelides, and Rhynchocyon, the cranium much resembles
that of the Ltmurina, having a considerable and vaulted

1 74 THE SKULL. [CHAP.

cerebral cavity, large orbits, nearly vertical occipital plane,
large olfactory fossre, a well-developed zygoma tic arch
sending up a postorbital process to meet a corresponding
one from the frontal so as either partially or completely to
encircle the orbit behind, and tympanics ankylosed with
the other cranial bones, dilated into a bulla, and pro-
duced externally into a tubular auditory meatus. The
face is generally elongated, and narrow anteriorly, but in
Galcopithccus it is broad and depressed.

In the Macroscelidce, or Elephant Shrews, the auditory
meatus is very large, the tympanic bulla much inflated, and
there are sometimes also very large mastoid bulla:.

In Tupaia, the malar has a large, oval, longitudinal per-
foration. There are also in this genus, as in some of the
other Insectivora, vacuities in the palate, arising from defects
of ossification, like those found in many Marsupials.

In the remaining Insectivora the cranial cavity is of small
relative size. The orbit and temporal fossa are completely
continuous, and there is often not even a trace of a post-
orbital process to the frontal or malar.

In the Erinaceidce (Hedgehogs) and the Ccntetida' the
tympanic is a mere ring unankylosed to the surrounding
bones, but a kind of bulla is formed by a lamella pro-
jecting from the basisphenoid to join its inner and inferior
edge.

In Erinaccns and Gymmtra the zygomatic arch is com-
plete, but slender, and formed chiefly by the processes of the
maxilla and squamosal, "which meet each other, the malar
being a small splint-like bone attached to the outer and
under side of the middle of the arch. In the Ccntetidtc the
malar is entirely absent, and, as the zygomatic processes of
both maxilla and squamosal are very short, there is no bony
arch. Centetes (the Tenrec) has a remarkably elongated

x.] INSECTIVORA. 175

and narrow skull (both cranium and face partaking of the
same character), with very prominent occipital and sagittal
crests. Both in this genus and in Erinaceus (the Hedge-
hog) the mesoptervgoid fossa at the base of the skull is
very deep, and ends posteriorly in a hemispherical depression
in the basisphenoid, between the wing-like processes which
abut against the inner wall of the tympanic. Both parocci-
pital and mastoid processes are also well developed.

The Moles (Tatyida:) have an elongated and depressed
cranium, broad posteriorly, and gradually narrowing to the
muzzle. The occiput slopes upwards and forwards, the
supraoccipital being greatly developed. The zygomatic
arches are complete, but very slender, and show no dis-
tinct malar bones. There are no postorbital or paroccipital
processes. A lamelliform expansion of the upper edge of
the periotic (pterotic, Parker) forms part of the lateral wall of
the cranium, as in the Echidna. The tympanic is united
with the other bones of the cranium to form a flattened
bulla, produced into a short meatus with a small external
opening. There is a small " prenasal " ossicle at the anterior
extremity of the mescthmoid cartilage, as in the Pig.
Myogah agrees with the Shrews in having no zygoma nor
postorbital process.

In the Cape Golden Mole (Chrysochloris) the cranium is
conical, very broad and rounded behind, and pointed in
front. There are no postorbital processes. The zygoma is
complete, and tolerably strong. The tympanics ankylose
with the skull, and form a completely ossified bulla.

In the Shrews (Soriddie) the cranium is broad behind and
tapering forwards. The facial portion is long and narrow.
The occiput slopes much forwards. There is no zygoma
and no postorbital process. The postglenoid process of the
squamosal is remarkably large. The tympanic is ring-like,

176 THE SKULL. [CHAP.

and there is a large unossified space on each side of the
base of the skull.

The mandible in the Insectivora has generally an elongated
and rather narrow horizontal portion, above which the
transversely extended condyle is but slightly elevated, and
there are well-developed coronoid and angular processes ;
the latter is remarkably long and slender in the Shrews.

The hyoid is formed generally like that of the Carnivora,
with three complete extracranial ossifications in the anterior
arch, a transversely extended basihyal, and tolerably long,
stout, flattened thyrohyals, sometimes ankylosed with the
basihyal.1

Order CHIROPTERA. — In the large Frugivorous Bats
(Pteropus), the cranium is generally elongated, the cerebral
cavity large, oval, arched above, and contracted in front :
its walls formed mainly by the greatly expanded parietals,
both supraoccipital and frontals being small. In old indi-
viduals of some species there are well-marked sagittal and
occipital crests. The base of the cranium is elongated, flat,
and thin. The facial part is long and rather compressed.
The postorbital processes of the frontals are long and
pointed, and partially define the orbits behind ; but there
is usually no corresponding ascending process from the
zygomatic arch, which is long and slender, and mainly
formed by the processes of the maxillary and squamosal,
the malar being a splint-like bone attached to their under
and outer surface. The lacrymal foramen is situated outside
the margin of the orbit. The nasals are long and narrow,
and often ankylose together in the middle line. The pre-
maxillse are small. The palate is elongated backwards :

1 For details of the osteology of the Insectivora, see G. E. Dobson's
valuable monograph of the group, now in course of publication.

x.] CHIROPTERA. 177

the horizontal plates of the palate bones being large and
early united in the middle line, without defects of ossifica-
tion. The pterygoids are small. There is no alisphenoid
canal. The glenoid fossa is broad and shallow ; the post-
glenoid process very little developed, and with a venous
foramen behind it. The tympanics are very slightly con-
nected with the neighbouring bones, and are consequently
nearly always lost in macerated skulls. A wedge-shaped
portion of the mastoid appears on the outside of the skull
between the squamosal and the exoccipital. The par-
occipital process is long and rather slender and directed
downwards and backwards. The periotic has a large and
deep fossa for the flocculus on its inner side.

FIG. 58. — Hyoid bones of Frugivorous Rat (Ptervfus) from below. M bosihyal ;
ty thyrohyal ; sh stylohyaL

The mandible has a high, broad, recurved coronoid pro-
cess, a transversely extended condyle, and a flattened rounded
angle, without a distinct process.

The hyoid (Fig. 58) has a narrow, transversely extended
basihyal, with which the elongated, laterally compressed and
curved thyrohyals are commonly ankylosed. The anterior
cornu contains three slender ossifications of nearly equal
length.

The Insectivorous Bats generally have the skull shorter
and broader than the Pteropi. The cranial cavity in many
species is almost globular, with thin smooth walls, though
sometimes sagittal and occipital crests are developed. The
occipital foramen is very large. The zygoma is slender.
Postorbital processes are sometimes well developed, but

178 THE SKULL, [CHAP.

more often small and rudimentary. The face is usually
short and broad, in some (as Mojinops] bent upwards on the
cranium in a remarkable manner, so that the plane of the
palate is nearly perpendicular to the basicranial axis. The
premaxilke are generally small, sometimes not meeting in
the middle line, and sometimes (as in Megaderma) altogether
wanting. The tympanics are annular, not ankylosed to the
surrounding bones, nor prolonged into a bony canal ex-
ternally, though often developing a partial bulla on their
inner side.

The mandible has a distinct angular process.

Order RODENTIA. — In the Rodentia the cerebral cavity is
generally elongated, depressed, somewhat broad behind and
narrow anteriorly. The occipital plane is more or less
vertical : the cerebellar fossa altogether behind the cerebral,
and the tentorial plane, or division between these fossae
approaching the vertical. The anterior part of the cerebral
fossa is contracted ; the olfactory fossa is of moderate size,
and situated directly in front of the cerebral.

The nasal cavities are very large, and both sets of
turbinals well developed, including an upper or nasoturbinal
lamella. The olfactory chambers attain their maximum of
development in some of the Porcupines (JfystrL-c], where
nearly all the bones of the upper part of the cranium are
expanded by great air sinuses formed within their walls. In
the Hare, and some others, the two optic foramina in the
orbitosphenoids are confluent ; and in consequence, in the
dried skull, there is a direct aperture of communication
between the orbits above the craniofacial axis.

The supraoccipital is more or less vertical, and does
not extend far on to the upper surface of the cranium.
There is often a distinct interparietal. There are generally

x.] RODENTIA. 179

moderately developed paroccipital processes, which in the
Capybara (Hydrocharus) are of great length, curving for-
wards and compressed laterally. They are also very large
in the Coypu (Myopotamus).

The parietals are moderate or small. The frontals, except
in the Squirrels, Marmots, and Hares, have little more than
a rudiment of a postorbital process, and there is never any
marked corresponding process arising from the zygoma, so
that the orbit is perfectly continuous with the temporal fossa.
The latter is always very small.

In a very remarkable East African genus, Lop/iiowys, a
broad bony lamella extends from the upper part of the
parietal outwards and downwards to join a similar ascending
plate from the malar, and thus forms an arched covering
to the temporal fossa, an arrangement unknown in any
other Mammal, but recalling that met with in the Tortoises.
The whole of the superior surface of the cranial bones of
this animal are covered with miliary granulations, disposed
with perfect regularity and symmetry.1

The nasals in Rodents are both long and wide, and
generally extend so far forwards as to make the anterior
nares quite terminal and vertical, or even with a downward
inclination. In Hystrix their development is enormous, but
this is chiefly owing to their breadth and backward extension
over the great nasal chambers and air sinuses. They are
narrowest in Jiathyergus and its allies.

The premaxillai are large, and lodge the great curved
incisor teeth,'- and always send a narrow prolongation back-
wards by the side of the rasals to join the frontals.

1 See A. Milne-Edwards, Xour. Archiv. du Museum, iii. 1867.

2 These teeth, though first developed in the gum covering the pre-
maxilla, have their roots, when fully developed, in the maxilla. This
does not invalidate their determination as incisors.

N 2

i8o

THE SKULL.

[CHAP.

In the larger number of Rodents there is a great vacuity
in the anterior or maxillary root of the zygoma of varying size
and form, apparently an enormous dilatation of the infra-
orbital foramen, and through which a portion of the masseter
muscle passes (see Fig. 59). It is sometimes as large as the
orbit itself, with which it communicates freely posteriorly
underneath a vertical bar, formed by the maxilla in front, and
by the lacrymal and malar behind. Its inferior boundary

.Va

\OSFrAS

Per

A a nasal; P\Ix premaxilla ; 3Ix maxilla ; Ma, malar; 7V tympanic ; ExO ex-
occipital ; Per points to the large supratympanic or mastoid bulla.

is a slender zygoma-like horizontal bar, formed by the maxilla
alone. In the Rats it is a vertical fissure dilated superiorly.
In the Viscacha (Lagostomus), the true infraorbital foramen
is separated from the large antorbital vacuity by a thin as-
cending bony lamella. In Castor, Leptis, Bathyergus, Sa'urus,
Arctomys and some others, the infraorbital foramen is of the
usual size.

In the Hares, the facial surface of the maxilla is curiously
reticulated.

x.] RODENTIA. 181

The zygoma is present in all, of various degrees of thick-
ness, but always either straight or more or less curved
downwards, and usually not much arched outwards. Its
anterior and posterior roots are formed by the maxilla and
squamosal respectively, the malar intervening. In many
cases the last-named bone extends backwards, applied to the
under surface of the zygomatic process of the squamosal to
form the outer side of the glenoid articular surface. In
the spotted Cavy (Caelogcnys), the zygoma has an enormous
vertical expansion, with a rugose or pitted outer surface,
and a large fossa in the inner side of the maxillary portion
with which the cavity of the mouth communicates in a
recent state.

The lacrymal bone usually presents both orbital and
facial surfaces, but the orifice of the canal (lacrymal foramen)
is always well within the margin of the orbit. In the Beaver,
and many others, the facial portion is reduced to a mere
tubercle, and in the Hare the lacrymal is entirely within
the orbit.

The j>alate of the Rodents is usually narrow. In the long
space intervening between the incisor and molar teeth, it
has no definite lateral margins, but rounds off insensibly on
to the sides of the face. In this region the anterior palatine
foramina form very conspicuous longitudinal slits, of specially
large size in the Hares. The portion of the palate situated
between the molar teeth is often very narrow anteriorly
and ends posteriorly in a thickened excavated border. In
the Hare it is reduced to a short transverse bridge, ex-
tending across the middle line between the premolar teeth.
In the Capybara and Guinea Pig the alveolar border of the
maxilla is very long, and presents the remarkable peculiarity
of extending backwards beneath the orbit to unite with the
squamosal at a level with the anterior border of the glenoid

1 82 THE SKULL. [CHAP.

fossa. It thus forms the outer border of a large conical
cavity, opening posteriorly, bounded on the inner side by
the pterygoids, above by the alisphenoids, and below by the
palatines.

The pterygoids are always simple subquadratc lamella;,
early ankyloscd with the basisphenoids, often sending a
well-marked hamular process backwards, which unites with
the auditory bulla in Hystrix, Lagostowtts, Bathycrgits, &c.
There are usually well-marked ptcrygoid fossas, and the sides
of the alisphenoids are often perforated by an alisphenoid
canal. In Hystrix the hamular process is slightly bullate.
The squamosal forms a considerable part of the outside wall
of the cranium, but in consequence of the large size of the
united tympano-periotic, the root of the zygomatic process is
thrown very forward on the side of the skull, and the pos-
terior part of the body of the squamosal which unites with
the occipital is reduced to a long, rather narrow strip,
interposed between the parietal and pcriotic. When the
mastoid bulla; are greatly developed, as in Pcdetcs (see Fig.
59), this does not reach as far backwards as the occipital,
and is a slender curved process, which clasps the outside of
the bulla, and appears to hold it in its place.

The glenoid fossa is situated on the under side of the
posterior root of the zygoma. In its most typical form (as
in the Capybara, Viscacha, Aguti, Paca, etc.) it is narrow and
concave transversely, with prominent inner and outer edges,
the latter being often formed, as before mentioned, partly by
the hinder end of the malar. In the Beaver the glenoid fossa
has considerable breadth. In the Porcupines, Marmots,
Squirrels, Rats, etc., no raised inner margin is developed,
and the fossa passes insensibly into the side of the skull wall.
In the Hare it is a transversely oval hollow, with a prominent
rounded anterior margin.

x.] RODENTIA. 183

The tympanic is ankylosed to the periotic, but not to the
squamosal ; it generally develops a tubular meatus, which in
the Hare is directed upwards and backwards, in the Beaver,
outwards and forwards. In the Porcupines, as well as in
most of the smaller Rodents, the meatus is short. In the
Capybara it is fissured below.

There is always a considerable tympanic bulla, which is
often supplemented by a bulla developed above the tympanic
cavity apparently in the periotic. In some genera (Pedetes,
Difus, Chinchilla'] this attains an enormous size (see Fig.
59, Per), and forms a rounded prominence on the posterior
external angle of the skull, interposed between the squamosal,
parietal, and occipital. Usually, the mastoid portion of the
periotic only appears on the surface for a small space in front
of the exoccipital. In the Beaver, it forms a conspicuous
angular process.

The periotic is never ankylosed with any of the bones of
the cranium, other than the tympanic. On its inner surface
the floccular fossa is nearly always wide and deep, but it is
absent, or nearly so, in the Capybara, Paca, and Porcupine.
The place of attachment of the hyoid arch is an inconspicuous
depression in the usual situation, and the tympanohyal is
never distinct. This is in relation with the rudimentary
condition of the anterior cornu of the hyoid.

In the mandible, the symphysial portion is narrow, curving
upwards, and rounded laterally, with a single large alveolus
on each side. The coronoid process is never large, and is
often rudimentary or absent, in relation to the small develop-
ment of the temporal fossa and muscle ; while the portion
adjacent to the angle is greatly developed, showing marked
masseteric and pterygoid fossae, and often with its lower
edge expanded laterally, or slightly incurved. The angle is
rounded in the Hares, but it is more often produced into a

1 84 THE SKULL. [CHAP. x.

long backward process, more or less pointed and upturned.
The condyle is considerably elevated, with a rounded
articular surface, usually longer from before backwards than
from side to side.

The hyoid has a transversely extended basihyal and a
straight compressed rod-like thyrohyal, often ankylosed with
the basihyal. The anterior arch is long, but mostly liga-
mentous, the ossification being usually confined to the lower
part (cerato- and epi-hyals). In the Hares, the basihyal is
deep from above downwards, and compressed, keeled, or
pointed in front.

CHAPTER XI.

THE SKULL IN THE UNGULATA, HYRACOIDEA, AND
PROBOSCIDEA.

Order UNGULATA ; Sub-order Perissodactyla. — In the
Horse the whole skull is greatly elongated, chiefly in con-
sequence of the immense size of the face as compared with
the hinder or true cranial portion. The basal line of the
skull from the lower border of the foramen magnum to the
incisor border of the palate is very nearly straight. The
occipital and ethmoid planes are nearly perpendicular to this
line, the latter inclining slightly forwards. The tentorial
plane, strongly marked by inward projecting ridges of bone,
slopes obliquely backwards at an angle of 45°. The cerebral
fossa is a smooth and regular oval, broad and rounded in
front, and with no distinct division into anterior and pos-
terior portions. The olfactory fossa is short, but deep from
above downwards. The pituitary fossa is very shallow, and
there are no distinct clinoid processes. The alisphenoid is
very obliquely perforated by the foramen rotundum, but the
foramen ovale is confluent with the large foramen lacerum
medium behind. There are considerable frontal and sphen-
oidal air sinuses, but the former do not extend any great
distance over the brain-cavity.

iS6 THE SKULL. [CHAP.

In front of the cerebral cavity, the great tubular nasal
cavities are provided with well-developed turbinal bones, and
are roofed over by very large nasals, broad behind, and ending
in front in a narrow decurved point. The opening of the
anterior nares is prolonged backwards on each side of the
face between the nasals and the elongated slender premaxillo3.
The latter expand in front, and are curved downwards to form
the semicircular alveolar border which supports the large
incisor teeth.

The orbit is rather small in proportion to the size of the
whole skull, but very distinctly marked, being completely
surrounded by a strong ring of bone with prominent edges.
The lacrymal occupies a considerable space on the flat
surface of the cheek in front of the orbit, and below it the
malar does the same. The latter sends a hori/ontal or
slightly ascending process backwards below the orbit, to
join the under surface of the /.ygomatic process of the
squamosal, which is remarkably large, and instead of ending
as usual, behind the orbit, runs forwards to join the greatly
developed postorbital process of the frontal, and even forms
part of the posterior and inferior boundary of the orbit — a
very exceptional arrangement (see Fig. 60).

The palate is very narrow in the interval between the
incisor and molar teeth, in which are situated the large
anterior palatine foramina. .Between the molar teeth it is
broader, but it does not extend further back than the pen-
ultimate molar and ends in a rounded excavated border. It
is mainly formed by the maxillai, as the palatines are very
narrow. The pterygoids are delicate slender slips of bone
attached to the hinder border of the palatines, and supported
externally by, and generally ankylosed to, the rough pterygoid
plates of the alisphenoid, with no pterygoid fossa between.
They slope very obliquely forwards, and end in curved,

XI.]

PERISSODA CTYLA.

187

compressed, hamular processes. There is a distinct alis-
phenoid canal for the passage of the internal maxillary artery.
The base of the cranium is long and narrow. The glenoid
surface for the articulation of the mandible is greatly extended
transversely, concave from side to side, convex from before
backwards in front and hollow behind, and is bounded

Fir,. 60. — Side view of the posterior part of the skull of a Horse, j. Fr frontal (the
line points to the jxisturbita! process); Sq squamosal ; 1'a parietal: SO supra-
occipital; ExO cxoccipital : oc occipital condyle : /»/ paroccipital process; /Vr
nia-.ti.iil portion of periotic ; // post-tympanic process of squamosal : th tympano-
hyal ; Ty tympanic : f>g postglenoid process of squamosal ; As alisphenoid (inc-
line points to the plate of the bone which bridges over the alisphenoid canal); Ma
malar.

posteriorly, at its inner part, by a prominent postglenoid
process (Fig. 60, j>g).

The squamosal (S</) enters considerably into the forma-
tion of the temporal fossa, and besides sending the zygo.
made process forwards, it sends down behind the meatus
auditorius a post-tympanic process (//), which aids to
hold in place the otherwise loose tympano-periotic bone.

1 88

THE SKULL.

[CHAP.

Behind this the exoccipital gives off a very long paroccipital
process (//).

The periotic and tympanic are ankylosed together, but not
with the squamosal. The former has a wide but shallow
floccular fossa on its inner side, and sends backwards a
considerable " pars mastoidea " which appears on the outer
surface of the skull (Per) between the
post-tympanic process of the squamosal
and the exoccipital. The tympanic (Ty}
forms a tubular meatus, directed out-
wards and slightly backwards. It is
not dilated into a distinct bulla, but
ends in front in a pointed styliform
process which forms part of the outer
wall of the Eustachian canal. It com-
pletely embraces the truncated cylin-
drical tympanohyal (///), which is of
great size, corresponding to the large
development of the whole anterior arch
of the hyoid.

The stylohyal (Fig. 61, s/i) is of great
size, compressed, and expanded at the
upper end, where it sends off a tri-
angular posterior process. Below the
FIG. 61.— Superior surface stylohyal, and usually becoming anky-

of hyoid bones of horse, , , . , . ,, , , ,

i. sA stylohyal ; ch cera- losed with it, is a small nodular bone

tohyal ; bh basihyal ; tk / ••> i\ 11 .1 ,

thyrohyal. (6PlnyaV> ar>d tnen t'16 ar°h IS COm-

pleted by a short cylindriform cera-
tohyal (c/i). The basihyal (M) is rather flattened from
above downwards, arched with the concavity behind, and
sends forwards a long, median, pointed, compressed
" glossohyal " process. The thyrohyals (///) are compressed
bars projecting backwards from, and in adult animals

XI.] PERISSODACTYLA. 189

completely ankylosed to, the lateral extremities of the
basihyal.

Each ramus of themandible has a long, straight, compressed
horizontal portion, gradually narrowing towards the symphysis,
where it expands laterally to form with the ankylosed opposite
ramus the wide semicircular, shallow, alveolar border for
the incisor teeth. The region of the angle is expanded and
compressed, with a thickened rounded border without any
process. The condyle is greatly elevated above the alveolar
border ; its articular surface is very wide transversely, and
narrow and convex from before backwards. The coronoid
process is slender, straight, and inclined backwards.

The skull of the Rhinoceros resembles that of the Horse
in many essential features, but the occipital region is of
much greater extent vertically, the form of the cranial cavity
being concealed externally by large occipito-parietal air-
cells. There is no postorbital process to the frontal, so
that the orbit is not divided from the temporal fossa.
There is a conspicuous, rough, antorbital projection on the
lacrymal bone just in front of the lacrymal foramen
The nasals are very large and strong, early ankylosed to
gether, arched from before backwards, and pointed anteriorly.
The most elevated part of their upper surface is roughened,
and supports the great median horn which characterises
the genus. In some species a posterior rough, "but less
elevated, surface indicates the attachment of a second
horn. In some of the extinct species the mesethmoid
cartilage was ossified nearly as far forwards as the extremity
of the nasals, which is not the case with any existing
species. The premaxilloe are very small, and do not extend
anteriorly beyond the level of the front end of the nasals.
The hinder border of the palate is deeply excavated, the

igo THE SKULL. [CHAP.

horizontal plates of the palatines being very narrow. The
pterygoids are very slender, as in the Horse, but placed more
vertically. There is a distinct alisphenoid canal. The
squamosal sends down a very long, conical, postglenoid
process parallel with, and equalling, or sometimes exceeding,
in length, the paroccipital process. In all existing two-
horned species (7?. sumatrensis, bicornis and simus) the
meatus auditorius lies in a deep groove between the post-
glenoid and the post-tympanic processes of the squamosal.
In the one-horned species (R. unicornis and sondaicus) these
processes unite below so as to completely surround the
meatus. The post-tympanic process articulates with the
exoccipital, completely excluding the mastoid from the
external surface of the skull.1

The tympanic and periotic are ankylosed together, but
not with the squamosal. They are both very small. The
under surface of the tympanic is rough, forms no distinct
bulla, and is much encroached upon posteriorly by the very
large tympanohyal, which presents a circular, slightly concave,
rough, inferior surface, half an inch in diameter (in an adult
Sumatran Rhinoceros). Externally, the tympanic is pro-
duced into a rough, irregular, inferior wall to the auditory
meatus. The periotic internally shows the internal auditory
meatus near its lower part, but no distinct depression for
the flocculus ; it is prolonged upwards and outwards into
a small mastoid portion, which, as before said, does not
appear on the outer surface of the skull.

The mandible has a very wide condylar articular surface,
and slender recurved coronoid process, a rounded, somewhat
incurved angle, a compressed, rather narrow, horizontal por-
tion, and a shallow depressed symphysis.

1 See W. PI. Flower, " On seme Cranial and Dental characters of the
existing species of Rhinoceros." (Proc. Zool. Soc. 1876.)

XI.] PERISSODACTYLA. 191

The hyoid is much like that of the Horse, and has a
glossohyal process from the middle of the basihyal.

The Tapirs present some singular modifications of the
same type of skull.

As in the Rhinoceros, there is no separation between the
orbit and temporal fossa, but the anterior nares are of
immense size, and extend backward above the orbits, being
separated from them only by a thin plate of bone instead
of a broad flat surface, as in the Horse and Rhinoceros.
The nasal bones are short, broad behind, pointed in front,
much elevated, and supported by a tolerably well ossified
mesethmoid, which spreads out laterally at its upper end.1
The inferior and lateral margins of the great narial apertures
are entirely formed by the maxillae, which extend up to meet
the nasals, the premaxillx not taking any share in them. The
ethmo-turbinals are small, while the maxillo-turbinals, on the
other hand, are very extensive, though their plications are
comparatively simple. A conspicuous feature in the upper
part of the face is a groove, which extends backwards on
the side of the dilated hinder end of the nasal bone, and
curves inwards to form a rounded depression over the naso-
frontal suture. The form and size of this depression vary
in different species. It lodges an air sinus, with cartilaginous
walls extending upwards from the nasal chamber. In front
of the nares the rostrum formed by the maxillsi with the
premaxillna in front is produced, compressed anteriorly, and
curved downwards.

The base of the cranium resembles generally that of
the other Perissodactyla. There is an alisphenoid canal, and

1 In one species ( T. Dairdii) the ossification of the mesethmoid extends
far in advance of the nasal bones, and is clasped and suppDrted below
by ascending plates from the maxillae.

192 THE SKULL [CHAP.

large post-glenoid and post-tympanic processes ; the latter
joins the paroccipital process of the exoccipital, but above
their point of union a narrow slip of the mastoid appears
on the surface of the skull. The periotic is not ankylosed
to the squamosal or to the tympanic, which is exceedingly
rudimentary, forming a small irregular floor to the tympanic
cavity, with an oval lip for the attachment of the membrana
tympani, and always becomes detached in macerated skulls.

The mandible is chiefly noticeable for the great rounded
incurved posterior projection of the angle.

The hyoid has a simple, elongated stylohyal without pos-
terior process at the upper end, but one other ossification in
the anterior cornu, and no glossal process to the basihyal.

Sub-Order Artiodadyla. — The skull of the Sheep, as one
of the best known and easily procurable examples of this
group, may be first described, though in some respects it
is rather peculiarly modified.

On comparing the section of the cranium (Fig. 62) with
that of the Dog, it will be seen that there is a great difference
in the relation of the principal elements to each other, inas-
much as the face is bent downwards on the basicranial axis,
so that when the latter is horizontal, the upper surface of
the face looks forwards and the palate backwards. The
occipital foramen is terminal posteriorly, the tentorial plane
nearly vertical, so that the cerebellar fossa is altogether
behind the cerebral, but the plane of the cribriform plate
is horizontal, and the olfactory fossa altogether beneath the
anterior portion of the cerebral fossa.

The occipital region is small and sloping forwards.
There are long paroccipital processes (//). In very young
skulls a distinct interparietal bone is present, but in the
specimen figured this has coalesced with the supraocci-
pital (SO). The two parietals (Pa) unite very early at the

XI.]

AKTIODACTYI.A.

193

sagittal suture. The frontals (Fr) are large, and usually
(except in some domestic races) develop from their outer
surface conical, curved, bony processes, cancellous within,

*

FIG. 62 — Longitudinal and vertical section of skull of a Sheep (Otn's artts), i.
I'Mt premaxilla ; MT roaxillo-turbinal ; Na nasal; E'J' ethmolurbinal ; ME
mcsethinoid ; hr frontal ; OS orbitosphenoid : AS alisphenoid ; t'a parietal :
SO supraoccipital ; Per periotic ; ExO exoccipital ; BO basioccipital ; fp par-
occipital process ; Ty styhform process of tympanic; US basisphenoid ; PS pre-
sphenoid ; Pt pter>'goid ; /'/ palatine ; Vo vomer ; MX maxilla ; cp coronoid
process ; rd condyle ; s symphysis of mandible ; sA stylohyal ; eh epihyal ck
ccratohyal ; M basihyal; th thyrohyal.

which are called the " horn cores," as they form the internal
support of the true horns. The nasals (Na) are long and
pointed in front. The premaxillse (PMx) are slender, with

194 THE SKULL. [CHAP.

a shallow alveolar border, bearing no teeth and forming the
anterior and lateral boundaries of large anterior palatine
foramina. The lacrymals are large, and form a considerable
portion of the side of the face in front of the orbit, but the
foramen is entirely within the margin.

The olfactory chamber is larg *. The turbinals are greatly
developed ; the upper lamina of the ethmoturbinal or " naso-
turbinal " is distinct, and extends over the scroll-like maxillo-
turbinal (MT\ but does not ankylose with the nasal.

The orbit is large, nearly circular, with a complete,
prominent margin, formed below by the large malar, which
extends considerably on the side of the face, and posteriorly
sends a process upwards to meet the postorbital process of
the frontal, and is continued backwards to join the zygomatic
process of the squamosal.

The palate bones (PI) are of moderate, extent ; their
horizontal plate is deeply notched posteriorly. The pterygoids
(Pt) are broad above, but end below in a narrow lamella,
with a hamular process projecting backwards. The basi-
occipital (13O), seen from below, is square, with eminences
for muscular attachments at each of its four angles. The
basisphenoid (£S) is much contracted laterally. The pos-
terior clinoid processes are large, and the pituitary fossa
deep.

The squamosal is small, and scarcely appears in the interior
of the skull. The glenoid facet is rather extensive, and
slightly convex, and there is a postglenoid process and
foramen. The tympanic is not ankylosed to the periotic ; it
forms a complete tubular external auditory meatus, and a
considerable, but simple, bulla, narrowing to a sharp-pointed
process anteriorly (Ty). The periotic (Per) is rather small,
without any fossa for the flocculus ; its mastoid portion
forms a distinct, narrow, rough surface on the outer side of

xi.] ARTIODACTYLA. 195

the skull, between the hinder border of the squamosal and
the exoccipitaL The tympanohyal is very large, cylindrical,
curved, and almost completely embedded in the tympanic,
between the inferior wall of the meatus and the outer wall
of the bulla.

The extracranial portion of the hyoid consists of large
compressed stylohyals (sh), with a prominent posterior
process near the upper end, short but well-ossified epi-
hyals (eh] and ceratohyals (ch), and a basihyal represented
by a small rounded nodule of bone, to which the straight
thyrohyals (//*) are not ankylosed.

The mandible has a broad flat condyle (cd], a long slender
coronoid process (r/), a rounded angle, a rather slender
horizontal portion, contracted and with a sharp upper edge
in front of the molar teeth, and expanded anteriorly for the
lodgment of the incisors.

The Ox agrees generally with the Sheep in its cranial
characters. The face is bent down on the basicranial axis
almost in the same manner. The occipital surface is flat,
and terminates above in a broad transverse ridge, which
extends between the horn cores. The parietals are ex-
tremely narrow above, and placed almost entirely behind
this ridge. They unite very early with the interparietal and
supraoccipital. The intercornual ridge of the frontals is
excavated by large air-cells, communicating with those of
the horn cores, and is especially developed when the horns
are large. Unlike the parietals, the frontals are of very
great extent, and have a broad and flattened upper surface.

The tympanics are compressed and scarcely at all bullate.
They end anteriorly in long compressed styliform processes,
and become firmly ankylosed with the periotic and squa-
mosal. The under surface of the meatus auditorius has a

o 2

i96 THE SKULL. [CHAP.

compressed ridge. The large tympanohyals are entirely em-
bedded in the tympanic, only the rough lower surface for
articulation with the stylohyal being exposed.

The mandible and hyoid are like those of the Sheep, but
the basihyal is rather more developed, and has a rounded,
anterior, median projection.

Many Ruminants (especially among the Cervidcc} have a
vacuity of varying extent on the side wall of the face,
between the frontal, lacrymal, maxillary and nasal bones,
leading in the macerated skull into the nasal chamber, but
closed in the living animal by membrane. Most of the
Deer and Antelopes have also a large depression on the
facial surface of the lacrymal bone, called the suborbital or
lacrymal fossa, though it has nothing to do with the tears,
but lodges a glandular fold of the integument, which secretes
a peculiar unctuous and odorous substance. In most Deer
the orifice of the lacrymal canal is double, and situated on
the margin of the orbit, whereas in most of the hollow-
horned ruminants it is single and placed well within the
margin. There are however exceptions in both cases.

In the Deer the axis of the face is nearly in the same
line with that of the cranium, so that when the basicranial
axis is horizontal the nose is directed forwards instead of
downwards, as in the Sheep and Ox. The animals of this
family have no permanent horn cores continuous with the
cranium and ensheathed by true horns, but have short pro-
cesses on the frontal bones (pedicles], from which branching
antlers of true osseous structure are annually developed and
shed. These, as a rule, are only present in the males,
while the horns of the Bovida and Antilopida are usually
common to both sexes.
_. Among the Antelopes, the Saiga (Saiga tartaricd) is very

xi.] AKTIODACTYLA. 197

remarkable for the conformation of the upper part of the
face. The anterior nares extend backwards almost to a
level with the front edge of the orbits, and have an unusual
vertical expansion. The nasal bones are aborted or coa-
lesced with the frontals. The turbinals are very short.
The lacrymals enter largely into the side walls of the
anterior nares. The ascending processes of the premaxillse
are small, and very widely separated from the nasals. In
the living animal the edges of these greatly expanded narial
apertures are continued forwards into a truncated, almost
proboscidifonn muzzle without any bony support, giving the
contour of the face a totally different appearance from that
presented by the skull.

In the Elk (Alces), and a small Abyssinian Antelope
(Neotragus saltiand), the nasal bones are very much shorter
than they are in ordinary ruminants.

The Tylopoda (Camels and Llamas) and the Tragulina
differ from most of the Pecora^ and resemble the non-rumi-
nating Artiodactyles in having the tympanic bulla filled with
cancellated bony tissue.

The skull of the Pig shows in section that the axis of the
face is bent down upon the basicranial axis almost as much
as in the Sheep, a disposition which increases with age.
Though the form of the cranial cavity is not very different
from that of the Sheep, the external appearance of the
hinder-part of the skull is greatly changed by the elevated
and backward sloping occipital crest, formed by the union
of the supraoccipital (concave from side to side posteriorly)
and the parietals. The latter have their outer and inner
surfaces widely separated in the adult Pig by large air-cells.

The frontal is broad and flat between the orbits, and
sends out a small postorbital process, which does not join the

ig8 THE SKULL. [CHAP.

zygoma. The face is greatly elongated, tapering forwards,
and compressed laterally. The nasals are long and narro\v,
and the apertures of the nares small and nearly terminal.
The premaxillae send up long processes on each side of
the nasals, which, however, do not meet the frontals. The
lacrymal has a considerable facial portion ; and, as in
other Ungulata, the malar encroaches considerably on the
face, uniting with the lacrymal.

At the anterior extremity of the mesethmoid a peculiar
ossicle (prenasat) is developed, which strengthens the cartil-
aginous snout.

The palate is long and narrow, and extends posteriorly
beyond the last molar tooth. The pterygoid fossae are well
marked, being chiefly formed by the well-developed ptery-
goid plates of the alisphenoid ; the true pterygoids are very
slender. There are very long, slender, compressed par-
occipital processes, curved forwards.

The squamosal and tympanic are ankylosed together ; the
floor of the long, narrow, upward-directed auditory meatus
is formed by the tympanic, wedged in a cleft of the squa-
mosal, between the hinder edge of the glenoid fossa (there
being no postglenoid process) and a long descending post'
tympanic process which articulates with the exoccipital.

Inferiorly the tympanic is dilated into a very prominent
bulla, peculiarly elongated vertically, and rather compressed
from side to side. The interior of this bulla is filled with
cancellous bony tissue.

The periotic is small and not ankylosed to the tympanic
or squamosal. The mastoid portion is quite rudimentary,
being merely a short scale-like prolongation upwards and
backwards, lying on the inner surface of the squamosal, and
making no appearance on the external surface of the skull.
The tympanohyals are very inconspicuous, being small, and

xi.] ART10DACTYLA. 199

situated at the bottom of a deep fossa on the outer and
posterior side of the tympanic bulla.

The mandible has a high ascending portion behind, a
transverse condyle, a very small coronoid process, and a flat
expanded angle, rounded posteriorly.

The hyoid of the Pig is very different from that of most
other Ungulata. The basihyal is very small. The thyrohyals
are large, broad and flat, and ankylosed to the basihyal, but
with their extremities cartilaginous even in old animals.
There is a well-ossified ceratohyal, not ankylosed with the
basihyal, but the greater part of the anterior arch is a long
cartilaginous band, with one, or sometimes two, slender
ossifications near the middle part, representing the stylohyal.

The skull of the Hippopotamus resembles that of the
Pig in many essential features, although its external form is
greatly modified. The brain cavity is very small, and the
face immensely developed. The orbits project outwards in
an almost tubular manner, and their margins are nearly, and
in some cases quite, complete posteriorly. The face is con-
tracted laterally in front of the orbits, and then expands
widely into a massive truncated muzzle, which supports the
great canine and upper incisor teeth.

The anterior narial orifice is nearly circular ; it is bounded
by the extremities of the narrow but greatly elongated
nasals above, and laterally by the prominent, rounded,
rugged and massive premaxillae. At the anterior and lower
part of the orbit, the lacrymal is dilated into a great thin-
walled bony capsule, of such delicacy that it is nearly always
destroyed in the skeletons preserved in museums. This
opens into the nasal air-passages and has no connection
with the lacrymal apparatus. A similar but smaller dilatation
exists in many of the Pecora.

200 THE SKULL. [CHAP.

The palate is long and narrow, and extends posteriorly a
short distance behind the last molar teeth. The internal
pterygoids end in well-marked stout hamular processes. The
glenoid surface of the squamosal is very much extended,
but not bounded externally by a projection from the malar
as in the Pig, and the inner half of its posterior margin is
produced into a tolerably well marked postglenoid process.
The paroccipital process is long and conical, but far less
conspicuous than in the Pig. The tympanic bulla is pro-
portionately smaller, and of a trihedral form, ending in an
antero-inferior pointed process. Its interior is filled with
cancelli, as in the Pig. As in that animal, there is a long
narrow meatus auditorius, directed upwards and backwards
in a fissure between the postglenoid and post-tympanic
processes of the squamosal, the floor being formed by
a compressed, ridged prolongation of the tympanic,
which is at a very early age completely fused with the
squamosal. The periotic is very small, remains longer
distinct, though ultimately ankylosing with the conjoined
squamoso-tympanic, and has only a rudiment of a mas-,
toid portion, which is quite confined to the interior of the
cranium.

The tympanohyal is slender, ankylosed to the back of the
tympanic, and in the adult skull sunk in a deep fossa,
between that bone and the exoccipital, which also gives exit
to the facial nerve.

The mandible is of immense size and weight. The
condyles rise very little above the level of the molar teeth.
The coronoid process is small and much recurved. The
angle is greatly expanded and everted, rounded behind, and
terminating below in a distinct process, projecting down-
wards and forwards. The horizontal rami are compressed
in their middle portion, but widen anteriorly into a very

xi.] HYRAC01DEA. 201

broad and massive truncated symphysial portion, which
supports the huge incisor and canine teeth.

In the hyoid apparatus, the basi- and thyro-hyals anky-
lose, and are something like those of the Pig. The an-
terior arch consists of three well-ossified pieces of subequal
length.

HYRACOIDEA. — The skull of the Hyrax presents many
affinities with that of the Perissodactyla, others with the
Rodentia, and some characters peculiar to itself.

The cranium is high and truncated behind, the occiput
nearly vertical, the tentorial and olfactory planes oblique,
the olfactory fossa rather small.

There is a small distinct interparietal. The frontal region is
broad and flat. The zygoma is tolerably strong, and consti-
tuted mainly by the malar, which extends so far backwards as
to form the outer wall of the glenoid fossa, but it is supported
anteriorly by a strong process from the maxilla. The orbit
is bounded posteriorly by well-marked postorbital processes
which sometimes meet, the lower one from the malar, and
the upper one from the parietal (a very unusual condition).
The lacrymal is small, and scarcely extends at all on to
the face, but sends outwards a strong antorbital process (as
in the Rhinoceros and Elephant). The face is short, and
compressed laterally. The nasal bones are wide posteriorly,
and anteriorly are either truncated, or more produced at
their outer than their inner margins. The premaxillae do
not send up processes to meet the frontals, as in all
Rodents.

The palate is not produced posteriorly beyond the middle
of the last molar tooth. The palate bones are large. The
ptervgoids very slender. There are well-marked pterygoid
fossse, and alisphenoid canals. The paroccipital processes

202 THE SKULL. [CHAP.

are long and slender. The glen old fossa is wide transversely,
and with a considerable postglenoid process. The periotic
and tympanic are ankylosed together, but usually remain
distinct from the squamosal. The tympanic forms a
moderate-sized bulla, and a spout-like floor to the external
auditory meatus, between the glenoid and post-tympanic
processes of the squamosal. The periotic has a very slight
floccular depression, and sends backwards no distinct mas-
toid process. The pituitary fossa is very shallow, without
clinoid processes. The foramen rotundum and foramen
ovale are distinct perforations through the alisphenoid. The
optic foramen pierces the large orbitosphenoid near its
hinder margin.

The mandible has a high and exceedingly broad ascending
portion, its hinder margin being produced far behind the
condyle, but the angle is rounded, and without any distinct
process. The condyle is much extended transversely, and
narrow from before backwards, especially in its inner half,
for externally it is somewhat rounded. The coronoid pro-
cess is small and recurved.

The hyoid apparatus of the Hyrax s unlike that of any
other known Mammal. The basihyal is oval, transversely
extended and flat, with a small median eminence on its
anterior border, and an emarginate posterior border, only
ossified in the centre, and prolonged laterally, without any
definite segmentation, into broad, flattened, slightly curved
cartilaginous thyrohyals. Articulated to the anterior and
external angles of the basihyal are two large, triangular,
flattened bones (ceratohyals), each with a long process
projecting forwards and meeting in the middle line, so
as to enclose (with the anterior margin of the basihyal) a
triangular space. There is no other cartilage or bone in the
anterior arch, unless a very minute pyramidal bone, described

XI.] PROBOSCIDEA. 203

by Brandt as articulating with the mastoid process of the
skull, represents the stylohyal.1

PROBOSCIDEA. — The skull of the only existing animals of
this group, the Elephants, presents many very remarkable
features. As the brain-case increases but little in size
during growth, and as the exterior wall of the skull is required
to be of great superficial extent to support the trunk and the
huge and ponderous incisor teeth or rusks, and to afford
space for the attachment of muscles of sufficient size and
strength to wield the skull thus heavily weighted, an extra-
ordinary development of air-cells takes place in the can-
cellous tissue between the outer and inner surface walls or
" tables " of nearly all the bones of the cranium, separating
them in some cases as much as twelve inches apart (see
Fig. 64). These cells are not only formed in the walls of the
cranium proper, but are also largely developed in the nasal
bone and upper part of the premaxilla and maxilla, the bones
forming the palate and the basicranial axis, and even
extend into the interior of the ossified mesethmoid and
the vomer. Where two originally distinct bones come in
contact the cells pass freely from one to the other, and
almost all the sutures become completely obliterated in old
animals.

The intercellular lamellae in the great mass which sur-
rounds the brain-cavity superiorly and laterally mostly
radiate from the inner to the outer table, but in the other
bones their direction is more irregular. Like the similar but
less developed air-cells in the skulls of many other Mammals,
they are entirely secondary to the original growth of the
bones. In the young African Elephant's skull figured (from

1 "Mem. de 1'Acad. Imp. de St.-Petersbourg," Vile Serie, tomexiv.
No. 2, p. 68 (1869).

204 THE SKULL. [CHAP.

an animal about six months old, see Fig. 63), their formation
has scarcely commenced, and as the sutures are still quite
distinct, and the bones not distorted by these cellular
dilatations, they are in a much better state for studying
their connections and characteristics.

When the basicranial axis is placed in a horizontal position,
it will be seen that the foramen magnum is quite posterior,
and its plane nearly vertical. The cranial cavity is elongated
and depressed (more so in the African than the Indian
Elephant), the tentorial plane nearly vertical, so that the
cerebellar fossa is altogether behind the cerebral fossa. The
latter is broad behind and contracted laterally in front. The
olfactory fossa is large, and placed altogether below the
anterior part of the cerebral fossa, the cribriform plate being
nearly horizontal. The ridge which separates the anterior
from the posterior division of the cerebral fossa is very well
marked. The pituitary fossa is very shallow, and there are
no distinct clinoid processes. The supraoccipital (SO) is
high, and inclines greatly forwards ; so that the occipital sur-
face looks upwards as much as backwards. In the adult skull
(Fig. 64) the lateral parts of the occipital region (rounded
smoothly off in the young state) are vastly expanded and
leave between them a deep median depression, with a rugged
floor, and a partial bony septum at the bottom, into which
the ligamentum nuchae is inserted. The median portion of
the supraoccipital never becomes expanded by air-cells.
The parietals (Pa) are very large, and form the greater part
of the lateral walls of the cranium. The frontals (Fr) are
narrow from before backwards, and produced laterally into
elongate supraorbital processes, which send out small post-
orbital processes, not, however, completely separating the
small orbit from the large and high temporal fossa.

PROBOSC1DEA.
Jb Sir

205

SO

JVn

PMr

FIG. 63. — A section of the cranium of a very yvung African Elephant (ElrfJuu
a/rjfanns). taken s .rnpwh.it tj the right of the middle line, so that the (me^cih-
inoid and vomcr are removed, 4- The letters as in the other figures.

FIG. 64.— A section of the cranium of a fiill-gr^wn African Elephant, taken to the left
of the middle line, and including the vomer (Yo), and the mesethmoid (ME),
an anterior, and tit posterior narial aperture. i'j.

206 THE SKULL, [CHAP.

The most remarkable feature in the face is the form and
position of the anterior narial orifice (an). It is wide trans-
versely, very short from above downwards, placed very high,
and is directed upwards and forwards, almost as much as in
the Whalebone Whales. The nasal bones (No) which bound
it above are very thick, short, broad behind, and conical
in front, and contain large air-cavities. The inferior and
lateral margins of the orifice are formed entirely by the pre-
maxillas (PMx), which send processes up to join the nasals
and frontals. In front of the nares the face is prolonged
into a somewhat quadrate, depressed, alveolar process, trun-
cated in front, concave above, rounded laterally, formed by
the premaxillse above and at the sides, and by the maxilla;
below. This contains the roots of the great incisor teeth
or tusks.

The iacrymal is small, placed almost entirely within
the margin of the orbit, and ends anteriorly in a projecting
antorbital process. The zygomatic arch is slender and
straight, the malar being small, and forming only the middle
part of the arch, the anterior portion of which is (unlike
that of all Ungulates) formed by the maxilla.

The elongated, tubular nasal cavity forms a sigmoid
curve, being directed (from below) at first forwards, then
upwards, then forwards. The olfactory chamber is a
comparatively small fossa in the middle third of its posterior
wall, filled by the complex ethmoturbinals. The maxillo-
turbinals are but rudimentary, the narial passage being quite
free.1 The floor of the palate is completed posteriorly by
well-developed palatines (PI). The pterygoid (Pt) is slender
and very early ankylosed with the pterygoid process of the

1 The elongated proboscis probably supplies their place functionally
in warming and cleaning the inspired air.

XL] PROBOSCIDEA. 207

alisphenoid, which is greatly expanded, and hollowed in
front, being spread round the dilated posterior margin of
the alveolar portion of the maxilla, and aiding to close the
great alveolar cavity of the hindermost molar tooth.

The squamosal (Sy) forms a considerable part of the
cranial wall, extending outside the small alisphenoid to meet
the frontal, and externally sends off a broad post-tympanic
process, which meeting (though not uniting with) the hinder
border of the glenoid fossa in front, bounds the bony ex-
ternal auditory meatus, to which the tympanic contributes
very little. The latter bone is, in the young specimen, com-
pletely united with the periotic, but not with the squamosal.
Inferiorly it forms a large, rounded, but not very prominent
auditory bulla, deeply notched on its inner side by the
canal for the internal carotid artery (a). The periotic
(/Vr) presents a large surface within the cranium without
any floccular fossa. The mastoid portion is very small, and
does not appear on the surface of the cranium. There are
no paroccipital or postglenoid processes. At the bottom
of a deep fossa between the squamosal, exoccipital, and
tympanic, the tympanohyal is distinctly seen, with the
stylomastoid foramen to its outer side. The exoccipi-
tals are not perforated by a condylar foramen, neither
is the alisphenoid perforated, but it is grooved in front
for the foramen rotundum, and behind for the foramen
ovale.

The mandible is of a very peculiar shape. The ascending
portion of the ramus is high, and terminates in a rather
small rounded condyle, wider from side to side than from
before backwards. The posterior border is thick, but
rounded off gradually into the inferior edge, without any
projection at the angle. The coronoid process is compressed,

208 THE SKULL. [CHAP. xi.

and but very little elevated. The horizontal portion is very
massive and rounded to support the great molar teeth ; it
unites with its fellow in front in a narrow, prolonged, spout-
like symphysis.

The stylohyals are forked at their upper extremity, the
posterior process being greatly developed. They taper
below to a point which is connected by a long ligament with
the basihyal. The thyrohyals are long, compressed, and
ankylosed to the basihyal.1

3 See A. H. Garrod, Proc. Zool. Soc. 1875, P- 3^5-

CHAPTER XII.

THE SKULL IN THE CETACEA AND THE SIRENIA.

Order CETACEA. — The animals of this order exhibit some
remarkable modifications in the characters of the skull.

I will first select for description that of a young example
of one of the Odontoceti or Toothed Whales, the common
round-headed Dolphin or Globictphalus of our coasts. Fig.
65 represents a vertical median section of this skull. It
will be seen that the cerebral cavity is of a very unusual
shape, being short and broad, but extremely high and con-
tracted above — in fact, somewhat in the form of a truncated
cone, with rounded edges. The bones of the basicranial
axis are curved upwards at each extremity. They consist
of the ankylosed basioccipital (BO) and basisphenoid (BS)
separated by a vertical fissure from the presphenoid (PS)
and mesethmoid (M£), which are also ankylosed, though
their original line of separation can still be traced. The
pituitary fossa scarcely forms a distinct concavity, and the
clinoid processes are almost obsolete. The mesethmoid is
very large, and consists of (i) a high and broad vertical
plate, which closes in the vacuity between the frontals in
the anterior part of the cerebral cavity, and corresponds to

210 THE SKULL. [CHAP.

the cribriform plate of the ordinary Mammal, though with
but few and small perforations ; (2) an anterior rod-like,
somewhat compressed, pointed prolongation from the lower
part of this plate, which extends forwards in the groove of
the vomer ( Vo) almost to the extremity of the rostrum, and
which in great part remains permanently cartilaginous.
This corresponds with the septal cartilage of the nose of
other Mammals, although owing to the altered position of
the nares it has here little relation with these passages.

The cranial cavity is formed chiefly of the cerebral fossa,
the cerebellar fossa being relatively small, and the olfactory
fossa entirely wanting.

The optic nerve passes out through a deep notch, some-
times a foramen, in the hinder border of the orbitosphenoid.
The alisphenoid is not perforated, the foramen rotundum
being confluent with the large sphenoidal fissure, and the
foramen ovale with a large infundibuliform opening between
the alisphenoid, parietal, exoccipital, basioccipital, and basi-
sphenoid, in the bottom of which is seen the inner surface
of the periotic (Per), which in the Cetacea makes no projec-
tion into the cerebral cavity. The anterior part of this
opening corresponds to the foramen lacerum medium with
the foramen ovale, the hinder part to the foramen lacerum
posterius.1 The squamosal (,5V;) appears in the outer
boundary for a very small space, between the parietal and
the exoccipital. The condylar foramen pierces the ex-
occipital, near its anterior edge. The large or nearly
circular carotid canal has a peculiar position, passing
through the basisphenoid, near its middle, in a direction
from below upwards, forwards, and inwards.

1 In the adult of the same species, the foramen ovale is separated
from the large opening common to the seventh and eighth pair of nerves
by a strong bony partition formed by the ossified tentorium cerebelli.

XII.]

CETACEA.

211

The bones forming the walls of the cranial cavity are dis-
posed in a very remarkable manner. The occipital surface
is of great size, and slopes upwards and forwards. The
foramen magnum is large, and looks directly backwards ; its

Pa
SO

ExO

II

r<f

FIG. 65. — A section of the skull of a young Dolphin (Globictfikalui nielas), |. PMx
premaxilla ; MX m.ixill.i ; ME ossified portion of the mesethmoid ; an anterior
nares ; t<ln nasal ; //' interparietal ; /•> frontal ; Pa parietal ; SO supraoccipital ;
EjcO exoccipital ; KO basioccipital : Sq squamosal ; Per periotic ; AS alisphenoid;
PS presphenoid ; Pt pterygoid ; />n posterior nares ; PI palatine ; Vo vomer :
* symphysis of mandible ; id inferior dental canal ; ef cjronjid process ; erf con -
dyle ; a angle ; sh stylohyal ; bk basihyal ; th thyrohyaL

lower lateral margins are bounded by large oval condyles,
which meet in the middle line below, and are formed by
the exoccipitals, with a small portion of the basioccipital.
Above the foramen, the immense supraoccipital (SO), with
which an interparietal (IP) is ankylosed, extends forwards

212 THE SKULL. [CHAP.

beyond the vertex, to be wedged in between the frontals,
completely excluding the parietals from the upper region of
the cranium. These latter (Pa) form the greater part of the
sides of the narrow high temporal fossae, and are ankylosed
with the supraoccipital above, although the different elements
of the occipital are still distinct. The frontals (Fr) are broad
from side to side, being prolonged outwards into the arched
supraorbital plates, but are almost entirely covered by lamel-
liform extensions of the maxillae, which leave but a thin
strip of the frontals visible on the external surface of the
cranium. The temporal fossa is bounded below and in
front by a stout postorbital process of the frontal, very nearly
meeting the broad zygomatic process of the squamosal. The
orbit is elongated from before backwards ; at its anterior
extremity is a rounded antorbital prominence, formed by
the junction of the maxillae, frontal and malar ; below, it is
bounded by a long and very slender styliform zygomatic
process of the malar, which arises from near the anterior and
inner angle of the body of the bone, and passes backwards,
slightly curved downwards, to articulate with the extremity
of the zygomatic process of the squamosal. There is no
distinct lacrymal bone, or canal.

The special modification of the bones of the face has
relation chiefly to the peculiar position of the nasal passages,
which instead of passing forwards above the roof of the
mouth to the anterior extremity of the face, are directed
upwards and somewhat backwards towards the vertex of the
cranium ; the external narial orifices being situated quite on
the top of the head, the part which first appears above the
surface of the water when the animal rises for the purpose of
respiration. The whole nasal cavities are small, and they are
(as far as concerns their bony walls) simple canals, entirely
destitute of turbinals. Though their direction is in the main

xii.] CETACEA. 213

vertical, they are not straight, but curve round the anterior
end of the brain cavity, both upper and lower orifices (an and
/«) being directed somewhat backwards. They are com-
pressed from before backwards above, but wider and more
round below. The nasal bones (No), instead of being
lamelliform and roofing over the nasal passages, are reduced
to nodular masses, lying in depressions in the frontals, but
forming as usual the hinder boundary of the anterior narial
openings.

In front of these openings, the face stretches out into
an elongated, depressed, pointed beak, or rostrum, formed
by the premaxillae and maxillae surrounding the vomer and
mesethmoid cartilage. The premaxillae send prolongations
upwards to form the lateral boundaries of the narial orifice,
and it is remarkable that these are not quite symmetrical,
that of the left side being the shortest. The orifice itself,
moreover, is rather inclined towards the left. Between the
antorbital process of the maxilla and its rostral prolongation
is a deep notch, the "antorbital notch." The upper surface
of the face, near this notch, has several very large foramina
for the transmission of branches of the fifth nerve.

The elongated, pointed, and convex palate is formed
chiefly by the maxillae (Mx), the premaxillae (PMx) only
appearing for a short space near the apex. Behind the
maxillae, the palatines (PI) are somewhat wide laterally,
but towards the middle line form an exceedingly narrow
strip, inserted between the maxillae and the pterygoids (Pt) ;
the latter are greatly developed ; besides forming the outer
wall of the posterior nares, each sends a lamella inwards,
which nearly (in most Dolphins, completely) meets its fellow
in the middle line, and so prolongs the bony palate back-
wards. This process, moreover, is reflected outwards again
from its inner or lower edge, and, joining with a projecting

214

THE SKULL.

[CHAP.

plate from the palatine, incloses a large cavity, open only
behind, which contains the post-palatine air sinus. The

FIG. 66. — Under surface of the cranium of a young Dolphin (Globicepkalus welas). \.
BO basioccipital ; ExO exoccipital ; Per posterior (mastoid) process of periotic ;
Ty tympanic ; Sq squamosal ; AS alisphenoid ; OS orbitosphenoid ; ZM zygo-
matic process of malar ; Fr supraorbital process of frontal ; Ma body of malar ;
Pt pterygoid ; PI palatine ; MX maxilla ; PMx premaxilla ; Vo vomer ; gf
glenoid fossa of squamosal ; tg deep groove on squamosal for meatus auditonus
externus, leading to tympanic cavity ; cf condylar foramen.

vomer ( Vo) is of great si?e, extends forwards nearly to the
apex of the rostrum, embracing the mesethmoid cartilage,

xii.] CETACEA. 215

and posteriorly reaches for a considerable distance beneath
the basisphenoid. It forms as usual the inner wall of the
posterior narial apertures. Behind these apertures the base
of the skull is flat in the middle line, but with prominent
lateral elevations formed by the basioccipital, continuing
the pterygoid ridge backwards. The glenoid fossa (gf) is
a shallow, oval facet, on the inner and under surface of the
zygomatic process of the squamosal.

The periotic region of the skull differs much from that
of most Mammals. On the side of the base of the cranium
is a large recess, bounded below by the prominent edge of
the basioccipital on the inner side, by a projecting edge of
the exoccipital (paroccipital process) behind, by the base
of the zygomatic process of the squamosal externally, and
by a long curved process from the same bone in front, and
communicating with the cranial cavity above by an irregular
opening between the exoccipital and the alisphenoid. In
this recess lies a bone of singular shape which, having only
a ligamentous connection with the surrounding bones, is
easily separated from the rest of the cranium in maceration,
and is hence often wanted in specimens in museums. This
is the united tympanic and periotic, ankylosed in the adult,
but in young specimens still separable into its two com-
ponent parts.

The tympanic (Ty) is a hollow, bullate bone, broad,
rounded and bilobate behind, and pointed in front. It
is open above, the hinder part being, however, in relation
with the periotic. Through the anterior spout-like end the
Eustachian canal passes. At the upper border of the outer
side, rather behind the middle, is an irregular or somewhat
crescentic opening, bounded in front by a prominent lip,
this is the meatus auditorius externus, closed in the living
animal by the membrana tympani.

216 THE SKULL. [CHAP.

The periotic is a rounded, very dense bone, characterised
as usual by having on its inner or cerebral side the large
meatus auditorius internus, and on the surface turned
towards the tympanic cavity, the two fenestrae (ovalis and
rotunda). The tympanic and periotic bones are separated
along their inner margin by a narrow fissure, the "tympano-
periotic fissure " ; but they are united externally in front of
the external meatus auditorius, and more firmly posteriorly,
where a tongue-shaped process (Per) projects backwards
and outwards, fitting into a groove formed by the junction
of the squamosal and exoccipital, and which is the principal
point of attachment of the tympano-periotic bone to the
rest of the skull. This process resembles in its relations the
mastoid of ordinary Mammals, but in young Cetaceans it
may be seen to be composed of two nearly equal parts, in
close apposition with each, the inferior being derived from
the tympanic, and the superior from the periotic, so that
the latter alone can represent the "pars mastoidea " of
other Mammals.

The mandible (Fig. 65) consists of a pair of nearly straight
compressed rami, wide behind and gradually narrowing to
the symphysis (s), where they usually become ankylosed in
adult animals. The condylar articular surface (cd) is small
and looks almost directly backwards, being placed on the
hinder edge of the ramus. The coronoid process (cp) is
quite rudimentary. The angle is square and flat. The
entrance to the dental foramen on the inner side is ex-
tremely wide and infundibuliform.

The ossified portion of the hyoid in the adult Dolphin
consists of a large subcylindrical, slightly curved stylohyal (s/t)
on each side, and a flattened crescentic median bone, com-
posed of the ankylosed basihyal (b/i) and thyrohyals (t/i). The
stylohyal is connected above by a slender cartilaginous rod

xii.] CETACEA. 217

to a small ossified tympanohyal, which becomes ankylosed to
the periotic in the usual situation, close to the stylomastoid
foramen ; it has also a strong ligamentous attachment to
the prominent rough paroccipital process of the exoccipital.
Between the stylohyal and the basihyal are one or two dis-
tinct short cartilages articulated together by synovial joints,
one of which occasionally becomes ossified.

In many of the Delphinidic the rostral portion of the skull
is proportionately more elongated and compressed than in
the species just described ; notably so in Pontoporia, a South
American genus. In this animal the mandible has a very
long symphysial portion, the two rami being parallel and
ankylosed for more than half their length, and diverging
only in the posterior portion.

The Sousou, or Platanista, a Dolphin inhabiting the
rivers of South Asia, has also a remarkably elongated and
compressed rostrum and mandible, and the cranial portion
of the skull presents several structural peculiarities. The
orbit is extremely small, the temporal fossa large, and
the zygomatic processes of the squamosal are greatly
developed. From the outer edge of the ascending plates
of the maxilla;, which lie over the frontals, great crests of
bone, smooth externally, but reticulated and laminated on
their inner surface, rise upwards, and curving inwards, nearly
meet in the middle line, above the upper part of the face.

The PhyseteridiC, including the genera Ziphius, Hy-
peroodon, Physeter, and their allies, present several special
modifications of the skull. The bones of the face and
cranium, meeting at the vertex, are raised so as to form a
more or less elevated transverse prominence or crest behind
the anterior nares, generally curved forwards at its upper
edge. The bone which corresponds to the malar in other

218 THE SKULL. [CHAP.

Dolphins is usually divided into two, one of which may
represent the lacrymal. The pterygoid bones are thick,
produced backwards, meeting in the middle line for a
considerable space, concave on their outer side, but not
involuted to form an outer wall to the post-palatine air sinus.
In some of the Ziphiincz the rostrum is very dense, the
anterior prolongation of the mesethmoid being either
partially or completely ossified, and ankylosed with the
surrounding bones.

In Hypcroodon, the crest at the vertex is high and mas-
sive, being formed by the nasals, the ascending plates of the
premaxillas and maxillse, the frontals and supraoccipital.
Separated from this crest by a depression, there is on each
maxilla, at the commencement of the rostral portion of the
skull, a very thick and high longitudinal ridge, which attains
an extraordinary development in the old males of the com-
mon Northern species.

An easy transition from this cranium leads to that of
the great Sperm Whale or Cachalot (Physefer macrocephalus),
which of all Mammals is perhaps the most modified from
the ordinary type. The transverse vertical crest and the
longitudinal maxillary crests are united to form the walls
of a great semicircular basin, surmounting the whole of
the back part of the cranium, open only above and in
front. The bones composing this wall are the same as in
Hypcroodon, but excessively expanded and flattened. The
rostrum is broad at the base, gradually narrowing to the
front, and immensely elongated. The great supracranial
cavity lodges the oily substance which, when refined, is
known as spermaceti.

The skull of the Cachalot is remarkable for its want of
symmetry, especially in the region of the anterior narial
apertures, of which the left is very much larger than the

xii.] CETACEA. 219

right. In consequence of the small increase in the size of
the brain-cavity, compared with that of the external parts of
the head in these enormous animals, the foramina through
which the nerves pass out of the lateral parts of the base
of the skull, are long channels excavated through immense
bony masses. The petro-tympanic bone, which is scarcely
larger than that of some of the small Dolphins, is situated
at the bottom of such a channel, at the distance of fourteen
inches from the inner wall of the brain cavity. In the
general principle of their conformation, these bones do not
differ from those of the ordinary Dolphins, but the tongue-
shaped backward projection before described is greatly
elongated and laminated, being composed of a large num-
ber of distinct thin plates, only held together by their com-
mon attachment to the tympanic. These fit into grooves
between the squamosal and exoccipital, their extremities
appearing on the outer surface of the skull, and they serve
to attach the petro-tympanic more firmly to the cranium
than is the case in the other Toothed Whales.

The hyoid in Phyxeter and in the allied genus Kogia is
remarkable for the great breadth and flatness of the basi-
and the thyro-hyals, which, moreover, do not usually become
ankylosed, as in most Dolphins.

The cranium of the Whalebone Whales (sub-order Mysta-
coceti) never shows that deviation from bilateral symmetry
so frequent in the Toothed Whales. The cranial cavity-
has much the same general form, and the bones around are
disposed in a somewhat similar manner, but the parietals
meet at the top of the skull, although completely overlaid
and concealed externally by the great supraoccipitaL

The anterior nares are not directed upwards and back-
wards as in the Dolphins, but approach more in position to
those of the ordinary Mammalia, being arched over by the

220 THE SKULL. [CHAP.

frontals, which are of considerable antero-posterior thick
ness at this part (see Fig. 67, Fr), and also by moderately-
developed nasals (No), meeting by a flattened surface in
the middle line. The nares are still near the most elevated
part of the head, and the premaxillae and maxillae, with the
vomer and mesethmoid cartilage, are produced in front of
them into a long tapering rostrum, narrow, compressed, and
much arched in the Right Whales (JBalcetia) ; broader, de-
pressed, and nearly straight in the Rorquals (Balcenoptera).

An essential difference between the Whales and the
Dolphins is the presence in the former of an olfactory organ
of the same type as in other Mammals, though in a compara-
tively rudimentary condition. In the skull of an adult Green-
land Whale (Balana mysticetus), the olfactory fossa of the
cerebral cavity is eight and a-half inches in length, scarcely
more than half an inch high, and one and a-half inch
wide. It runs forward from the anterior part of the floor of
the cerebral fossa, through the great mass of bone formed by
the union of the frontal, mesethmoid and presphenoid. In
front it divides into two compartments, each somewhat oval
and dilated, with a concave floor about an inch in extent
in either direction, perforated with foramina. This floor is
the cribriform plate. In the hinder wall of the great narial
passage is a narrow vertical slit, twelve inches in length,
very near the middle line ; this is the opening of the
olfactory chamber of the nasal cavity, which is bounded
by the under surface of the cribriform plate above, by the
flat mesethmoid on the inner side, and has its outer wall
raised into several longitudinal elevations of very simple
character, representing the ethmoturbinal bones.

In the Rorquals (Balcenoptera) the olfactory fossa is less
elongated, the foramina of the cribriform plate larger and
more numerous, and the ethmoturbinals better developed.

XII.]

CETACEA.

221

The supraorbital processes of the frontals are very long
and narrow in the Right Whales, but broader in the Rorquals ;
they are not covered by plates from the maxillae, as in the
Dolphins. The orbit is small and completed below by a
small curved malar, quite different from that of the
Dolphins. There is a small wedge-shaped lacrymal inter-
posed between the antorbital processes of the frontal and
maxilla and the malar.

FIG. 67 —Section of the skull if a foclal Southern Right Whale (Baltrna austratis).
i\. /M/r prcmaxilla ; \a nasal : /•rfronlal ; fa parietal : SO cupmoccipital : OS
orbitosphcnoid ; . I-V alisphenoid ; Kx<) exoccipital ; Per penotic ; BO basi-
occipital : Ty tympanic ; US basisphenoid ; Sy glenoid articular surface of suua-
mosal ; XV ptcryguid ; /V palatine; f'S presphenoid ; I'a vomer; /V.r maxilla:
<•/ coronoid process uf mandible; cd condyle ; dg dental groove ; mg remains of
groove which lodged Mcckel's cartilage. No part of the mcscthmoid is ossified.

The palate is long and narrow, with a strong keel or
ridge in the middle line. The surface on each side, sloping
upwards and outwards, is perforated by many large foramina
to permit the passage of blood-vessels and nerves to the
matrix of the baleen, or " whalebone," which covers it in
the living animal. It is chiefly formed by the maxilla,

222 THE SKULL. [CHAP.

behind which are large palatines and very small and widely
separated pterygoids.

The zygomatic process of the squamosal is an immense
trihedral pillar in Balcena, having the large shallow glenoid
fossa on its under surface removed considerably from the
middle of the cranium, so as to give sufficient width to the
hinder part of the capacious mouth. The periotic and
tympanic are formed much on the same principle as in the
other sub-order, and in adult animals are completely excluded
by a considerable distance from the cranial cavity, owing to
the thickness of its walls. Instead of the small flattened
tongue-shaped process projecting backwards from these bones,
there is a long pyramidal tenon-like process, which fits into
a groove in the squamosal and appears on the external sur-
face of the skull like, though more solid than, that of the
Cachalot. In addition to this another process projects out-
wards and backwards, and the two together hold the bones
much more firmly in their place than in the Toothed Whales.
The tympanohyal is a large conical bony mass, with a
truncated base, with which the stylohyal is connected, and
firmly ankylosed by its apex to the periotic.

The mandible differs much from that of the Toothed
Whales. The two rami of which it is composed are not com-
pressed and straight, but rounded and arched outwards, and
never have extensive, flat, opposed symphysial surfaces, but,
curving towards each other, meet at an angle in front, where
they are held together by strong bands of fibrous tissue.

The hyoid arch is formed essentially on the same plan as
in the other Cetacea. The basihyal has a pair of processes
placed side by side on its front edge, to which the anterior
cornua are attached ; the hinder edge is excavated. In
Balocna the thyrohyals are cylindrical, and thicker towards
their free extremities. In Balanoptera musculus they are

xii.] SIKENIA. 223

cylindrical and tapering, in B. rostrata, flat and pointed
externally. They always ankylose with the basihyaL

Order SIRENIA. — The animals belonging to this order,
restricted at the present time to only two genera, which were
formerly, but quite erroneously, included among the Cetacea,
have skulls constructed on a very peculiar type, though with
some affinities both to the Ungulata and the Proboscidea.
Many of the special modifications are adaptations to their
aquatic mode of life, and it is in these alone that they
present any resemblances to the Cetacea.

The skull of the African Manatee (Manatus senegalensis,
Fig. 68), which may be taken as a type of the order, is remark-
able for the massiveness and density of structure of the bones
of which it is formed. There are no air sinuses in any part,
and most of the bones when cut through appear as hard and
solid as ivory. This character is not peculiar to the skull,
but shared with it by the ribs, and other bones, and must
add much to the general specific gravity of this slow-moving
animal, and aid in keeping it to the bottom of the shallow
water in which it dwells, while feeding on fuci and other
aquatic vegetables.

The cerebral cavity is very different from that of the
Cetacea, being small as compared with the size of the
animal, rather elongated and laterally compressed, truncated
at each end, and with the upper surface flattened. The
cerebellar fossa is large, and altogether behind the cerebral ;
the olfactory fossa is distinct, but small and narrow, bounded
on the inner side by a strongly-developed " crista galli " from
the mesethmoid. The foramen magnum is of great size ; its
plane looks backwards and downwards. The supraoccipital
(SO) is inclined forwards, but does not extend beyond
the ridge bounding the occipital region ; the roof of the

224

THE SKULL.

[CHAP.

cerebral fossa of the cranial cavity being formed by the pari-
etals (Pa). The upper surface of the skull is very narrow,
and flat or slightly arched in the longitudinal direction ; its

FIG. 68.— Section of the skull of an African Manatee (Manatiis senegalensis). \.
PMx premaxilla; Vo vomer ; MX maxilla; Fr frontal; ET ethnioturbinal :
M E mesethmoid : Fr frontal ; Pa parietal ; Sq squamosal ; SO supraoccipital ;
E.rO exoccipital ; Per periotic ; BO basioccipital ; 'J y tympanic ; AS alisphenoid ;
US basisphenoid ; /'.9 prcsphenoid ; Pt pterygoid ; PI palatine ; Vl/.r maxilla ;
cp coronoid process of mandible ; cd condyle : a angle ; ^ symphysis ; sh stylo-
hyal ; bh basihyal ; tk thyrohyal.

sides, which are parallel for a considerable distance, join
at a right angle the vertical inner wall of the great temporal
fossa. The squamosal has an extremely massive and long

xii.] SIXENIA. 22$

zygomatic process, flattened on the outer surface, and
posteriorly it sends down a strong triangular post-tympanic
process, articulating with a rough projecting edge of the
exoccipital. Above this, between the squamosal, supra-
occipital, and exoccipital, is a considerable vacuity in the
cranial wall, partly filled by the periotic (Per). The lower
vacuity, between the exoccipital and alisphenoid, common
to all skulls, is of immense extent.

The frontals (Fr) are narrow, and run backwards between
the parietals to the upper part of the cerebral fossa of the
brain cavity, and forwards a short distance over the nasal
cavities ; each is produced anteriorly into a long narrow
process, inclining outwards and downwards, between the
temporal fossa behind, and the great anterior narial openings
in front, forming the roof of the orbit. This cavity has a
very prominent margin, especially below and in front, where
it is formed by the very largely developed malar. This bone
sends upwards a conspicuous postorbital process, which
nearly (in some cases completely) meets that of the frontal,
and then is continued below the zygomatic process of the
squamosal as far as the wide shallow glenoid fossa, and
sends down from its middle a broad flattened process with a
thickened and rough inferior border. There is a very small
scalelike and imperforate lacrymal in the usual situation at
the anterior and inner angle of the orbit. The antorbital
foramen of the maxilla is very large.

One of the most peculiar features of the upper surface of
the face is derived from the position of the anterior nares,
which is a further modification of that met with in the Tapirs
among the Ungulata, and presents some approach to that
so characteristic of the Cetacea. Taken together they form
a large lozenge-shaped aperture, which extends backwards
considerably behind the orbits. Their sides are formed by

Q

226 THE SKULL. [CHAP.

the ascending processes of the premaxillse below, and by
the supraorbital processes of the frontals above, no trace of
nasals being found in most skulls, though these bones are
occasionally present in a most rudimentary condition attached
to the edge of the frontals, far away from the middle line,
a condition quite unique among the Mammalia, or only
approached in some of the Dolphins. In the floor of the
great narial opening is seen the vomer ( Vo], of very delicate
structure, and posteriorly the ossified portion of the mes-
ethmoid (ME) of considerable vertical extent. The olfac-
tory chamber of the nasal cavity is greatly compressed from
side to side, and contains a series of simple, longitudinally
placed ethmoturbinals, of which the upper one is very much
the largest. There are no maxilloturbinals in any skulls
which I have examined.

In front of the narial opening the face is prolonged into
a narrow rostrum, formed by the premaxillce, supported
below and at the sides by the maxillae. The under surface
of this is very rugose, and in life supports a horny plate.
There is a large, oval, single, median anterior palatine
foramen. The palate is long and narrow between the two
parallel rows of numerous molar teeth. It does not extend
beyond the last of these, and is formed almost entirely by
the maxillae, the horizontal plates of the palate bones
being very narrow. Behind each row of teeth is a massive
descending rough process, formed by the union of the
palatine, pterygoid plate of the alisphenoid, and true
pterygoid. Posteriorly this has a longitudinal groove cor-
responding to the pterygoid fossa. Behind this the base
of the skull contracts in width, leaving a large opening on
each side of the basioccipital. between the alisphenoid in
front and the exoccipital behind, and only partially filled by
the tympanic and periotic.

xil.] SIREN/A. 227

The two last-named bones are ankylosed together, but not
to any of the other bones of the skull, and though freely
movable in the dried skull, they are retained in their place
by the overhanging process of the squamosal.

The tympanic (Ty) consists of a large and very solid half-
ring, with its lower margin considerably thickened and
produced downwards ; but not forming any bulla, or any
tubular meatus. It is only attached to the periotic by its
extremities, and close to the inner side of its posterior
attachment is a well-marked tympanohyal ankylosed to the
periotic.

The periotic (Per) is large and rounded externally. It
forms a very considerable part of the inner wall of the
cranium. Besides the portion containing the organ of hear-
ing, it has a large solid upper part of somewhat kidney
shape, lying in a groove in the squamosal (Sq). This solid
part has a large anterior prominence, to which the anterior
limb of the tympanic ring is ankylosed, and a smaller rounded
posterior projection, corresponding with the mastoid of other
Mammals, and mentioned before as appearing on the ex-
ternal surface of the skull, in the vacuity between the supra-
occipital, exoccipital, and squamosal.

The foramina at the base of the skull are very few and
simple, as nearly all the nerves appear to pass out only by
the rather small sphenoidal fissure, and by the great confluent
median and posterior foramina lacera. There is a small
optic foramen passing through the middle of the orbito-
sphenoid, but the alisphenoid is imperforate, and even the
condylar foramen in the exoccipital for the hypoglossal
nerve, so constant in all Mammals (except the Elephant), is
represented by a groove (in some instances with a narrow
bridge across it) on the anterior edge of the bone. There
is no distinct carotid canal.

The mandible is exceedingly different from that of the
Q 2

228 THE SKULL. [CHAP. xn.

Cetacea, and is formed of the same dense heavy bone as the
rest of the skull. The rami are firmly united by a symphysis
(s) of moderate extent in front, and diverge widely behind.
The posterior border is of considerable vertical depth, the
condyle (cd], with its obliquely placed, oval, convex arti-
cular surface, being raised high above the horizontal alveolar
border. The coronoid process (cp) is large and directed for-
wards. The angle (a) is well marked, thickened, and some-
what inflexed, but does not form a distinct process. The
lower border of the ramus is very thick, rounded from
side to side, and concave from before backwards. The
symphysial portion is compressed laterally, but its upper
surface forms a somewhat expanded, rugose surface, concave
in the middle line, to which a horny plate is attached in the
living animal.

The anterior arch of the hyoid has a single, slender,
slightly-curved bone (stylohyal), three inches long, cylindrical
at its upper end, and laterally compressed below, attached
above by a broad, short ligament, chiefly to the exoccipital,
but also to the squamosal and tympanic. The basihyal
is a broad, flat, reniform plate, and the thyrohyals are not
ossified.

In the other existing Sirenian, the Dugong (Halicore}, from
the Indian Seas, the skull resembles that of the Manatee in
its essential characters, especially the form of the brain-case,
the condition of the tympano-periotic bones, and the form
and situation of the anterior nares ; but it differs mainly in
the great development of the premaxillary bones, which curve
downwards in front, and lodge large descending tusks The
deep, compressed symphysial portion of the mandible is
bent down in a corresponding manner. The zygoma is less
massive, the orbit is not closed behind, and the lacrymal
bone is more developed. The nasals are absent or quite
rudimentary.

CHAFFER XIII.

THE SKULL IN THE EDENTATA, MARSUPIALIA, AND
MOXOTREMATA.

Order EDENTATA. — The different families of this hetero-
geneous group present some remarkable variations in their
cranial characters.

One of the most extremely modified forms is the Great
Anteater (Myrntecc'phaga jubata, Fig. 69). The whole skull
is very greatly elongated and narrow, and its upper surface
smooth and cylindriform. The occipital plane slopes upwards
and forwards. The parietals are narrow, but the frontals much
elongated. The olfactory fossa of the cerebral cavity is very
large ; the cribriform plate greatly expanded, and the ethmo-
turbinals much developed, and consisting of very numerous,
delicate lamelke. Anteriorly, the face is produced into a
very long, tubular rostrum, rounded above and flattened
below, and with terminal nares. This rostrum is composed
of the mesethmoid, ossified for more than half its length,
the vomer, the maxillae, and the long and narrow nasal
bones, the premaxillae (PAfx) being extremely short and
confined to the margin of the anterior nares. There are no
teeth in either jaw. The zygomatic arch is incomplete, the
styliform malar (Afa) only articulating with the maxilla in

THE SKULL.

[CHAP.

FIG. i

of

PALrl

69. — Under-surface of the cranium
the Great Anteater (Myrmecophaga

front, and not reaching the
very short zygomatic process
of the squamosal (Sq]. The
lacrymals (Z) are distinct, and
have a large perforation in
front of the margin of the
orbit. There are no postor-
bital processes to the frontals,
or any other demarcation
between the orbits and the
temporal fossae.

The palate is extremely
elongated, and produced back-
wards as far as the level of
the external auditory meatus
by the meeting in the middle
line of the largely-developed
pterygoids (Pf). The glenoid
fossa is a shallow oval facet,
with its long diameter from
before backwards.

The periotic, tympanic, and
squamosal are ankylosed to-
gether. A small mastoid
portion appears on the outer
side of the skull, forming a
roughened surface between the
squamosal and the exoccipital.
The tympanic (Ty] is some-
what triangular in form,
slightly bullate, and not pro-
longed into an auditory meatu*.
of the tympanic:

xili.] EDENTATA. 231

cavity, and freely communicating with it, is a considerable
air sinus, formed between the pterygoid (Pf) and the ali-
sphenoid (AS), and causing an oval prominence in the side
of the palate.

In another species of the same family, Tamandua tetra-
dactyla, there is a second similar but smaller sinus anterior
to this, in the side of the palatine bone.

The mandible is very long and slender, with an exceed-
ingly short symphysis, no distinct coronoid process, and
a slightly elevated, elongated, flattened, condylar articular
surface.

The anterior cornu of the hyoid is very long and slender.
Its proximal end is ligamentous, and its distal portion con-
tains three distinct ossifications. The thyrohyals become
united by bone to the very narrow basihyal.

The skull of the little Tree Anteater (Cycloturns didac
tylus) besides being shorter, and much arched in the longi-
tudinal direction, differs mainly from that of Myrmecophaga
in not having the long canal of the posterior nares closed
by bone below, as neither the pterygoids nor the greater
part of the palatines meet in the middle line. The
tympanic is more bullate. The mandible has a pro-
minent, narrow, recurved coronoid, and a well-developed
angular process ; it is strongly curved downwards in front.

In the Armadillos of the restricted genus Dasyfits, in-
cluding D. sexcinctus, rillosus, and minutus, the cranial
portion of the skull is broad and depressed ; the facial
portion triangular, pointed in front, and much depressed.
The anterior narial orifice is small, terminal, and directed
forwards and downwards. There is a completely ossified
tympanic bulla, ankylosed with the rest of the skull, per-
forated on the inner side by the carotid canal, and con-
tinued externally into an elongated bony meatus auditorius,

232 THE SKULL. [CHAP.

with its aperture directed upwards and backwards. The
zygoma is complete. The pterygoids are small, and send
no horizontal plates inwards to complete the bony palate, as
in the Anteater. The mandible has a well-marked ascending
posterior portion, supporting a transversely extended con-
dyle, and a high, slender coronoid process.

In all the other genera of Armadillos, Chlamydophorus
excepted, the tympanic is a mere half-ring, loosely connected
with the surrounding bones.

The hyoid arch is strongly ossified. The anterior cornu
consists of three bones. The thyrohyals ankylose with the
basihyal.

In the Scaly Anteaters or Pangolins (genus Manis), the
skull is somewhat in the form of an elongated cone, with
the small end turned forwards, and very smooth and free
from crests and ridges. The occipital plane slopes upwards
and forwards. There is no distinction between the orbit and
the temporal fossa, which together form a small oval depres-
sion near the middle of the side of the skull. There are
short zygomatic processes on the maxilla and the squa-
mosal, but the arch is incomplete in most species, owing to
the absence of the malar. There is likewise no distinct
lacrymal bone. The plane of the anterior narial aperture
looks forwards and upwards. The premaxilla is produced
along the side of the nasals towards, but not reaching, the
frontals. The palate is long and narrow. The pterygoids
extend backwards as far as the tympanics, but do not meet
in the middle line below. The tympanic is ankylosed to
the surrounding bones, and more or less bullate, but not
produced into a tubular auditory meatus. The hinder
part of the squamosal is often dilated with air-cells,
forming a rounded prominence at the outer posterior angle
of the skull.

xni.] EDENTATA. 233

The rami of the mandible are edentulous, very slender
and straight, without any angle or coronoid process. From
near the anterior extremity of the upper edge a sharp conical
tooth-like process projects upwards and outwards. The
condyle is a slightly expanded flattened surface, not raised
above the level of the rest of the ramus.

In the Cape Anteater (Orycteropus) the skull is moderately
elongated and dilated in front of the orbits. The facial por-
tion is subcylindrical and slightly tapering. The lacrymal
forms a considerable part of the side of the face. The
zygoma is complete and slender. There is a small post-
orbital process. The premaxillae are short and widely
separated from the frontals. The palate ends posteriorly in
the thickened transverse border of the palatines, and is not
continued back by the pterygoids. The tympanic is annular
and not ankylosed to the surrounding bones.

The mandible is slender anteriorly, but rises high pos-
teriorly, with a slender recurved coronoid, and an ascending
pointed process on the hinder edge below the condyle,
which is small, oval, and looks forwards as much as up-
wards.

The hyoid arch is completely ossified. The basihyal
is a thin bar, narrow in the middle. The thyrohyals are
not ankylosed to it The ceratohyals are thick. There is
a small (apparently epiphysial) ossification between the
epihyal and the stylohynl.

The Three-toed Sloths (genus Bradypus) have a high
compressed skull, and an extremely short face. The cranial
cavity is oblong, and rather high and compressed. There is
no fossa on the periotic for the flocculus. The olfactory
fossae are large. The plane of the occiput is vertical, or
sloping slightly forwards and upwards. The frontal region

234 THE SKULL. [CHAP.

is dilated with air sinuses. There is a small postorbital
process. The lacrymal is very small, and the canal is
external to the margin of the orbit. The malar is attached
to the frontal, lacrymal and maxilla in front, curves down-
wards and outwards, and then divides into a descending and
a high ascending branch ; but neither of them join the
straight zygomatic process of the squamosal. The nasals arc
short and wide. The anterior nares are nearly vertical, or
rather inclining downwards. The premaxiliee are exceedingly
rudimentary, only the palatal portion being present, without
any ascending process ; they unite with each other across
the middle line, but not with the maxillae, hence they are
generally lost in macerated skulls. The palate is narrow,
especially posteriorly, and not produced behind the molar
teeth. The pterygoids form large plates with prominent
rounded borders, compressed in some, and inflated in
other species. The glenoid fossa is narrow from side to side.
The tympanic, squamosal, and periotic are ankylosed
together. The former forms a considerable bulla, but no
tubular meatus. There are large supratympanic air sinuses,
and a well-marked ossified tympanohyal.

The mandible has a comparatively high horizontal por-
tion, rounded in front with a very small median triangular
process at the upper border. The coronoid process is high
and slender. The condyle is small ; its articular surface
is convex from side to side, short and nearly straight
from before backwards. The angle forms a broad com-
pressed posterior projection, with a slightly incurved lower
border.

The stylohyals are large, compressed, and curved, with a
prominent posterior process near their upper end. The
basihyal is small, and ankylosed with the thyrohyals, so that
they form together a V-shaped bone.

xiii.] EDENTATA— MARSUPIAL1A. 235

The skull of the Two-toed Sloth (Cholcepus didactylus),
though generally similar to the last, presents in some points
marked deviations from it. Even in aged specimens, in
which almost all the sutures are obliterated, the tympanic
is a mere ring, incomplete at the upper margin, and but
slightly connected with the other bones around. The
premaxillae are more developed, and become ultimately
ankylosed with the maxillae. The pterygoids are much
smaller, but sometimes are bullate.

The upper margin of the mandible is produced anteriorly
into a spout-like process. The condyle is scarcely above
the level of the molar teeth, and is wide from side to side.
The angular projection is smaller and thicker.

The hyoid (in an old specimen) has a strongly ossified
anterior arch, consisting of two bones of nearly equal length,
the proximal one with a stout-rounded process projecting
backwards and outwards from near its upper end. The
second is bent at a right angle near its lower end, and may
result from the ossification of two elements. The basi- and
thyro-hyals are ankylosed to form a wide U-shaped bone.

Order MAKSUPIALIA. — -The skull of the large carnivorous
Marsupial, the Thylacine (Thylacinuscynocephalus), resembles
so closely that of a Dog in its general aspect, that it will be
well to commence an account of the peculiarities of the
crania of Marsupials generally by comparing these two
skulls.

It will be seen by the section (Fig. 70) that the brain cavity
of the Thylacine is very much smaller than that of the Dog
(Fig. 46, p. 117) in relation to the size of the rest of the
cranium, or to that of the whole animal, a sign of great in-
feriority of organisation. This diminution affects chiefly the
cerebral fossa ; the cerebellar fossa is nearly equal in size,
but it is placed more directly behind the cerebral, and is

236

THE SKULL.

[CHAP.

not in the least overlapped by it, as in the Dog. The
occipital plane is vertical, or even inclining forwards above.
The tentorial plane is nearly horizontal. The olfactory
fossa, though smaller in vertical extent than that of the Dog,
is more produced anteriorly. Thus in form, as well as in
relative size, the cerebral cavity is far more reptilian than
that of the Dog. The basicranial axis is very straight, and

FK;. 70, — Section of the skull of the Thylacine (TJiylacinus cynocephalus), \.
MT maxilloturbinal ; ET ethmoturbinal ; ME ossified portion of mesethmoid ;
/•> frontal ; Pa. parietal ; SO supraoccipital ; EjcO cxoccipital ; Per periotic ;
BO basioccipital ; S<] squamosal ; AS alisphenoid ; TiS basisphenoid : OS orbito-
sphenoid ; 1'S presphenoid : Pt pterygoid ; /V palatine; f'fvomer; M.\ maxilla ;
PMx premaxilla; ai condyle of mandible ; a angular process.

is continued forwards in the same line by the basifacial
axis. The pituitary fossa forms no distinct impression, and
there are no posterior clinoid processes. The ossified
portion of the mesethmoid (AfE) is extensive, and termi-
nates anteriorly in a nearly vertical line. The vomer ( Vo)
is very shallow from above downwards. The turbinal

xiii.] MARSUPIALIA, 237

bones resemble generally in their extent and disposition
those of the Dog.

Externally the conformation of the zygomata, temporal
fossae, orbits, maxillae, premaxillae, and nasals are strikingly
similar to those of the Dog ; but the lacrymal bone of the
Thylacine is larger both within and without the orbit, and
it has one perforation within, and either one or two just
external to the margin of the orbit. The palate has a pair
of large oval vacuities between the molar teeth. The ptery-
goid plates are very thin. The glenoid fossa is rather more
expanded from before backwards than in the Dog, and the
malar extends so far back beneath the zygomatic process of
the squamosal as to form the outer edge of the glenoid cavity.
The postglenoid and paroccipital processes are developed
much as in the dog ; the former has rather greater lateral
extent. A great difference is seen in the condition of the
tympanic, which in the Thylacine is quite rudimentary, forms
no bulla, and is not ankylosed to the other cranial bones,
so that in the dried skull it is nearly always detached. On
the other hand, the hinder part of the alisphenoid is dilated
into an oval thin-walled capsule, which is connected with
the front of the tympanic cavity. The periotic is not
ankylosed to the squamosal, has a very large floccular fossa
within, and a mastoid portion forming a long, narrow strip
visible in the outer side of the occipital surface of the skull,
between the squamosal and the exoccipital, almost exactly
as in the Dog. The exoccipital is perforated by the con-
dylar foramen ; but the carotid foramen, instead of passing
through the inner edge of the tympanic bulla, perforates
the basisphenoid, passing very obliquely forwards and in-
wards. The large alisphenoid is pierced by the fora-
men ovale near its posterior margin, and by the foramen
rotundum near the front. The orbitosphenoid is very small,

238 THE SKULL. [CHAP.

and not perforated, the optic nerve passing out through the
sphenoidal fissure.

The ascending ramus of the mandible is less elevated than
that of the Dog, the condyle being almost on the same level
as the molar teeth. The coronoid process has a more back-
ward inclination. The masseteric fossa has a powerful,
externally projecting lower border, and the angular process
is flattened from above downwards, and inclined consider-
ably inwards.

The hyoid (Fig. 71) is constructed on a totally different
type from that of the Dog. It consists of a small flat lozenge-
shaped basihyal (/>//), surmounted by flattened, triangular,

i it

Fi<;. 71. — Upper surface of hyoid of Thylacine (nat. size), bh basihyal ; ch ceratohyai
(anterior cornu); th thyrohyal (posterior cornu).

imperfectly ossified ceratohyals (ch}, partially ankylosed to
the basihyal, and without any other ossifications in the
anterior cornua. The thyrohyals (///) are tolerably long
flattened bars, meeting in the middle line at their attachment
to the basihyal, and with their free, or laryngeal, extremities
expanded, but still cartilaginous in the perfectly adult animal
from which the above figure was taken.

All the other animals of the sub -class which contains the
single order Marsupialia, however their skulls may differ in

xiii.] MARSUPIAL1A. 239

general appearance from that of the Thylacine, agree with it
in the following important particulars :—

1. The brain cavity is small, with the cerebella fossa
entirely behind, and the olfactory fossa entirely in front of
the cerebral fossa. There are, however, degrees in this res-
pect, the Kangaroos representing one extreme, with large,
more vaulted cerebral fossa, and the Opossums and Dasyures
the other.

2. There is no distinct pituitary fossa, and the clinoid
processes are obsolete.

3. The ossification of the mesethmoid is extensive, and
has an abrupt, nearly vertical, anterior termination.

4. The nasal bones are large, and the anterior nares more
or less terminal.

5. The zygoma is complete, but the orbit has not a perfect
posterior boundary.

6. The malar is large, reaches the lacrymal anteriorly,
and extends posteriorly beneath the zygomatic process of
the squamosal, to form part of the outer wall of the glenoid
fossa.

7. The perforation in the lacrymal is usually upon, and
frequently external to, the anterior boundary of the orbit.

8. The ascending processes of the premaxillae never quite
reach the frontals.

9. The palate has often, but not always, large vacuities
near its posterior margin.

10. The pterygoids are always small and lamelliform.

11. The alisphenoids are more or less dilated, and form
the anterior wall of the tympanic cavity, which is often quite
open below in the dried skull. It may be noted as a special
peculiarity in the Kangaroos, that the alisphenoid extends
backwards beneath the tympanic cavity to join the long
paroccipital process of the exoccipital. In the larger mem-

240

THE SKULL.

[CHAP.

bers of the group it can scarcely be said to form a distinct
bulla, but in some of the Hypsiprymni (Rat Kangaroos) it is
immensely expanded. In the Koala (Phascolarctos)^ the
alisphenoid bulla is very large, elongated vertically and
compressed, having a very similar appearance in fact to the
tympanic bulla of the Pig.

12. The tympanic is small, simple, and annular in some ;
in others it forms a short external auditory meatus, but
it is never ankylosed to any of the other bones of the
cranium.

FIG. 72. — Upper surface of hyoicl oi
Wombat (fhascolomys latifrons). bh
basihyal ; fh ceratohyal ; sh stylohyal ;
tk thyrohyal.

K;. 73. — Hyoid of Kangaroo (Alacrn-
J>us). bh basihyal ; ch ceratohyal ; th
thyrohyal.

13. The periotic sends backwards a distinct mastoid, which
appears as a narrow strip of bone of considerable vertical
extent, between the squarnosal and exoccipital, on the side
of the occipital region of the skull.

14. There are almost always conspicuous paroccipita-1
processes.

15. The internal carotid artery perforates the basi-
sphenoid.

1 6. The optic foramen is confluent with the sphenoidal
fissure.

17. The mandible has (Tarsipes excepted) an inverted
border to the angle.

xiii.] MONOTREMATA. 241

1 8. The hyoid has a small, more or less lozenge-shaped
basihyal, broad ceratohyals, the remainder of the anterior
cornu usually unossified, and stout somewhat compressed
thyrohyals.

Order MONOTREMATA. — Both the animals of this group
present very singular modifications of the cranium.

The cerebral cavity, unlike that of the lower Marsupialia
or the Reptiles, with which they have so many structural
affinities, is large and hemispherical, flattened below and
arched above, and about as broad as long. ' The broad cribri-
form plate of the ethmoid is nearly horizontal. The walls
are very thin, and smoothly rounded externally, and the
sutures become completely obliterated in adult skulls so that
it is very difficult to trace out the boundaries of the com-
ponent bones. In both species, the broad occipital region
slopes upwards and forwards, and the face is long and much
depressed, though of very different shape in each.

In the Echidna (Fig. 74) the squamosal is large and very
compressed, the zygomatic process arising very far forward ;
the slender hori/ontal zygoma being completed by a styliform
malar, confluent with the maxilla. The face is produced
into a long tapering rostrum, rounded above from side to
side, and concave below in the same direction. The an-
terior nares form an oval opening on the upper surface near
the apex, bounded entirely by the premaxillaj, for the nasals
do not appear to reach so far forwards. The alveolar borders
are narrow and rounded, without trace of teeth. The palate
is produced backwards, by very large palatine bones (/*/),
considerably beyond the glenoid fossa. The narial canals
have very little extent vertically, but the true olfactory
chambers are large, and provided with complex turbinals,
which, in accordance with the horizontal position of the
cribriform plate, are mostly placed vertically.

242

THE SKULL.

[CHAP.

The pterygoids (Pt] are flattened, horizontal, oval plates,
attached to the obliquely truncated postero -external extremi-
ties of the palatines, and form part of the floor and the inner
wall of the tympanic cavity, an arrangement not met with in
any other Mammal. The tympanic (Ty) is a very slender

ring, incomplete for a small space
at the upper and outer end, and
does not become ankylosed to
the periotic. The latter (Per) is
large, has no fossa for the floc-
culus, sends out a large expansion
(pterotic), forming a portion of
the cranial wall between the
squamosal, parietal, and occipital,
the lower and hinder part at least
of which corresponds with the
mastoid portion.

Each ramus of the mandible is
a mere slender style, without any
ascending portion, and with but
rudiments of coronoid process
and angle. The condyle is very

FIG. 74,-Under surface of cranium Small, elongated from before
of Echidna (Echidna aculcata), \. K.lrl,iv'ird<; nnd vr>rv mrrmv

BO basioccipitai; ExO exocci- Dackwarob, ana vtry narrow .

The hyoid (Fig. 75) has a well-
ossified transversely extended,
flattened and arched (with the
concavity forwards) basihyal (bJi). The anterior cornu has
only two ossifications (eh and ch\ apparently the epi- and
cerato-hyal, as the upper one has a long ligamentous con-
nection with the cranium in the situation of the stylohyal.
There are broad, flattened, curved thyrohyals (tli) expanded
at their laryngeal extremities.

pital ; Per periotic ; m malleus
Sq squamosal ; Ty tympanic ; Pt
pterygoid ; /'/palatine ; MX max-
illa ; PMx premaxilla.

XML] MONOTREMATA.

243

In the Ornithorhynchus the brain case is smaller than in
the Echidna, and rather more depressed ; very broad behind
and narrowing anteriorly. The olfactory fossa is compara-
tively small. There are well-marked posterior clinoid
processes. The falx cerebri is largely ossified, forming a
strong median partition to the upper part of the cerebral
cavity. The zygoma is compressed, and of considerable
vertical depth, and sends up a well-marked postorbital
process ; its hinder root arises very far back on the
cranium.

The glenoid fossa is wide and concave transversely. The
zygomatic process of the maxilla is widened inferiorly into

Fir.. 75. — Lower surface of hyoid of Echidna (Echidna acttleata). th epihyal;
ck ceratohyal ; /•/; basihyal ; th ihyrohyal.

an oblong, concave, roughened surface for the attachment of
the horny plate, which takes the place of the molar teeth.

The face is broad and much flattened. It runs out
anteriorly into two diverging processes, each formed by the
premaxilla, supported by a pointed process of the nasal on
the inner and of the maxilla on the outer side. These bend
towards each other at their extremities, but do not meet in
the middle line. They support the partly horny, partly
membranous beak, which fills up the space between them,
and extends considerably on each side and in front. There
is a distinct median dumb-bell-shaped ossification in the

R 2

244 THE SKULL. [CHAP. xm.

triangular interval between the diverging premaxillary bars,
placed in front of the anterior extremity of the mesethmoid
cartilage, on the palatal aspect of the jaw. This bone is
not the homologue of the so-called prenasal of the Pig, but
" it corresponds with that part of the intermaxilla, which lies
between the incisive canal and the mesial palatal suture." :
The infraorbital foramen is very large, corresponding to the
large size of the nerves distributed to the sensitive sides of
the beak. The periotic has a wide and deep floccular fossa.
The mandible has, rather behind the middle of each ramus,
an oblong expansion for a horny tooth, corresponding to that
on the maxilla. Behind this it curves gradually upwards to
the expanded and transversely extended articular surface.
There is no distinct angle, the coronoid process is small and
directed much inwards, and on the external surface there is
a very deep masseteric fossa. Anteriorly the rami of the
mandible have a very slight symphysial connection, in front
of which their expanded, flattened terminations again diverge
from each other. The apertures for the entrance and for
the exit of the branches of the inferior dental nerve are
remarkably large.

1 W. Turner, " The dumb-bell-shaped Bone in the Palate of Ornitho-
rhynchus compared with the prenasal Bone of the Pig" (Journ. Anat.
Phys. xix. 1885, p. 214). P. Albrecht, " Sur la Fente Maxillaire et let.
quartre Os Intermaxillaires de 1'Ornithorynque. " Bruxelles, 1883.

CHAPTER XIV.

THE SHOULDER GIRDLE.

HAVING finished the consideration of the trunk and
skull we now turn to that of the two pairs of limbs, anterior
and posterior.

The anterior limb is present, and fully developed, in all
Mammals, being composed of a shoulder girdle and three
divisions belonging to the limb proper, viz. the upper arm
or brachium, the fore-arm or antibrachium, and the hand or
manus.

The SHOULDER GIRDLE in the large majority of Mammals
is in a comparatively rudimentary, or rather modified, con-
dition. Its true structure and its relations to the pelvic
girdle can only be understood by a reference to its condition
in the lower vertebrates.1

Each side of the girdle consists primitively of a curved
rod of cartilage, placed vertically (in the horizontal position
of the body), the upper or dorsal end being free, the inner
side lying upon, though not united with, some of the anterior
thoracic vertebrae or ribs, and the inferior or ventral end
being attached to the side of the presternum.

1 On this subject see W. K. Parker's valuable work before cited, and
also Gegenbaur's " Untersuchungen zur vergleichenden Anatomic," 2tes
Heft, 1865.

245 THE SHOULDER GIRDLE. [CHAP.

Near, or rather below, the middle of the outer surface of
this rod is a more or less cup-shaped depression, the glenoid
cavity, to which the head of the humerus, or bone of the
upper arm, is articulated. The whole rod is separated at
this spot into two divisions, which ossify from separate
nuclei. The upper or dorsal division is the scapula, the
lower or ventral division is the coracoid.

In all Mammals above the Ornithodelphia the greater part
of the coracoid is aborted, but a portion of its upper ex-
tremity always remains attached to the scapula as a process,
or sometimes as a most inconspicuous nodule, and occa-
sionally rudiments of the lower end are found attached to
the sternum. The scapula, on the other hand, is always
greatly developed.

A supplementary bone, developed in a different manner,
being, at least in the greater part of its extent, ossified from
membrane,1 frequently forms an anterior bar, in front of the
coracoid, passing between the scapula and the anterior end
of the presternum : this constitutes the clavicle. It is
often rudimentary, and very frequently entirely absent, in
Mammals.

Though the scapula may be considered as essentially an
elongated rod or bar of bone (a condition most nearly re_
tained in the Mole), it usually has three projecting plates
or ridges arranged around its longitudinal axis, and three
surfaces or fossae bounded by these, the variations in the
extent and form of which give rise to the principal diversities
in the form of this bone in different Mammals.

In the most usual position of the scapula (see Fig. 76),
one of these plates (of] projects forwards, this is the

1 When it has a cartilaginous basis (as has been described by
Ge^enbaur in Man) this is not a portion of the true primitive shoulder
girdle.

XIV.]

GENERAL CHARACTERS.

247

prascapula of Parker, and its edge constitutes the anterior
border (cb) of the scapula ; another (//) projects backwards,
constituting \hepostscapula, and its edge is the posterior border
(gb) ; a third projects outwards, constituting the mesoscapula
of Parker, called more commonly the spine (s). The first-
named border (cb) terminates below by joining the coracoid,
and hence, to avoid the inconvenience of a term which is
only expressive when the bone is in a particular position, it

.-'•

FIG. 76.— Right scapula of Dog (Cam's familiaris), \. pf postscapular fossa ; aj
pres«MpuI.tr fossa ; gb glcnoid or posterior border ; cb coracoid or anterior border :
s spine ; a acromion ; gc glcnoid cavity ; c coracoid ; ess indicates the position of
the coraco-sc.ipular suture, obliterated in adult animals by the complete ankylosis
of the two bones ; si suprascapular border.

may be called coracoid border ; the second (gb) joins the
prominent margin of the glenoid fossa, and may, for the
same reason, be called glenoid border ; the third (s) has a
free end, usually more or less prolonged into a curved,
flattened process, called the acromion (a).

The flat or concave surfaces or fossae between these pro-
jecting lamellae are— (i) the prescapular or anterior fossa

248 THE SHOULDER GIRDLE. [CHAP.

(af), between the coracoid border and the spine, called, in
works on human anatomy, "supraspinous fossa;" (2) the
postscapular fossa (pf\ between the glenoid border and the
spine, also called " infraspinous fossa ; " and (3) the sub-
scapular fossa, between the coracoid and glenoid borders
on the side of the scapula opposite to the spine.

The greater part of the scapula is ossified by ectostosis (as
the shaft of a long bone) from a single centre, which is
placed not far from the middle of the bone ; but this ossifi-
cation does not extend into a certain portion near the
superior (or dorsal) extremity. This part (suprascapula
of Gegenbaur) either remains cartilaginous or " is feebly
ossified by one or more endosteal patches, or by the creeping
upwards of such deposit from within the main bone "
(Parker). When the spine runs out into a projecting
acromial process, more or less of its terminal portion is
ossified separately as an epiphysis.

The coracoid always ossifies from one or more separate
centres, and remains for some time suturally connected
with the scapula, though firmly ankylosing with it by the
time the animal has attained maturity. Sometimes (as in
the Sloths) it forms a considerable part of the glenoid fossa ;
sometimes (as in most Carnivora and Ungulata) it is a mere
nodule, which becomes blended with the anterior margin of
the fossa.

In the Ornithodelphia (see Fig. 84), as in Birds and Rep-
tiles, the coracoid is largely developed, and articulates with
the presternum, and there is in addition a plate of bone in
relation with its ventral edge called epicoracoid. A small
plate of cartilage or bone, often found attached to the side
of the presternum in certain Rodents and Insectivores, is
considered by Parker as representing the epicoracoid of
the Ornithodelphia, and by Gegenbaur as the sternal ex-

xiv.] PRIMATES. 249

tremity of the true coracoid, the middle part of which is
undeveloped.

The clavicular arch, when completely developed, extends
from the free acromial extremity of the spine of the scapula
to the anterior extremity of the presternum.

It consists mainly of an elongated rod of bone, ossified
usually in fibrous tissue, but at either extremity are certain
patches of true cartilage, which may become converted into
bone, or may sometimes degenerate into fibre-cartilage.
These are thus described and named by Parker. At the
scapular extremity of the clavicle, there is often a piece of
cartilage considered to be segmented off from the end
of the mesoscapula, and hence called mesoscapular segment
(Fig. 77, mss). At the sternal extremity there may be two
distinct pieces, the one (pc) nearest the clavicle being the
supposed homologue of a displaced fragment of the pre-
coracoid (Gegenbaur and Parker) of the lower vertebrates.
The one (osf) nearest the sternum is called omosternum by
Parker, and episttrnum by Gegenbaur, who considers it
homologous with the so-called episternum (jntcrclaviele,
Parker) of the Ornithodelphia and Lizards.

Special Characters of the Shoulder Girdle in the Different
Groups of the Mammalia.

Order PRIMATES. Man. — In the ordinary erect position
of the human body, the suprascapular border is directed
backwards and inwards, and is commonly called the " base "
or " vertebral border " of the scapula ; the glenoid cavity
looks forwards and outwards; the glenoid border, called
" external " or " axillary," looks downwards and rather
forwards; and the coracoid border is "superior." The

250

THE SHOULDER GIRDLE.

[CHAF.

postscapular fossa is much developed, and the suprascapular
border is long, straight, and forms an acute angle with the
glenoid border. At the junction of the coracoid border of
the scapula with the coracoid bone, there is a more or less
well-marked notch (coraco-scapular notcJi). The spine is
well developed, and the acromion large and curved forwards
near its extremity.

IG. 77. — The hitman sternum and right shoulder girdle at a very early period of
development (from an embryo si inches long) after Parker, i\. The dotted parts
are still cartilaginous ; the inner surface of the sternum and clavicle, and outer
surface of the scapula are represented, ost omosternum, afterwards developed
into the interarticular fibro-cartilaginous disk; pc precoracoid of Parker; cl shaft
of the clavicle ; mss mesoscapular segment of Parker ; a acromion ; c coracoid ;
gc glenoid cavity of scapula ; gb glenoid border ; cb coracoid border ; of anterior,
or ''supraspinous," fossa; ^/"posterior, or '' infraspinous," fossa ; S.T suprascapular
border.

The coracoid forms a well-marked hook-like process ; it
contributes a very small part to the glenoid fossa, and unites
with the scapula about the time of puberty.

The clavicle (Fig. 77, d] is a strongly-developed sigmoid
bone, remarkable for the very early age at which it com-
mences to ossify, in fact before any other bone of the body.
The outer extremity is, in the young state, tipped with

xi v.l INSECTIVORA. 251

cartilage (the mesoscapular segment, Parker, tnss), which
ossifies by extension of bone from the rest of the clavicle.
It is connected with the acromion by a small oval, flat,
synovial articulation. The inner end (pt) is also cartila-
ginous for some time, but ossifies separately by endostosis,
forming an epiphysis. This extremity is attached to the
presternum by synovial articulation, but with a disk-like
fibro- cartilage (ost) interposed, which, according to Parker,
is a degeneration of the " omosternal " element.

In the Gorilla the scapula is very like that of Man. In
the Chimpanzee it is peculiarly elongated, the suprascapular
margin being extremely oblique and long, at the expense
of the greatly reduced coracoid border. The acromion and
coracoid are largely developed. In the lower Monkeys the
form of the scapula is quite different, the coracoid and
glenoid borders being nearly equal, and the suprascapular
border comparatively short and straight.

The clavicle is well developed in all the Primates,
and all its correlates are present ; the omosternum being
generally converted during growth into a fibro-cartilaginous
intra-articular disk.

In the various members of the Order INSECTIVORA there
is a great difference in the construction of the shoulder
girdle.

In the Mole (Talpa) and its immediate allies, Sea lops and
Condylura, the scapula is extremely high and narrow, and
appears to be ossified entirely from one centre. The spine
and acromion are very little developed. The bone com-
monly called clavicle, but which may be a combination of
coracoid and clavicle, is of remarkable form, being nearly
cuboid. It is formed primitively of a mass of cartilage, on
the anterior aspect of which the true (membrane-developed)
clavicle is engrafted. It articulates inferiorly with the pre-

THE SHOULDER GIRDLE.

[CHAP.

sternum, and superiorly with the humerus, and is connected
with the scapula only by a fibrous band. The two articula-
tions of the upper end of the humerus, the one with the
scapula, and the other with the coraco-clavicle, are separated
by a strong ligamentous partition.

In the Cape Golden Mole (Chrysochloris) the condition of
these parts is quite different. The scapula is long and
narrow, but flattened. The spine sends a flat process back-
wards near its middle, and a long slender " metacromial"

FIG. 78. — Shoulder girdle, with upper end of sternum (inner surface) of Shrew (Sorcx),
after Parker, X 7. ps presternum ; srl first sternal rib ; sr* second sternal rib;
ec partially ossified " epicoracoid " of Parker, or rudiment of the sternal extremity
of the coracoid ; ost omosternum ; pc rudiment of precoracoid (Parker) ; cl cla-
vicle ; mss ossified " mesoscapular segment;" a acromion : ma metacromial
process ; c coracoid.

process from its extremity. The clavicle is very long,
slender, and curved. The " mesoscapular segment " forms
a distinct, though minute, bone between the clavicle and
scapula.

In the Shrews (Soricidee) the scapula (see Fig. 78) is
also long and narrow, and the slender acromion ends in
two long diverging processes, of which the anterior (a)
supports the clavicle and the posterior (ma) is called

xiv.] RODENTIA. 253

"metacromion." The mesoscapular segment (mss) is a
distinct bone. The clavicle (cf) is long and slender. It has
a small piece of cartilage (pc] attached to its inner end.
The omosternum (osf) is cartilaginous or partially ossified,
and there is a considerable triangular flattened rudiment
of the inner end of the coracoid (tc) attached to the pre
sternum.

In the other Insectivora the general form of the scapula
is more normal. In Galeopithecus the coracoid is greatly-
developed and bifurcated.

All known members of the order have large clavicles, with
the exception of Fotamogale, a rare aquatic form from
West Africa.

In the CHIROPTERA the scapula is large, of an oval form,
and chiefly formed by the postscapular fossa, the anterior
fossa being extremely small. The former is divided into
two or three subfossse by ridges. The spine is short and
moderately high, with a large and simple acromion. The
coracoid is long and curved, often simple (as in Pteropus)
sometimes forked (as in Pipistrellus).

The clavicle is very long and curved. The " mesoscapular
segment " on the outer end is soon lost, but the precoracoid
ossifies separately. The omosternum is reduced to a
cuneiform fibro-cartilage. A rudiment of the sternal end of
the coracoid is often present as "a flat, reniform flap of
cartilage, feebly ossified by endostosis, wedged in between
the clavicle and the first rib " (Parker).

The RODENTIA offer great diversities in the condition of
the shoulder girdle. The scapula is generally high and
narrow, and the acromion long. Sometimes the acromio-
scapular notch is so deep, that the actual spine only occupies
a short space near the suprascapular border, and it is com-
pleted by a very long and slender acromion (as in the Coypu,

254

THE SHOULDER GIRDLE.

[CHAP.

Myopotamus]. There is often a long metacromion, as in the
Hare ; but in others, as the Beaver, there is no such process.
The coracoid is always a small blunt hook.

In a few forms the clavicle is altogether absent, in some it
is well developed, and various intermediate stages between
these two extremes are met with. In some species, as the
Guinea Pig and Rabbit, although no trace of this bone is
found at birth, it becomes developed at a later period. In
both of these it is very short, and is suspended by long

ps

FIG. 79. — Shoulder girdle, with upper end of sternum (inner surface), of a young
Rabbit (Lc/>ns citniculus), after Parker. 3. ps presrenuim ; srl first sternal rib;
ost om asternal cartilage ; fc precoracoid cartilage ; c/ossified clavicle ; HISS carti-
laginous mesoscapular segment ; c coracoid ; a acromion ; ma metacromion : af
anterior fossa ; pf posterior fossa.

ligaments between the scapula and the sternum. (See Fig.
79.) In many species, as in the Porcupines, in which the
clavicular arch is more complete, the true clavicle is con-
nected with the presternum by a long cartilaginous omo-
sternum. In others, as the Beaver, this is replaced by a
ligamentous band. Rudiments of the sternal end of the
coracoid are often present, sometimes cartilaginous, some-
times ossified.

xiv.] CETACEA. 255

In the CARNIVORA the anterior and posterior fossae of
the scapula are nearly equal in area. (See Fig. 76, p. 247.)
The spine and acromion are fairly developed, the latter often
with a broad metacromial process. The coracoid is much
reduced. According to Parker a portion of the scapula,
near the coracoid border, ossifies from an independent
centre. The clavicle is sometimes absent, and when present
varies much in its development, but is always rudimentary
and suspended in the muscles, never reaching either the
acromion or sternum. In the Felida it is slender and
curved, being longer than in any other members of the order.
In the Canidce it is very short, and rather broad and flat.
In most of the Ursida it is absent.

In the Seals both acromion and coracoid are much re-
duced, but the latter is a distinct bone in young animals,
and forms a considerable part of the glenoid cavity. The
whole scapula is much curved backwards, being almost
sickle-shaped, and the suprascapular epiphysis is very large
and slowly ossified.

In the Eared Seals (Otaria) the scapula has a different
form, the prescapufar fossa being very much larger than the
posterior, and with a strong vertical ridge, parallel to the
spine.

None of the Pinnipedia have clavicles.

Order CETACEA. — In the true Dolphins and nearly all the
Odontoceti the scapula is usually very broad and flat, or fan-
shaped. (See Fig. 80.) The prescapular fossa (af) is ex-
tremely reduced ; the acromion (a) is a long flat process
with a very narrow base of attachment, projecting for-
wards ; the coracoid (c) is rather long, flattened, and parallel
with the acromion.

In the Cachalots (Phystter) the scapula is formed on the
same general plan, but is comparatively high and narrow.

256

THE SHOULDER GIRDLE.

[CHAP.

The postcapular fossa is very concave, and the subscapular
fossa convex. The Gangetic Fresh-water Dolphin (Platanista)
has a flat flabelliform scapula, with the prescapular fossa
entirely absent, and the acromion placed on the anterior
edge, the spine and the coracoid border having coalesced.

Among the Whalebone Whales, Balcenoptera has a broad
fan-shaped scapula, like that of the true Dolphins, with long
parallel acromion and coracoid processes, and a suprascapular

IG. 80. — Right scapula of Dolphin (Delphintis turtle), \. gc glenoid cavity ;
a acruinion ; c coracoid ; pf postscapular fossa ; of prescapular fossa.

border which remains permanently in a cartilaginous con-
dition. In the Right Whales (Bal&nd) the scapula is more
massive and not so broad, and the coracoid is much reduced.
In Megaptera the scapula is triangular, and neither the
coracoid nor the acromion forms a distinct process.

None of the Cetacea possess clavicles.

The scapula of the SIREXIA is formed on quite a different
plan, being rather like that of the Seals in shape, narrow,
and curved backwards. The anterior fossa is nearly as
large as the posterior. The spine is moderately developed.

xiv. UNGULATA. 257

and the slender acromion points downwards. The coracoid
forms a moderate-sized conical process. There are no
clavicles.

In the UNGULATA the scapula is always high and rather
narrow. The prescapular and postscapular fossa; are often

Fl<;. 81.— Right scapula of Red Deer (Crrrus eltf-has), \. st partially ossified
_suprascapular border: pf postscapular fossa; af anterior or prescapular fossa;
a acromion ; c coracoid : gc glcnoid cavity.

subequal. The acromion and coracoid are never much
developed. The clavicle is always absent.

The Pecora (see Fig. 81) have all a very large and very
slowly and imperfectly ossified suprascapular region (ss) ;
when this is removed, as is almost always the case with
macerated bones, the upper border of the scapula is very
straight. The acromion usually forms a distinct process,

258 THE SHOULDER GIRDLE. [CHAP

but is quite absent in the Giraffe, which has the longest and
narrowest scapula of the group.

In the Horse the scapula is long and slender, the supra-
scapular border is rounded, and slowly and imperfectly
ossified. The spine is very slightly developed ; rather above
the middle its edge is thickened and somewhat turned back-
wards ; it gradually subsides at the lower extremity without
forming any acromial process. The coracoid is a prominent
rounded nodule.

In the other Perissodactyles, and in the Pigs and Peccaries,
there is a strongly-marked retroverted triangular process
on the middle of the edge of the spine, and no true
acromion ; but in the Hippopotamus there is a small
acromion and no distinct mid-spinous process. In this
animal the coracoid is rather long and upturned.

In the Tapir the coraco-scapular notch is remarkably
deep.

The Hyrax manifests, its affinity with the Ungulata in the
form of the scapula, which is generally triangular, with a
small spine, most prominent and with a retroverted edge
near the middle, and gradually subsiding at each extremity)
so that there is no trace of an acromial process.

The Elephant has a largely-developed postscapular fossa
and a narrow anterior fossa. The glenoid border is short,
and forms a very prominent angle posteriorly with the
unusually long suprascapular border. The spine is promi-
nent, and has a very strongly-marked process projecting
backwards from near the middle and a moderate-sized
acromion. The coracoid is small and rounded.

The EDENTATA present some very interesting conditions
of the shoulder girdle.

In the Cape Anteater (Orycteropus) the scapula is of
the most normal form, with well-developed acromion and

xiv.] EDENTATA. 259

coracoid. The middle of the border of the spine is thick-
ened and retroverted, and there is a well-marked meta-
cromion. The clavicle is strong, curved, and dilated at its
sternal end.

In the Pangolins (Alan is) the scapula is broad, and rounded
above, the anterior margin gently passing into the superior.
The prescapular fossa is broader than the postscapular. The-
suprascapular region remains cartilaginous. The acromion
is very small. The coracoid is extremely rudimentary, but
with a separate ossific nucleus. There are no clavicles.

In the Anteaters (Afyrmecophagidai) the scapula is also
broad and rounded, so that there is no distinct angle between
the anterior and superior margin. The anterior margin is
produced, to meet the large adze-shaped coracoid over the
coraco-scapular notch, converting it into a foramen. The
spine has a triangular process in the middle, and a long
slender acromion, without distinct metacromion. The post-
scapular fossa is nearly equally divided by a second spine.

Rudimentary flat clavicles imbedded in muscles are
present in both Tamandua tetradactyla and Myrmecophaga
jitbata.

The small climbing Cydoturus didactylus has moderate
gently curved clavicles.

In the Armadillos (Dasypodidai) the scapula is rather
varied in form. The acromion is always very long and
curved ; in many cases it has a distinct articular facet on its
inner surface for the upper end of the humerus. (See Fig.
82, //.) There is a second spine on the postscapular fossa,
and always a well-developed clavicle.

In the Sloths (Bradypodida, Fig. 83) the prescapular
region (of) is larger than the postscapular (pf\ The spine
arises from little more than the middle third of the bone,
vertically. In the young of both genera of this family the

26o

THE SHOULDER GIRDLE.

[CHAl'.

acromion is a long strip of cartilage connecting the spine
with the end of the coracoid, while the coracoid border of
the scapula and the coracoid bone join each other in front
converting the coraco-scapular notch into a small oval fora-
men (csf\ The acromion and coracoid remain united in the
Two- toed Sloth (Cholxpus) and the extinct Megatherium;
but in Bradypus the acromion gradually becomes reduced in

FIG. 82. — Right scapula of Great Armadillo (friodon gigas), \. // postscaptilar
fossa ; rt/prescapular fossa : gc glenoid cavity ; csn coraco-scapular notch ; c cora-
coid ; a acromion ; h articular surface for humerus.

size, losing its connection with the coracoid, and finally
remains a mere styliform, or slightly flattened process.

The coracoid in both forms is unusually large, ossifies
ectosteally according to Parker, and has an epiphysis on its
free hook-like extremity.

The clavicle (cl) of Cholcepus is well developed, attached
external to the loop of bone on the scapula, formed by the

xiv.] EDENTATA. 261

united extremities of the acromion (a) and coracoid (^), and
internally by the intervention of a long fibre-cartilaginous
" omosternum " (degenerating into a mere ligament in the
adult) to the presternum. In Bradypus the clavicle is very
small, and separated by a long interval from the sternum.
It originally articulates at its scapular end, as in Cholapus ;
but in consequence of the atrophy of the acromion, it is

FIG. 83.— Right scapula and clavicle of Two-toed Sloth (Cholafius hoffntanm), i\.
af prescapular fossa ; />/ postcapular fossa ; %c glenoid cavity ; a acromion
c coracoid ; «/ coraco-scapular foramen ; cl clavicle.

left attached to the end of the coracoid, in which unusual
situation it remains through adult life.

In the MARSUPIALIA the scapula is tolerably uniform in
shape. The acromion is long, and the coracoid small, of a
somewhat hooked form, and thick at the base. It ossifies
by a separate endosteal nucleus.

The clavicle is present in all known Marsupials except

262 THE SHOULDER GIRDLE. [CHAP.

the Bandicoots (Peramelida). It has always a "mesosca-
pular segment" as its outer end, and a " precoracoid seg-
ment " at its sternal end ; these are, however, not ossified.
Most generally it is attached to the acromion by a rather
strong ligament, but in the Wombat by a synovial articu-
lation. It is usually connected to the presternum by omo-
sternal cartilages of varying length, best developed in the
Didelphida.

The shoulder girdle of the MOXOTREMATA (see Figs. 84 and
85) differs widely, in many points, from that of any other
Mammal, and far more resembles that of the Lizards.

The scapula is rather long and narrow, and (especially in
the Ornithorhynchus) curved backwards and pointed, sickle-
like, at its upper end. Instead of three it presents but two
distinct borders and two surfaces ; but the more convex
border (s), which is turned forwards and outwards in its
natural position, has a small projection (a) near its lower
end, which affords attachment to the clavicle, and is evidently
the acromion ; and the whole border may be considered to
represent the spine. Following the indications afforded by
the attachment of the muscles, it appears probable that the
whole inner surface represents the prescapular fossa of the
ordinary Mammalian scapula, and that the anterior portion
of the outer surface (pf) is the postcapular fossa, and the
posterior portion of the same surface (ssf) the subscapular
fossa, these two being divided below by a slight ridge (gb),
which runs to the edge of the glenoid cavity, and from which
the long head of the triceps muscle takes origin. This
ridge then answers to the posterior or glenoid border of the
ordinary Mammal, and the hinder border of the Monotreme's
scapula (cb) would correspond to the anterior or coracoid
border. If this is really the case, the scapula of the Mono-
treme and that of the Cetacean offer the widest contrast,

xiv.] MONOTREMATA. 263

the supposed primitive trihedral rod being flattened in
opposite directions. In the Cetacean scapula there are two
nearly parallel surfaces, the postscapular and the subsca-
pular fossse ; while the third, the prescapular fossa, is reduced
to the smallest possible width — quite obsolete, in fact — in
Platanista. In the Monotreme the last-named fossa is so
expanded that the other two, instead of being parallel to

Fio. 84. — Side view of right shoulder girdle of a young Echidna (Echidna hystrix), ,
ss suprascapular epipnysis ; uf subscapular fossa ; //" postscapular fossa ; cb
coracoid border ; gf> Ctenoid border ; s spine ; a acromion ; ess coraco-scapular
suture ; gc glcnoid cavity ; c coracoid ; ec epicoracoid ; cl clavicle ; ic interclavicle ;
pi prcstcrnum.

each other on opposite sides of the bone, are brought almost
into one plane, which is parallel and opposite to the sub-
scapular fossa.

The coracoid (c) is a stout subcylindrical bone, expanded
at its extremities, taking at its upper end a considerable
share in the formation of the glenoid cavity, and becoming
firmly ankylosed with the scapula. At its lower end it

25.| THE SHOULDER GIRDLE. [CHAP.

articulates to the side of the presternum, just in front of the
first rib.

Placed in front of the inner end of the coracoid is a
broad, flat, shield-like plate of bone (epicoracoid, ec Fig. 84,
Prc, Fig. 85), the rounded inner border of which passes
beyond the median line, overlapping the corresponding bone
of the opposite side. In the Echidna the left lies superfici-
ally to the right, while in the Ornithorhynchus this disposition
is reversed.

Upon the front end of the presternum, lying below its
anterior continuation (proosteon, see p. 104) and also below

FIG. 85. — Ventral view of shoulder-girdle and anterior portion of sternum and
sternal ribs of Ornithorhynchus (O. ^anatinns) ; £. sc scapula; cl calvicle ;
c coracoid ; Prc epicjracoid ; Kp interclavicle or episternum.

the epicoracoids, is a large azygous T-shaped bone (ic Figs.
84 and 44 ; Ep Fig. 85), which has no homologue in any
other Mammal, called interclavicle or episternum. Its lower
end is broad, and rests on the expanded straight upper
margin of the presternum ; it contracts somewhat above
before dividing into a pair of nearly horizontal, slightly-curved
arms, which extend outwards towards, though not quite
reaching, the acromion. This bone differs from the pre-
sternum, and the small proosteal plate behind its lower

xiv.] MONOTREMATA. 265

extremity, as well as the coracoids and epicoracoids, in being
developed in membrane.

The clavicles (d) are simple, elongated, slightly curved,
thin, splint-like bones, resting upon the anterior surface of
the arms of the interclavicle, pointed and not quite meeting
internally, and dilated and articulating directly with the
acromion at their outer end.

CHAPTER XV.

THE ARM AND FORE-ARM.

IN the upper segment of the limb proper there is always
one bone, the If it merits ; in the second segment, two bones
placed side by side, the Radius and Ulna.

The Humerus (except in some of its extreme modifica-
tions) is more or less elongated and cylindrical. It is
described as having a shaft, and two extremities. The upper
or proximal extremity has a smooth, convex, generally more
or less rounded head (Fig. 86, //), the axis of which is
directed upwards and backwards.1 This, in the living
animal, is covered with a thin layer of cartilage, and
articulates by a synovial joint with the glenoid cavity of the
shoulder girdle. The head is marked off from the shaft
very indistinctly by a constriction called the neck, imme-
diately below which, upon the anterior surface of the bone,
are two rough prominences (/ and /') for the attachment of
muscles, called tnberosities, separated from each other by a
groove (bg) called the bicipital groove, as the tendon of the
biceps muscle runs in it after arising from the margin of the
glenoid fossa. The tuberosities are generally distinguished

1 The terms of relative position here used are those which the bone
assumes in the ordinary attitude of a quadruped while standing or
walking.

CH. xv.] GENERAL CHARACTERS. 267

as great (/) and small (/') from their relative size in Man and
most other Mammals ; the former is also called external, and
the latter internal, from their relative situation in the most
usual position of the bone.

The lower or distal extremity of the humerus is some-
what flattened, and usually has a broad, semi-cylindrical
articular surface, which is received into a corresponding

FIG. 86.— Anterior surface of right humerus of Wombat {Phascolomys romtatus), J
k head ; l>g bicipitnl groove ; / great or external tuberosity ; f small or internal
tuberosity ; fir deltoid ridge ; sr supinator ridge ; cf supra-condylar foramen ;
ec external condyle ; ic internal condyle ; ar articular surface for radius ; au arti-
cular surface for ulna.

concavity on the upper end of the bones of the fore-arm.
This is called the trochlea (ar and au). On each side, and
rather above this surface, is a prominence called the condyle,
one of which is external, or radial (ec), the other internal, or
ulnar (ic). The latter is usually the most prominent.1 In

1 "In anthropotomy, the term 'condyle' rightly applied to the
prominent articular convexities of the occipital, mandibular and femoral

268 THE ARM AND FORE-ARM. [CHAP.

the middle of the lower end, between the condyles, and
above the thickened articular border, the bone is very thin,
having a hollow both in front and behind. The latter,
which is the deepest, is called the anconeal fossa, as it
receives a projecting part of the anconeal process, or ole-
cranon, of the ulna, when the fore -arm is fully extended.
It often happens that these two fossas are so deep that they
meet, and there is in consequence a vacuity in the bone
called the siipratrochlear or intercondylar foramen. There is
usually a prominent ridge running upwards for some distance
on the shaft from the external condyle, called the ectocondylar
or supinator ridge (sr), which affords a wide surface of origin
for the supinator muscles of the fore-arm. When much
developed this ridge terminates above at the groove for the
passage of the musculo-spiral nerve. When the edge of the
bone above the inner condyle is much developed, it is some-
times grooved, but more often obliquely perforated from
above, downwards and forwards, by a supracondylar foramen
(cf\ through which the median nerve and brachial artery
may pass. Lastly, somewhere towards the anterior sur-
face of the middle of the shaft, on the outer side, there is
usually a roughened, elevated, longitudinal ridge (dr), some-
times developed into a tuberosity, for the insertion of the
deltoid muscle, and hence called the deltoid ridge. The
lower end of this ridge is separated from the upper end of
the supinator ridge by a wide and shallow groove, winding
in a spiral manner downwards and forwards round the outer

bones, is transferred from the distal articular prominence of the humerus
to the processes for attachment of muscles above the joint surfaces.
I have found it convenient in comparative osteology to indicate the
homologies of the ' external condyle ' and ' internal condyle ' of the
human humerus by the terms ' ectepicondyle ' and ' entepicondyle '
(Owen)." By French anatomists they are called epicondyle and epi-
trochlea respectively.

xv.] GENERAL CHARACTERS, 269

side of the shaft of the bone, and indicating the course of
the musculo-spiral nerve.

The whole of the shaft of the humerus is developed
ectosteally from a single centre of ossification, but at each
extremity there is a large epiphysis : the upper one includes
the head and both tuberosities, and is usually formed by the
coalescence of two distinct endosteal nuclei ; the lower one
includes the whole inferior articular surface with the condyles,
and is formed of three or four originally distinct centres of
ossification. The lower epiphysis unites to the shaft before
the upper one.

The skeleton of the second segment of the upper limb,
the fore-arm or antibrachium, consists of two bones called
radius and ulna, placed side by side, articulating with the
humerus at their proximal, and with the carpus at their
distal, extremity.

In their primitive or unmodified condition, these bones*
may be considered as placed one on each border of the
iimb, the radius being preaxial, and the ulna postaxial.1
The radius articulates above with the preaxial (external)
side of the humerus, the ulna with the postaxial (internal)
side of the humerus.

This position is best illustrated in the fore-limb of the
Cetacea (see Fig. 104), where the two bones are fixed side by
side and parallel to each other, the preaxial border being
external, and the postaxial border internal, in their whole
extent.

In the greater number of Mammals, the bones assume a

1 So termed (by Prof. Huxley) in relation to the assumed central axis
of the limb, when it is extended out from the body in a certain stage of
its embryonic position, the extensor surface of the arm and back of the
hand being upwards or dorsal, and the flexor surface of the arm and palm
of the hand being downwards or ventral.

270 THE ARM AND FORE- A KM. [CHAP.

very modified and adaptive position (as will be explained
more fully in the chapter on the comparison of the fore and
hind limbs), usually crossing each other in the fore-arm, the
radius in front of the ulna, so that the preaxial bone
(radius), though external (in the ordinary position of the
limb) at the upper end, is internal at the lower end ; and
the hand being mainly fixed to the radius, also has its pre-
axial border internal. In the large majority of Mammals
the bones are fixed in this position ; but in some few, as
in Man, a free movement of crossing and uncrossing, or
pronation and supinaiion, as it is termed, is allowed between
them, so that they can be placed in their primitive parallel
condition, when the hand (which moves with the radius) is
said to be supine, or they may be crossed, when the hand is
said to be prone.

In most Mammals which walk on four limbs, and in which
the hand is permanently prone, the ulna is much reduced in
size, and the radius increased, especially at the upper end ;
and the articular surface of the latter, instead of being con-
fined to the external side of the trochlea of the humerus,
extends all across its anterior surface, and the two bones,
instead of being external and internal, are anterior and
posterior (see Figs. 87, 88, and 89).

The ulna is always characterised by a conspicuous, more
or less compressed prolongation, extending upwards beyond
the excavated humeral articular surface (sigmoid notch), and
serving as the point of attachment to the extensor muscles
of the fore-arm, called the olecranon or anconeal process.

Each of the bones of the fore -arm has commonly a
principal centre of ossification for the shaft, and an epiphysis
at either end.

PRIMATES.

271

Special Characters of the Bones of the Arm and
Fore-ami in the different Groups.

Order PRIMATES. — In Man the humerus is long, slender,
and straight, with a large globular head. Neither the tube-
rosities, nor the deltoid and supinator ridges, are much
developed. The internal condyle is prominent, but there is
no supracondylar foramen as a normal condition. The
anconeal fossa is wide and deep, and sometimes, though
not usually, jxjrforated. The lower articular surface is divided
by a groove into a pulley-like internal portion (trochlea} for
the ulna, and a smaller rounded portion (capitelluni), confined
to the front side of the bone, for the radius.

The whole bone is somewhat twisted on its longitudina
axis. Supposing it is so placed that a line drawn horizontally
though the axis of the head passes directly backwards,
another line drawn through the condyles would not cross
this at a right angle, as in most of the inferior Mammals, but
its outer end would be directed forwards. This appears to be
caused by a process of resorbtion and new deposition of bony
tissue during the growth of the embryo, producing an effect
resembling torsion of the axis to an extent of about 35°. a

The radius has the head or proximal end expanded, disk-
shaped, and cupped at its extremity, which is applied to the
capitelluni of the humerus (see Fig. 87). Below this
expanded head the bone is comparatively slender, but
increases in size as it approaches the lower end, which is
wide from side to side ; the surface next the ulna being
hollowed to receive the lower end of that bone, while the

1 See Gcgenbaur, " Jenaischc Zeitschrift," Bd. IV. p. 50, nlso his
" I,ehrl)uch der Anatomic des Mcnschen." Leipzig, 1883. For an
opposite view, Albrecht, " Bcitragzur Torsionstheorie, etc." Kiel, 1875

273 THE ARM AND FORE- ARM. [CHAP.

opposite side is produced into the radial styloid process.
The inferior surface is hollowed for articulation with the
carpus. The whole bone is slightly curved. Not far below
the head is a rough prominence, into which the tendon of
the biceps flexor muscle is inserted.

The ulna has a large sigmoid excavation above for articu-
lation with the trochlea of the humerus ; the pointed elevated
anterior edge of this is called the coronoid process. The
olecranon is scarcely produced upwards beyond the hinder
edge of the articular surface. Below this, on the radial side,
is a smaller excavation, in which the edge of the disk-like
head of the radius plays, being held in its place in the living
state by a strong annular ligament, which encircles it. The
ulna is straighter than the radius, and gradually diminishes
in size to the lower end, where it terminates in a rounded
surface, which articulates with the hollow in the lower end
of the radius ; and also, though not very directly with the
proximal surface of the carpus. The ulnar side is produced
into a small conical process, the ulnar styloid process.

The movement of these bones upon the humerus at the
elbow-joint is simply that of a hinge, formed mainly by the
articular surface of the ulna. In pronation and supination,
which is more free and complete than in any other Mammal,
the ulna is stationary, and the radius moves ; the upper end
only on its own axis, being fixed to the side of the ulna by
the annular ligament, but the lower end rotates round the
lower end of the ulna, carrying the hand with it.

The higher Apes have the axis of the humerus almost as
much twisted on itself as in Man ; and they also, almost
alone among Mammals, resemble Man in not having the
olecranon process of the ulna prolonged upwards beyond
the sigmoid notch. Even in the Baboons these special an-
thropoid characters are wanting. The humerus has no supra-

XV.]

CARNIVORA.

273

condylar perforation in any of the Old World Simiina, nor in
Ateles, Mycetes or Hapale among the American Monkeys ;
but in the remaining genera of Cebida, and in most of the
Lemurs, such a perforation is found. In the Aye-Aye
(Chiromys) the supinator ridge is remarkably developed.
The radius and ulna are distinct in all ; in the higher forms
(especially the Gorilla) greatly curved, leaving a large space

FIG. 87. FIG. 88. FIG. 89.

Anterior aspect of the bones forming the right elbow-joint of Man (Fig. 87) ; of the
Dog (Fig. 88) ; of the Red Deer (Fig. 89) ; all J. h humerus ; r radius ; u ulna.

between them in the middle of the fore-arm. The power of
supination and pronation, which in the higher forms almost
equals that enjoyed by Man, is much reduced in the inferior
types of the order, although never entirely lost.

In the CARNIVORA the head of the humerus has no longer
that hemispherical form, so well marked in the higher
Primates. The tuberosities are strong and rough, and
project upwards beyond the level of the head. The shaft

274 THE ARM AND FORE-ARM. [CHAP.

is much curved forwards. The deltoid ridge is strong, and
extends far down on the bone, especially in the Bears. The
inner condyle is prominent. The anconeal fossa is deep. A
supracondylar foramen exists in the Felidce, and in most of
the Viverridce, Mustelidtz, and Procyonidce, but not in the
Canidce, Hycenida, or Ursidiz.

The radius differs from that of Man, inasmuch as its
upper end is broad, flattened, and extends further across the
front of the humeral articular surface, forming part of the
hinge (see Fig. 88) ; and although it is never ankylosed with
the ulna, scarcely any appreciable amount of movement is
allowed between them. The ulna has a large compressed
olecranon, and a shaft gradually tapering to the lower
extremity.

In the Pinnipedia the bones of the anterior limb are very
short and stout. The humerus has a remarkably prominent
deltoid ridge, and usually no supracondylar foramen, though
this is present in the Common Seal (P/wca ritulina}. The
upper end of the ulna, and conversely the lower end of the
radius, are much expanded.

In most of the INSECTIVORA the bones of the arm gene-
rally resemble those of the Carnivora. In the Hedgehog
(Erinaceus) there is no supracondylar foramen in the
humerus, but a large supratrochlear perforation. In Centetes
Rhynehocyon, and nearly all the other genera, there is a
supracondylar foramen.

The radius and ulna are generally completely developed
and distinct ; but in Galeopithecus, Macroscelides and Petro-
dromus, they are fused together distally.

The Mole (Talpa) and its allies have a humerus of ex-
traordinary form (see Fig. 34, p. 95), being very short, and
extremely broad and flattened at both extremities, though
contracted in the middle. In addition to the narrow oval

XY.] JNSECT1VORA. 275

head for articulation with the glenoid cavity ot the scapula,
there is a larger saddle-shaped surface, which articulates by
a separate synovial joint with the outer end of the coraco-
clavicle. The deltoid ridge is very prominent, joining the
inner tuberosity above. From each condyle a slender bony
process extends upwards. There is a supracondylar fora-
men. The ulna has a greatly developed olecranon, with a
narrow keel behind, and expanded laterally at the extremity.

In the Cape Golden Mole (Chrysochloris) the humerus
is much more slender generally than in the true Moles, but
the inner condyle is extremely elongated. The olecranon
is long, narrow, and incurved The fore-arm has a third
bone, extending from the palmer surface of the carpus
almost to the elbow, where it has a free termination.
This appears to be an ossification in one of the flexor
tendons.

In the CHIROPTERA both arm and fore -arm are long and
slender. The humerus has a slight sigmoid curve, its ulnar
tuberosity is large, and there is no supracondylar perfora-
tion. The ulna is extremely reduced, only the proximal
third being present, and that ankylosed with the radius, which
forms almost the whole of the lower articular surface of the
elbow-joint. There is a detached sesamoid ossicle near the
olecranon, in the tendon of the triceps muscle.

In the RODENTIA the humerus varies much in its charac-
ters. It is long, slender, and straight, with a very slight
deltoid ridge, a narrow and laterally compressed inferior
end, and without prominent condyles in the Hares and
Agutis. But in the Beaver the deltoid and supinator ridges,
and the inner condyle, are strongly developed. All inter-
mediate conditions occur in different genera. As a general
rule there is a large supratrochlear perforation, but no
supracondylar foramen. In the Coypu (Myopotamus) the

T 2

276 THE ARM AND FORE- ARM. [CHAP.

deltoid ridge is an extremely salient, compressed, and
everted tuberosity.

In the fore-arm the two bones are nearly always dis-
tinct, though closely applied to each other. The breadth
of the upper end of the radius, and the amount of
rotation permitted upon the ulna, vary much in different
genera.

In the great order UNGULATA the hnmerus is stout and
rather short. The outer tuberosity is very large, and gene-
rally sends a strong curved process inwards, overhanging the
bicipital groove (not, however, in the Horse and Camel).
The deltoid ridge is usually not strongly marked, and placed
rather high on the bone ; but in the Rhinoceros it is a very
salient ridge. The lower end is always particularly straight
and flat on the inner side (see Fig. 89, p. 273), the condyle
forming no prominence, and there is never a supracondylar
oramen. The outer condyle and the ridge above it are
rather more developed.

The radius is large at both ends, and superiorly extends
across the whole of the humeral trochlear surface (see Fig.
89). The ulna is a complete and distinct bone in the Pig,
Hippopotamus, Tapir, and Rhinoceros. In the Ruminants
it is more or less rudimentary and fixed behind the radius.
In the Camel the two bones become completely coalesced.
In the Horse the olecranon and proximal part of the shaft
alone remain, firmly ankylosed to the radius.

In the PROBOSCIDEA the humerus is remarkable for the
great development of the supinator ridge. The ulna and
radius are quite distinct, and permanently crossed. The
upper end of the latter is small, while the ulna not only
contributes the principal part of the articular surface for the
humerus, but has its distal end actually larger than that of
the radius, a Condition unique among Mammals.

xv.] CETACEA. 277

In Hyrax the humerus is straight, with a very prominent
outer tuberosity, moderate deltoid ridge, rather compressed
inferior extremity, large supratrochlear, but no supracon-
dylar, perforation. The ulna and radius are complete and
subequal, often ankylosing together in old animals.

In the CETACEA, the bones of the arm and fore-arm are
usually very short, broad, and simple in their characters
(see Fig. 103). The humerus has a large globular head,
which moves freely in the glenoid cavity of the scapula,
the tuberosities are fused into one, the bicipital groove
being absent ; the lower end is broad and flattened, and
its inferior surface is divided into two nearly equal flat
surfaces placed side by side (one external, the other internal),
and meeting at a very obtuse angle. The equally flat
upper surfaces of the radius and ulna are applied to these,
and so united that scarcely any motion is permitted between
them, and often in old animals ankylosis takes place at
the joint.

The ulna and radius are parallel to each other without
any indication of crossing : the former has a tolerably well-
developed olecranon process projecting directly outwards
from the shaft of the bone ; the radius is extremely simple
in form, wider distally than proximally.

In the Rorquals (Balanoptera and Megaptera) these bones
are considerably elongated.

In the SIRENIA the bones of the fore-limb are formed on
a different type, as there is a distinct, though small and
simple, trochlear articulation at the elbow-joint. In the
Dugong, the humerus is small in the middle of the shaft,
and expanded at each end. The tuberosities are very pro-
minent, especially the outer one, and the bicipital groove is
distinct The internal condyle is prominent, the anconeal
fossa small, and there is no supracondylar perforation. In

278 THE ARM AND FORE-ARM. [CHAP.

the humerus of the Manatee the bicipital groove is obsolete,
the two tuberosities coalescing, as in the Cetacea. In other
respects it resembles that of the Dugong.

The two bones of the fore-arm are, in both genera, about
equally developed, and generally ankylose together at both
extremities.

Order EDENTATA. — In the Sloths the humerus is long
and straight, slender and cylindrical in the greater part, but
flattened and laterally expanded at the lower end. The
head is hemispherical, the tuberosities moderately developed,
and subequal in size, the deltoid ridge very indistinct. In
the Two-toed Sloths (Chol&pus) the humerus is shorter and
broader than in Brady pus, and has a large supracondylar
perforation, which is wanting in the latter genus.

The radius and ulna somewhat recall those of the
Primates in their form, and they are capable of a con-
siderable amount of pronation and supination. The
olecranon process scarcely projects beyond the sigmoicl
articular surface.

The humerus in all the remaining Edentates is stout and
broad, and remarkable for the great development of the
points of muscular attachment, as the tuberosities, deltoid,
and supinator ridges, and internal condyle. These all
reach their maximum of development in the Armadillos,
animals which make great use of their fore-limbs in
scratching and burrowing. The supracondylar foramen is
present in all.

The radius and ulna are also well developed and
distinct in all, but with no great amount of motion
permitted between them. The olecranon is always long
and strong.

Order MARSUPIALIA. — In the burrowing Wombat (Phasco-
lomys) the humerus is stout, very broad at the distal end,

xv.] MARSUPIALIA. 279

and with strongly developed deltoid and supinator ridges
(see Fig. 84, p. 242.) These characters prevail generally
throughout the order, though in a less marked degree. The
supracondylar foramen is almost always present, some of
the Dasyures being exceptions.

The radius and ulna are always distinct and well-developed
bones. The upper end of the radius is small and rounded,
and more or less rotation is permitted between the bones,
even in the carnivorous forms.

In the animals constituting the order MONOTREMATA,
the humerus is something like that of the Mole, short and
extremely broad at both extremities, with greatly produced
inner and outer condyles, though contracted at the middle
of the shaft.

The radius and ulna are stout, and rather flattened at the
lower end, where they are of about equal size, and closely
applied together. The upper end of the olecranon is
widely expanded laterally.

CHAPTER XVI.

THE MANUS.

THE terminal segment of the anterior limb is the hand
or manus^ Its skeleton consists of three divisions : (i) The
carpus, a group of small, more or less rounded or angular
bones, with flattened surfaces applied to one another, and,
though articulating by synovial joints, having scarcely any
motion between them ; (2) the metacarpus, a series of
elongated bones placed side by side, with their proximal
ends articulating by almost immovable joints with the
carpus ; (3) the phalanges, or bones of the digits, usually
three in number to each, articulating with one another by
freely movable hinge-joints, the first being connected in
like manner to the distal end of the corresponding meta-
carpal bone.

To understand thoroughly the arrangement of the bones
of the carpus in Mammals, it is necessary to study their

1 "On account of the ambiguity arising from the as yet unsettled con-
notation of the terms ' hand ' and ' foot,' I think it better, in a scientific
treatise, to disuse them altogether, and ... to adopt for the anterior
extremity (the carpus and all beyond it) the term manus, and for the
homotypal posterior segment the term pes. The all but necessity for
distinct homological terms for such parts is obvious." — Mivart, " On the
Appendicular Skeleton of the Primates," Phil. Trans. 1867.

CH. XVI.]

GENERAL CHARACTERS.

281

condition in some of the lower vertebrates.1 Fig. 90 repre-
sents the manus in one of its most complete, and at the
same time most generalised, forms, as seen in one of the
Water Tortoises (Chelydra serpentina).

The carpus consists of two principal rows of bones, an
upper or proximal row, containing three bones, to which
Gegenbaur has applied the terms radiah (r), intermedium (/'),

FIG. 90. — Dorsal surface of the right manus of a Water Tortoise (Chelydra ser-
ftntitta), after Gegenbaur. u ulna ; R radius ; » ulnare ; » intermedium ; r radiale ;

c centrale ; 1—5 the five bones of the distal row of the carpus ; m1 — /
metacarpals.

the five

and ttlnare (u), the first being on the radial or preaxial side
of the limb. The lower, or distal row, contains five bones,
called carpale i, 2, 3, 4, and 5 respectively, commencing on
the radial side. Between these two rows, in the middle of
the carpus, is a single bone, the centrale (c).

In this very symmetrical carpus, it will be observed that

1 See Gegenbaur, " Untersuchungen zur vergleichenden Anatomic,"
Ites Heft, Carpus und Tarsus. 1864.

282 THE MANUS. [CHAP.

the radiale supports on its distal side two bones, carpale i
and 2 ; the intermedium is in a line with the ccntrale and
carpale 3, which together form a median axis of the hand,
while the ulnare has also two bones articulated with its
distal end, viz. carpale 4 and 5. Each of the carpals of the
distal row supports a metacarpal.

In the carpus of the Mammalia, there are usually two
additional bones developed in the tendons of the flexor
muscles, one on each side of the carpus, which may be
called the radial and ulnar sesamoid bones ; the latter is
most constant and generally largest, and is commonly known
as the pisiform bone. The fourth and fifth carpals of the
distal rows are always united into a single bone, and the
centrale is often absent. As a general rule all the other
bones are present and distinct, though it not unfrequently
happens that one or more may have coalesced to form a
single bone, or may be altogether suppressed.

The table bilow shows the principal names in use for the
various carpal bones. Those in the second column, being
most generally employed by English anatomists, will be
adopted in the following pages : —

Jtaiiia'.e --- Scaphoid — Naviculare.

Intermedium Lunar Scmiliinare, Lunatum.

Ulnare - Cuneiform - Triquclrum, Pyramidal/'.

Ct nt rale - Central Intermedium (Cuvier).

Carpale \ - Trapezium - Multangnlum inajns.

Carpale 2 = Trapezoi.l -- Mnllattguhiin niinu*.

Carpale 3 Magnum - Capitatum.

P Unciform Ifamatunt, Uncinatnin.

Carpale 5 )

The metacarpal bones, with the digits which they sup-
port, never exceed five in number, and are distinguished by
numerals, counted from the radial towards the ulnar side.
The digits are also sometimes named (I) fiollex, (II) index.

xvi.] GENERAL CHARACTERS. 283

(III) medius, (IV) annularis, and (V) minimus. One or more
may be in a very rudimentary condition, or altogether
suppressed. If one is absent, it is most commonly the
first, next follows the fifth ; the third is never lost, although
either the second or fourth, or both, may be absent.

Excepting the Cetacea, no Mammals have more than three
phalanges to each digit, but they may occasionally have
fewer by suppression or ankylosis.

The first or radial digit (also called pollex) is an exception
to the usual rule, one of its parts being constantly absent,
for while each of the other digits has commonly a meta-
carpal and three phalanges, it has only three bones altogether.
Whether the missing one is the metacarpal or one of the
phalanges, is a subject which has occasioned much dis-
cussion, but has not yet been satisfactorily decided. In
accordance with the most usual custom, the proximal bone
of this digit will here be treated of as a metacarpal.1

The terminal phalanges of the digits are often specially
modified to support the nail, claw or hoof, and are called
" ungual phalanges."

Very frequently a pair of small sesamoid bones are
developed in connection with the tendons passing over the
palmar surface of the articular heads of the metacarpals and
phalanges, and occasionally (as in the Armadillos) a larger
bone of similar nature is met with in the middle of the
same surface of the carpus and metacarpus. More rarely
similar bones occur on the dorsal surface of the phalangeal
articulations.2

Each of the carpal bones ossifies from a single nucleus.

1 See Allen Thomson " On the Ossification of the First Metacarpal
Bone." ("Journ. Anat. Physiology," vol. iii. p. 131.)

2 These are almost always lost in prepared skeletons, but they occur
constantly in the common dog.

THE MANUS.

[CHAP.

The metacarpals and phalanges have each a main nucleus
for the greater part of the bone, and usually an epiphysis at
one end only, this being the distal end of the metacarpals
(except the first), and the proximal end of the first meta-
carpal and of all the phalanges. In many of the Cetacea
epiphyses are found at both ends of the bones, and the
same takes place regularly in the Elephant Seal (Macro-
rhinus leoninus), and occasionally in some other Mammals.1

f-i

FIG. 91. — Bones of the right human carpus, J. s scaphoid ; / lunar ; c cuneiform ;
tin trapezium ; td trapezoid ; in magnum ; it unciform ; / pisiform ; i — v the
metacarpals.

In Man the carpus (see Fig. 91) is short and broad. Its
upper border, by which it articulates with the radius, forms
a regular curve, with the convexity upwards. It has the
three bones of the proximal row — the scaphoid (s), lunar
(/), and cuneiform (c) — distinct ; also the usual four bones
of the distal row, but no central.2 There is a well-developed

1 The first phalanx of the Horse's toe has a distal epiphysis, which
unites to the shaft at a much earlier period than that at the proximal
end. See Struthers "Brit. Assoc. Report, 1885."

2 The os cenlrale carpi has been found in the cartilaginous stage in
the embryo, but disappears early, although in rare cases it persists in
the adult as a separate bone. See E. Rosenberg, " Morphol. Jahrb. ''
I. p. 172. H. Leboucq, " Acad. Roy. Belg." 3rd ser. torn. iv. 1882.
W. Gruber, " Beobachtungen aus der menschlichen unct vergleichenden
Anatomic," IV. Heft. Berlin, 1883.

xvi.] PRIMATES. 285

rounded ulnar sesamoid (the pisiform bone, /) which articu-
lates by a smooth facet with the cuneiform, but no radial
sesamoid. The trapezium (////) has a saddle-like articular
surface for the movable first metacarpal. The magnum
(m\ as its name implies, is the largest bone — rather an
exceptional condition among Mammals ; it has a large
rounded part or head projecting upwards and fitting into a
concavity in the distal surface of the bones of the proximal
row. The unciform (u) has a strong hook-like process
from its palmar surface curved towards the radial side.

The first metacarpal is shorter, though somewhat broader
than any of the others. It is articulated in a different plane
from them, its palmar surface facing towards the ulnar side
of the hand, and it is capable of a considerable range or
movement. The other four metacarpals are nearly equally
developed, diminishing slightly from the radial to the ulnar
side ; their shafts are slender and rather compressed,
especially towards the palmar aspect ; but they enlarge at
each extremity, particularly at the rounded distal end or
head. They are so articulated with the carpus as to allow
of very little motion. The phalanges are of the normal
number to each digit, all broad, convex on their dorsal, and
flattened or slightly hollowed on their palmar, side. The
proximal is the largest, and the ungual the smallest. The
latter is flattened and slightly expanded or spatulate at its
terminal portion. Those of the first, digit or thumb are
stouter than any of the others, those of the fifth digit (little
finger) are the most slender. The third digit is the longest,
the second and fourth somewhat shorter and nearly equal ,
the fifth considerably shorter, and the first still more so.
Sesamoid bones are only developed below the metacarpo
phalangeal joint of the pollex.

In the other PRIMATES, the manus is generally longer an

THE MANUS.

[CHAP.

narrower than in Man, and as a general rule the first digit or
thumb is less developed and less freely movable. In the
genera Troglodytes and Simia, as in Man, the proximal
surface of the carpus articulates with the radius alone, in all
others it articulates also with the ulna. The scaphoid and
lunar bones are always distinct. An os centrale, (Gegen-
baur, Fig. 92, ce) is present in all, except in the Gorilla and
Chimpanzee, and some of the Lemurs. Where it is wanting
as an independent bone it probably has become fused with,
and then forms part of, the scaphoid. The pisiform is
present in all, and generally of a more elongated form, and
more salient than in Man : and there is usually a small

FIG. 92. — Bones of the carpus of a Baboon (fyiiocephalus anubis), J. s scaphoid ;
/ lunar ; c cuneiform ; p pisiform ; ce central ; rs radial sesamoid ; tin trapezium ;
td trapezoid ; in magnum ; it unciform ; I — v the metacarpals.

rounded radial sesamoid (rs) articulating movably to the
border of the scaphoid and trapezium, and connected with
the tendon of the flexor carpi radialis.

In the Potto (Perodicticus) there is an additional bone on
the palmar side of the carpus, an ossification in the ligament
connecting the palmar processes of the trapezium and
unciform bones, and forming with these processes a com-
plete bony ring, through which the flexor tendons pass.1

1 Mivart, " On the Appenclicular Skeleton of the Primates ; " Phil.
Trans. 1867.

XVI.]

CARNIVORA.

287

The metacarpals and phalanges are of the complete and
normal number in all, with the following exceptions. In the
African genus of Long-tailed Monkeys (Cclobus), and also in
the American Spider Monkeys (Ateles\ the thumb is rudi-
mentary, having usually but one very minute phalanx, in
addition to the metacarpal. In the Potto (Perodicticus) and
some allied Lemurina, the second (or index) digit is very
much shorter than the others, and has but two rudimentary
phalanges.

The phalanges are generally more curved than in Man,
most notably so in the Orang. The hand of the Mada-
gascar Aye- Aye (Chiromys) is remarkable for the extreme
attenuation of the bones of the third digit.

FIG. 93.-l!onesof the carpus of a lk-ar (Ursus anteriranus), }. si scapho-iunar
bone ; c cuneiform ; / pisiform ; ti unciform ; tit magnum ; td trapezoid ; ttn tra-
pezium ; rs radial scsamoid ; I — v the metacarpals.

In the CARNIVORA, the scaphoid and lunar bones always
coalesce into a single scapho-lunar bone (Fig. 93, sl\ with
which the centrale is united, the latter never appearing1 as
a distinct bone, except sometimes in very young animals.
The radial accessory ossicle or sesamoid (rs) is generally
present. All have five digits, with the complete complement
of phalanges, except the Hyaena, in which genus the pollex

1 See B. G. Wilder, " On the Composition of the Carpus in Dogs."
Bull. Cornell University, vol. i. p. 301, 1874.

288 7 HE MAN US. [CHAP.

is represented only by a rudimentary metacarpal. This digit
is usually much reduced in size, and often, as in the Dog,
does not reach the ground in walking. It is best developed
in the Bears and allied forms. The first metacarpal is never
more freely movable than any of the others. As a general
rule the middle digit is somewhat the longest, the second
and fourth nearly equal to it, the fifth shorter, and the first
the shortest.1

As the toes are nearly always armed with large, strong,
curved, and sharp claws (see Fig. 94), the ungual phalanges

i<;. 94. — The phalanges of the middle digit of the manus of the Lion (Fells led). I.
///' proximal phalanx ; //r middle phalanx ; flfi ungual phalanx ; a the central
portion forming the internal support to the horny claw ; /'the bony lamina reflected
around the base of the claw.

are large, strongly compressed, and pointed, and they
develop from their base a broad thin lamina of bone (/>),

1 The fissiped Carnivora have been divided into two groups, accord-
ing to the position of the feet in walking — the Plantigrade, or those
that place the whole of the palmar and plantar surface to the ground ;
and the Digitigrade, or those that walk only upon the phalanges, the
metacarpals and metatarsals being vertical and in a line with the fore-
arm or leg. This distinction, however, is quite an artificial one, and
every intermediate condition exists between the extreme typical planti-
grade gait of the bears and the true digitigrade action of the cats and
dogs. In fact, the greater number of the Carnivora belong to neither
of these groups, but maybe called "subplantigrade," often, when at
rest, applying the whole of the sole to the ground, but keeping the heel
raised to a greater or less extent when walking.

xvi.] CARNIVOKA. 289

which is reflected over the root (a) of the horny claw, and
holds it more firmly in its place. In those genera, as Felts,
in which the claws are retractile, the middle phalanx (ph'}
is deeply hollowed on its ulnar side to receive the ungual
phalanx when folded back upon it, in the quiescent state of
the foot.

In the Pinnipedia, the manus is broader and flatter
than in the terrestrial Carnivora. The scaphoid and lunar
coalesce. The ulnar side of the carpus is much reduced,
the unciform being especially small, and consequently the
fifth metacarpal articulates partly with the cuneiform of the
proximal row of the carpus. The pisiform is small. The
first digit is nearly as long as the second ; the remainder
gradually diminish in length to the fifth. The ungual pha-
langes in the ordinary Seals are slender, pointed, slightly
curved, and not much compressed. In the Otariidtc they are
prolonged beyond the part which bears the very small claw,
and flattened and truncated at the ends, being continued
onwards in the living animal as cartilaginous rays, which
support lobed expansions of the skin.

Among the INSF.CTIVORA, the scaphoid and lunar coalesce
in Galfopithecus, Ttipaia, CtnMes, Solenodon, Erinaceus, and
Gymnura, but in most of the other forms these bones are
distinct. A distinct os centrale is found in all except
Galeopithect4S, Potamogale, Chrysochloris, and Sorex.

There are nearly always five digits, but Rhynchocyon,
Oryzoryctes tctradactylus and Chrysochloris have but four,
the pollex being absent. The whole hand is generally
of moderate size, with pointed, conical, slightly curved,
ungual phalanges.

In common with every segment of the anterior extremity,
the manus of the Mole (Talpd) and its immediate allies is
extremely modified to suit its fossorial habits (see Fig 95).

290

THE MANUS.

[CHAP.

It is extremely broad and strong, its breadth being increased
by the great development of the radial sesamoid (rs), which,
being sickle-shaped, has received the special name of os
faldforme. The ungual phalanges are very large, and cleft
at their extremities

FIG. 95. — Bones of fore-arm and manus of Mole (Talpa europccd) X 2. R radius
U ulna ; s scaphoid ; / lunar ; c cuneiform ; p pisiform ; « unciform ; m magnum :
id trapezoid ; tin trapezium ; ce central ; rs radial sesamoid (falciform) ; i — v ihc
digits.

In the CHIROPTERA, the hand is especially modified in a
totally different manner, constituting the organ of flight.

In the carpus the scaphoid and lunar are united, and in
some genera (as Ptcropus) the cuneiform is joined with them,
so that the proximal row contains but a single bone. There
is no centrale. The pisiform is very small.

XVI.]

CHIROPTERA.

291

The pollex is short, divaricated from the other digits, not
enveloped, as they are, in a cutaneous expansion, and armed
with a curved claw. The other digits are extremely long and
slender.

In the Frugivorous Rats (Fteropida) the second digit has a
short ungual phalanx and claw, but in each of the other

*i

Fit;. 96. B^nes of the manus of Beaver (Castor canadensis), j.

digits the middle phalanx is elongated, and gradually tapers
to the termination, the ungual phalanx being absent.

In the Insectivorous Bats, the pollex alone has a claw,
and the elongation of the other digits is chiefly due to the
metacarpals, the phalanges being small and very slender,
and usually only two in number, except in the third digit,
which occasionally (as in Phyllostomida J) has three.

' G. E. Dobson, " Catalogue of Chiroptera," Brit. Mus.'i878.
U 2

292

THE MANUS.

[CHAP.

In the RODENTIA, the scaphoid and lunar are very
generally united (as in Castor, Dasyprocta, Hydrochcems,
Capromys, Sciurus, Arctomys, Mus, &c.), but not in all. An
os centrale is present in many, as Lepus, Dasyprocta, Hydro-
choerus, Capromys, and Castor, while in other genera it is
absent. There is very frequently an accessory ossicle on the
radial side of the carpus, which is particularly large in the
Beaver (Fig. 96). There are nearly always five digits, with

\s

FIG. 97. — Bones of the manus of Cape Hyrax (Hyra.v capensis), nat. size.

the normal number of phalanges, though sometimes (as in
Hydrochcenis} the pollex is rudimentary or suppressed.

HYRAX and the ELEPHANTS, together with various extinct
forms (Dinoceras, Coryphodon, Toxodon, &c.), are united
by Professor Cope under the name of Subungulata, in
opposition to the Ungulata vera. In all of these the
bones of the proximal and distal rows of the carpus retain
their primitive or more typical relation to each other. The

XVI.]

PROBOSCIDEA.

293

os magnum of the second row articulates mainly with the
lunar of the first, or with the cuneiform, but not with the
scaphoid. The axis of the third toe passes therefore through
the os magnum and through the os lunare.

In the Cape Hyrax (Fig. 97) there is an additional carpal
hone («), which is probably the os centrale, though in

IV

FIG 98.— B^nes of the manus of Indian Elephant (Elefhas indicm\

form and situation it looks as if it were a dismemberment
of the proximal part of the trapezoid. The scaphoid and
lunar are not united, and there are five digits, of which
the first is extremely small, and has only one minute
nodular phalanx. In another species, H. dorsalis, the pollex

294 THE MANUS. [CHAP.

is reduced to a short metacarpal ; the fifth digit has but
two phalanges, and the centrale is united with the trapezoid.
The ungual phalanges of the three middle digits are small
and somewhat conical in form.

In the Elephant (Fig. 98) the manus is short and broad,
the carpal bones are massive and square, and articulate by
very flat surfaces ; they consist of scaphoid, lunar and cunei-
form, a pisiform and the usual four bones of the distal row?
all distinct, without the centrale. There are five digits, with
short stout phalanges, the terminal ones being very small
and of irregular form.

All the existing true Ungulate Mammals agree in the
complete suppression of the pollex, in the absence of
an os centrale, and in the complete separation of the
scaphoid and lunar. The carpus is very compact, the bones
being generally more or less square, and articulating by flat
surfaces with each other, and with the radius and ulna
above. The second or distal row of the carpal bones has,
in comparison with the Subungulata, been shifted altogether
towards the radial side of the limb, so that the os magnum
is brought considerably in relation with the scaphoid, and is
entirely removed from the cuneiform as in the great majority
of existing Mammals. The axis of the third toe passes
therefore through the os magnum but between the lunar
and scaphoid. The Ungulata are eminently digitigrade, the
limb being (except in the Tylopoda] entirely supported on
the ungual phalanges, which are large, and encased in a hoof.

The digits are arranged according to one or the other of
two distinct types, each characteristic of, and giving name
to, one of the sub-orders.

i. The Perissodactyla, or " odd-toed " Ungulates, have the
middle or third digit the longest, and symmetrical in itself,
the free border of the ungual phalanx being evenly rounded.

XVI.]

FERISSODACTYLA.

295

The second and fourth toes may be subequally developed, as
in the Rhinoceros (Fig. 100), or they may be represented
only by mere splint like rudiments of their metacarpals, as in
the Horse (Fig. 101). All intermediate conditions are met
with in various extinct forms, as Palaotherium, Anchitherium,

F,G. 99.

FIG. loo.

FIG. 101.

FIG. 99. — Bone* of the manus of Tapir (Tapirus indicus), {.
FIG. loo. — Bones of the nianus of Rhinoceros (Rhinoceros sHinatrrnsis), \.
Fi<;. tot. --Bones of the manus of Horse (Equus catalius), J. Hand iv rudimentary
metacarpals.

and Hipparion. In the Tapir (Fig. 99) there are four
complete toes, in consequence of the fifth being developed,
though it scarcely reaches the ground in walking. In other
respects the foot resembles that of the Rhinoceros, the third
toe being longest, and symmetrical in itself and having on

296 THE MANUS. [CHAP.

each side of it the nearly equal second and fourth. In the
Rhinoceros there is a rudiment only of the fifth metacarpal.

In the Horse (Fig. 101), the three bones of the first row
of the carpus are subequal. The second row consists of a
very broad and flat magnum (;//), supporting the great third
metacarpal, having to its radial side the trapezoid (td), and
to its ulnar side the unciform (?/), which are both small, and
articulate distally with the rudimentary second and fourth
metacarpals. The pisiform is large and prominent, flattened
and curved ; it articulates partly to the cuneiform, and
partly to the lower end of the radius. The single digit
consists of a moderate-sized proximal, a very short middle,
and a wide, semilunar, ungual phalanx. There is a pair of
large nodular sesamoids behind the metacarpo-phalangeal
articulation, and a single, transversely extended, " navicular "
sesamoid behind the joint between the second and third
phalanx.1

2. The Ariiodaetyla have the third and fourth digits
almost equally developed, and their ungual phalanges
flattened on their inner or contiguous surfaces, so that each
is symmetrical in itself, but when the two are placed together
they form a figure symmetrically disposed to a line drawn
between them. Or, in other words, the axis or median
line of the whole manus is a line drawn between the third
and fourth digits, while in the Perissodactyles it is a line
drawn down the centre of the third digit.

In the S/iina, Pigs (Fig. 102), Peccaries, and Hippopotamus,

1 With reference to the interesting cases of atavistic polydactylism,
see Gegenbaur's " Critical Remarks on Polydactylyas Atavism," Journ.
of Anat. and Physiol. xvi. p. 615 ; Boas, " Bemerkungen ueber die
Folydactylie des Pferdes," Morphol. Jahrb. x. p. 182. By far the
larger number of cases of polydactyly in the Horse as in other
Mammals, are merely due to a teratological multiplication of digits,
and are not reversions to an ancestral condition, as frequently supposed.

XVI.]

ARTIODACTYLA.

297

the second and fifth toes are well developed, though always
considerably smaller than the third and fourth, all four
metacarpal bones are distinct, and the manus is compa-
ratively broad. The second row of carpal bones in the
Pig consists of a small trapezoid, a moderate-sized magnum,

FIG. KM.

FIG. 103.

FIG. 104.

l\\

FIG. 102. — Bones of the manus of Pig (Sus scrofa), J.

f IG. 103. —Bones of the manus of Red Deer (Cervus elaphus), 1.

FIG. 104.— Bones of the manus of Camel (Cainelus bactrianus),

and a large unciform. In the Hippopotamus there is also a
trapezium.

In the ruminating sections of the sub-order (Figs. 103 and
104), the third and fourth metacarpals, though originally
distinct, become more or less conjoined, generally so as to

298 THE MANUS. [CHAP.

form what appears externally to be a single bone, though
traces of their separate origin always remain ; the two distal
articular surfaces are quite distinct, each supporting a digit.
The lateral (second and fifth) metacarpus and digits are
generally rudimentary, sometimes completely absent. Some-
times not even the hoofs remain, as in the Giraffe, Prongbuck
(Antilocapra), and some other Antelopes ; sometimes the
hoofs alone, as in the Sheep, and Ox, supported, it may be,
by irregular nodules of bone, rudiments of the ungual
phalanges. In the Deer the three phalanges are complete,
sometimes with the lower end of the metacarpal, tapering
above, and not directly attached to other parts of the
skeleton of the foot. In other species (as in Fig. 103),
rudiments of the proximal ends only of the metacarpals are
present.1

In the Tragulina these metacarpals are completely deve-
loped, and articulate with the carpus. In Ifyomoschus,
belonging to this section, the third and fourth metacarpals
commonly remain distinct through life, so that the manus of
this animal scarcely differs from that of one of the St/ina,

The Tylopoda, or Camels, differ considerably from the
true Ruminants in the structure of the fore-foot (see Fig.
104). In the carpus the trapezoid and magnum are distinct,
as in the Suina and Perissodactyla, whereas these bones are
confluent in the Pecora and Traguiina. There are no traces
of any metacarpals or digits, except the third and fourth.
The metacarpals of these are very long and, as in the Fecora,

1 The last-named condition occurs in most of the deer of the Old
World, the former in all the American deer, with A Ices, Rangifer,
Hydropotes, and Cafreoliis. See Sir Victor Brooke, " I'roc. Zoological
Society, 1874," p. 36.

Regarding the occasional indication of a trapezium in the Cen'idir,
see Baur : " Der Carpus der Paarhufer," Morphol. Jahrb. ix. pp. 599-
602.

xvi.] ARTIODACTYLA. 299

confluent throughout the greater part of their length, though
separated for a considerable distance at the lower end. The
distal articular surfaces, instead of being pulley-like, with
deep ridges and grooves, are simple, rounded, and smooth.
The proximal phalanges are expanded at their distal ends,
and the wide and depressed middle phalanges are imbedded
in a broad cutaneous pad, forming the sole of the foot, on
which the animal rests in walking, instead of on the hoofs,
as in other Ruminants. The ungual phalanges are very
small and nodular, not flattened on their inner or opposed
surfaces, and not completely encased in hoofs. These
characters are better marked in the true Camels than in the
Llamas.

In the animals constituting the order CETACEA, the manus
has undergone a special modification, being converted into
a simple, flattened, oval or falciform, usually pointed flipper
or paddle, showing externally no signs of division into
separate digits, nor any traces of nails or claws. The skele-
ton, however, consists, as in other Mammals, of a carpus,
metacarpus, and either four, or more commonly five, digits,
the great peculiarity of which is, that the number of pha-
langes is not limited to three, as in all other animals of
the class, but may extend even to twelve or thirteen.

In the Whalebone Wloales, a large portion of the
skeleton of the hand remains permanently cartilaginous, but
the cartilages composing the various carpal bones and pha-
langes are separated from each other by interposed tracts
of fibrous tissue, and sometimes by synovial cavities. Nodules
of bone are deposited in the centre of some of these
cartilaginous masses, and slowly reach the surface as the
animal attains maturity : there are commonly not more
than five such ossifications. The phalanges appear like
cylindrical or slightly flattened bony masses, with roughly

3oo THE MANUS. [CHAP.

truncated ends, set in a continuous rod of cartilage. In
this way a certain amount of flexibility and elasticity is
secured in the flipper, but beyond this there is no actual
motion between the various bones of which it is composed.

The manus of the Right Whale (Baliena mysticetus) is
comparatively short and very broad, having all five digits
present, and being also extended on the ulnar side by a
flattened cartilage projecting from the edge of the carpus,
representing the pisiform bone. In adult specimens there
are usually only three distinct ossifications in the carpus.
The numbers in the digits are respectively I. i, II. 4,
III. 5, IV. 4, and V. 3. In the Rorquals (Balanoptera)
the first digit is absent, and the manus is of an elongated
and narrow form. The carpus has five ossifications, and the
number of phalanges varies somewhat in different species.
In Megaptera, the phalanges are both numerous and long,
producing the remarkable form of manus characteristic of
the genus.

In the Odontocetes, the ossification of the skeleton of
the manus is usually more complete than in the Whalebone
Whales, the carpal bones generally coming in close contact
at their edges, and assuming a somewhat polygonal form.
The phalanges are also better ossified, often having epi-
physes at each extremity, and they are connected together
by imperfect synovial joints. They are always very much
flattened, and their extremities being truncated and their
sides nearly parallel, they are either square or oblong
in form. In size they gradually decrease to the end of
the digit, the last often consisting of minute nodules or
granules, so irregularly or imperfectly ossified, and so easily
lost in cleaning, that it is in many cases impossible, when
describing the skeleton of one of these animals, to give the
exact number of phalanges to each digit.

xvi.] CETACEA. 301

The determination of the homologies of the carpal bones
of the Cetacea with those of other Mammalia is beset with
difficulties, and has consequently led to some differences
of opinion among those anatomists who have attempted it.
Moreover every species appears liable to certain individual
variations, and sometimes the different sides of the same
animal are not precisely alike, either in the arrangement, or
even the number of the carpal ossifications.

The pisiform is occasionally represented by a small ossifi-
cation on the ulnar border of the carpus. Excluding the
above, the carpus of the Odontocetes appears rarely to con-
sist of more than six bones, three belonging to the proximal
and three to the distal row.1

The three bones of the proximal row are constant, and
may easily be identified as corresponding to the scaphoid,
lunar and cuneiform of human anatomy, or the radiate, in-
termedium, and ulnare of Gegenbaur. The middle one is
usually the largest and most thoroughly ossified.

The three bones of the distal row are generally represented
by distinct ossifications (corresponding apparently with the
trapezoid, magnum, and unciform) in the genera Hyperoodon,
Mesoplodon, Beluga, and Monodon.

In many cases (see Fig. 105) the bones of the distal row
of the carpus are reduced to two, which appear to corre-
spond best with the trapezoid and unciform, the magnum
being either absent or amalgamated with the trapezoid.2

The trapezium appears never to be present as a distinct

1 At the meeting of the British Association in 1885, Prof. Turner
exhibited the carpus of a Hyperoodon with five distinct bones in the
distal row. See " Journ. Anatomy and Physiology," October, 1885.

8 For the reasons for this determination (about which, however,
there is considerable doubt), see Flower, " On the Osteology of the
Sperm Whale " ; Trans. Zoological Society, vol. vi. p. 360.

302

THE MANUS.

[CHAP.

bone, although the first meta-
carpal so often assumes the
characters and position of a
carpal bone, that it may easily
be taken for it.

The cuneiform always di-
rectly supports the fifth meta-
carpal, and frequently some
part of the fourth. Moreover,
in those species in which the
ulnar side of the carpus is
greatly reduced, as Globice-
phalus, the fifth metacarpal is
even connected with the ulna.

In the Cachalot (Physeter}
many of the carpal bones, in
addition to the usual central
nucleus, have epiphysial ossifi-
cations developed in the peri-
phery of the cartilage, which
ultimately unite with the cen-
tral piece of bone.

All the Cetacea with teeth
have five digits, though the
first is usually rudimentary
and in close contact with the
metacarpal of the second.
G. 105.— Dorsal surface of bones of In some forms, as Fhysctcr,

right anterior limb of Round-headed TT , ,f , J,

Dolphin (Globicephalus me/as), ^. HyperOOdOH, M Oil 0(1 OH, BelUgd,

The shaded portions of the digits are j . jj, . 1 /n u

cartilaginous, id trapezoid or magnum. Jnid^ J. l(ltCintSt(l, and C//YY7, the

manus is short, broad, and

rounded at its distal extremity ; the digits being nearly
equally developed, spreading from each other, and without

I!

xvi.] CETACEA. 303

any excessive number of phalanges. In the Grampus (Oreo)
all the phalanges are broader than they are long.1 In the
round-headed Dolphins (Globicephalus, Fig. 105), on the
other hand, the manus is extremely elongated, narrow, and
pointed. This elongation is mainly due to the- great develop-
ment of ihe second, and, though to a less extent, of the
third digit ; the fourth and fifth being quite short, and
having but few phalanges. The number of phalanges (in-
cluding the metacarpals) in the different digits are respec-
tively I. 4, II. 14, III. 9, IV. 3, and V. i.

In the common Dolphin (Delphiwts) the manus has the
same essential form, though in a less exaggerated degree,
the numbers of the phalanges being I. 2, II. 10, III. 7,
IV. 3, and V. i. The digits are all in close contact.

Order SIRKNIA. — Though in external form, and in being
inclosed in an undivided integument, the terminal segment of
the fore limb of the animals constituting this order much
resembles that of the Cetacea, its skeleton is totally different.

The carpus is short and broad. In the genus Afanatus
the seven most usual bones of this region are all distinct,
though there is no pisiform. The trapezoid is very small
and placed almost on the dorsal surface of the trapezium.
The cuneiform is large, and supports the greater part of the
fifth metacarpal. In Halicore many of the bones of the
carpus usually coalesce ; thus the first row may consist of
two bones, a scapho-lunar and a cuneiform, and all the
bones of the second row may unite together.

In both genera the digits are five in number, with
moderately elongated and flattened phalanges, which are
never increased in number beyond the limit usual in the
Mammalia.

1 This genus is remarkable for the imperfect ossification of the carpal
bones.

304

THE MANUS.

[CHAP.

Among the animals constituting the order EDENTATA
there is great diversity in the structure of the fore-foot.
They agree, however, in wanting an os centrale, and (with
the exception of Mam's) in .the presence of distinct scaphoid
and lunar bones.

In the existing Sloths the whole manus is long, very
narrow, habitually curved, and terminating
in two or three pointed, curved claws, in
close apposition with each other, incap-
able, in fact, of being divaricated, so that
it is reduced to the condition of a hook,
by which the animal suspends itself to
the boughs of the trees among which it
lives.

The carpus is small, and articulates by
a smooth rounded surface with the lower
end of the radius. In the Three-toed
Sloths (genus Bradypus) it consists of dis-
tinct scaphoid, lunar, and cuneiform bones
in the first row, but usually of only two
bones in the second row, the unciform,
and a connate magnum and trapezoid, the
trapezium being generally ankylosed to
the rudimentary first metacarpal.1 There

FIG. 106.— Bones of the • •,, jj'T i j'i

right manus of the is a small rounded pisiform, but no radial

sesamoid. The first and fifth nietacarpals
are present in a rudimentary condition
but bear no phalanges. The three middle digits are nearly
equally developed. The proximal phalanges are extremely
short, and soon become ankylosed to the ends of the
metacarpals, so that in adult animals one of the usual bones
of the digit appears to be entirely wanting. The middle
1 See "Journal of Anatomy and Physiology," vol. vii. p. 255.

XVI.]

EDENTATA.

305

phalanges are long and compressed. The ungual phalanges
are also long, much compressed, gently curved, and pointed.
Bony laminae reflected from their bases encase and support
the roots of the claws.

In the Two-toed species (genus Cholaepus, Fig. 106), the
magnum and trapezoid are distinct. The functional digits

FIG. 107 — Manusof Great Anteater
(Myrmecophagii jutata), J.

FIG. 108. — Manus of Little Anteater
(Cyrlatuna didactylus), X 2.

are the second and third, and there are rudiments of the
first and fourth metacarpals, though not of the fifth. The
proximal phalanges (/') are extremely short, as in Bradypus,
but do not ankylose with the metacarpals. The ungual
phalanges are not so long as in Bradypus.

In the Anteaters (Myrmecophaga, Fig. 107), all the usual
carpal bones are distinct. The unciform supports the fifth

306 THE MANUS. [CHAP.

fourth, and a considerable part of the third, metacarpals.
The first digit is very slender, the second also slender,
with compressed phalanges of nearly equal length. The
third digit is immensely developed ; though its proximal
phalanx is extremely short, its ungual phalanx is so long
that the entire length of the digit exceeds that of the second.
The fourth has a long and rather slender metacarpal, and
three phalanges gradually diminishing in size, the ungual
phalanx being very small. The fifth has the metacarpal
nearly as long, but not so stout as the fourth, and followed
by two small phalanges, the last rudimentary and conical,
and bearing no nail.

The little Tree Anteater (Cydoturus didactylus, Fig. 108),
has a remarkably modified manus. The third digit is greatl)
developed at the expense of all the others ; it has a stout,
short metacarpal, and but two phalanges, of which the most
distal is large, compressed, pointed, and much curved,
bearing a very strong hook-like claw. The second digit
has the usual number of phalanges and bears a claw, but
is very much more slender than the third. The fourth is
represented only by a styliform metacarpal, and one small
phalanx without a claw. The first and fifth metacarpals are
present but quite rudimentary. The pisiform is very large.
The trapezoid, magnum and unciform often coalesce.

In the Armadillos (Dasypodidce), the manus is stout and
broad, with strongly developed ungual phalanges, adapted
for digging and scratching. The fifth metacarpal articulates
with the cuneiform as well as the unciform. There is always
a very large palmar sesamoid. The digits are almost always
five in number, but vary much in relative si/.e and structure.

In the six-banded Armadillos (genus Dasypus), all the
digits have the normal number of phalanges (see Fig. 109).
The first digit is rather short and especially slender ; the

XVI.]

EDENTATA.

307

second is the longest, and has all the phalanges, as well as
the metacarpal, of nearly equal length ; the third has a long
metacarpal, then two short broad phalanges, the first being
especially short, and a long, curved, compressed, ungual
phalanx. The fourth and fifth are shorter, but present

FIG too. - Bones of the ri?ht manus of FIG. no.— Bones of the manus of the

the Hairy Armadillo (Dasyfus villa- Great Armadillo (Prioiion giganteus\

s\ 2 4- a an accessory carpal ossicle in front

of the pisiform, which is not seen in
the figure.

the same general characters, and their metacarpals are also
reduced in length.

All the deviations from the normal type of manus ob-
served in the common Armadillos, when greatly exaggerated
produce the curiously modified condition seen in the Cabas -
sou (Xcnurus unitindus). The first and second digits are
still more slender and elongated, and retain the normal

x 2

308 THE MANUS. [CHAP.

number of phalanges ; but in the other three the metacarpal
is short and broad, the proximal phalanx is either sup-
pressed or incorporated with the metacarpal, as in some of
the Sloths, the middle phalanx is very short, but the ungual
phalanx is enormously developed, larger in the third than in
the fourth and fifth digits.

A still further modification of the same type is seen in
the extraordinary mantis of the great Armadillo (Priodon
giganteus], the largest existing member of the group (Fig.
no). The metacarpals of the three outer toes are still
further reduced in length, the ungual phalanx of the third
is increased in size, while that of the fourth, and especially
the fifth, are greatly diminished.

In the genus Tolypentes the manus is formed on a some-
what similar type, except that the first digit is suppressed ;
but in the Nine banded Armadillos (genus Tatusia) it is
altogether different, the second and third toes being subequal
(the third the longest), with moderate, conical, and slightly
compressed ungual phalanges : and the first and fourth
also nearly equal and smaller, all with the normal
number of phalanges. The fifth is absent, or (as in
T. hybrida) represented by three very rudimentary nodular
bones.

In the Pangolins (Manis) the scaphoid and lunar are
united but all the other carpal bones are distinct. There
are five digits with the complete number of phalanges, which,
except in the pollex, are short and broad. The distal ends
of the ungual phalanges have deep median clefts. This
phalanx in the third digit is immensely developed, and con-
siderably so in the fourth. The first, second, and fifth digits
are comparatively small.

In the Cape Anteater (Orycteropus) the pollex is entirely
suppressed, but all the other digits are well developed, and

xvi.] EDENTATA. 309

terminate in subequal, compressed, ungual phalanges of
moderate size. The second and third digits are nearly
equal, the fourth and fifth shorter. A sesamoid bone is
developed on the dorsal side of the metacarpal-phalangeal
articulations.

Order MARSUPIALIA. — The carpus never has a distinct
os centrale. It is commonly stated that there is a scapho-
lunar bone ; but the lunar, though always small, is distinct
in Didelphys, Perameles, Dasyurus, Thylacinus, Phalangista,
and Hypsiprymnus (where it is very minute) ; and its ab-
sence in Macropus appears to be due rather to suppression
than to coalescence with the scaphoid. In Phascolomys a
small lunar is present in some individuals, and not in others.

With the exception of the genus Chceropus, all known
Marsupials possess the normal number of digits and pha-
langes, and the manus is short and rather broad, with
moderately developed, compressed, curved, ungual pha-
langes.

The little " pig- footed " insectivorous Marsupial, Chotropus
castanotis, belonging to the family Peranulida, has a remark-
ably modified manus (see Fig. 112) in which only two
digits are functionally developed ; and as the metacarpals
are very long, and closely pressed together (though not
ankylosed), and the phalanges are short, and the nails rather
hoof-like, the whole manus has much general resemblance
to that of the Artiodactyle Ungulates. It presents, how-
ever, the essential difference that the functional digits are
the second and third of the normal series, instead of the
third and fourth. This is proved by comparing it with
the less modified manus of a true Perameles (Fig. in).
The principal changes from the typical Mammalian manus
observed in Perameles are the great reduction of the
first and fifth digits; while the second, third, and fourth

THE MANUS.

[CHAP.

remain functional, with long ungual phalanges cleft me-
sially at their extremities. The third is longer than the
second, and this longer than the fourth. In Chceropus
the second and third remain, and retain their relative
size, though comparatively longer, more slender, and
with smaller ungual phalanges. The fourth digit is

Fit;, in. — Bones of manus of Bandicoot Fro. 112. — Hones of manus of Chccrof>u
(J't-rame/cs), X i$. castanotis, X 2.

rudimentary, but with the normal number of phalanges ;
the first and fifth are entirely suppressed. The carpal
bones have their normal relations, but the trapezium is
exceedingly reduced.

Order MONOTREMATA. — In the Echidna the carpus is
short and broad, and has a very complex articulation
with the distal ends of the radius and ulna. The first row

xvi.] MONOTREMATA. 311

consists of a scapho-lunar and a cuneiform. There is no
central. The dibtal row has the usual four bones. The
pisiform is large, and articulates with the ulna as well as the
cuneiform, and there is a small radial sesamoid, articulating
with the scapho-lunar. There are also two large sesamoids,
sometimes united, in the palmar tendons. The digits are
five in number, all with the normal number of phalanges,
which are short and broad, except those that bear the
long, slightly curved, broad nails, with which the animal
scratches and burrows in the ground. The pollex is more
slender than the other digits ; it is of about the same length
as the fifth, the second and fourth are nearly equal and
longer, and the third slightly the longest.

In the Ornithorh)nchus the manus is comparatively more
slender and elongated ; but the number and arrangement
ot the bones are the same as in the Echidna.

CHAPTER XVII.

THE PELVIC GIRDLE.

THE posterior limb consists of a pelvic girdle and three
segments belonging to the limb proper, viz. the thigh, the
leg, and the foot, or pes.

The PELVIC GIRDLE is present in some form in all Mam-
mals, though in the Cetacea and the Sirenia it is in an
exceedingly rudimentary condition.

In all Mammals, except those belonging to the two
orders just named, each lateral half of the pelvic girdle
consists primitively, like the corresponding part of the an-
terior limb, of a rod of cartilage crossing the long axis of
the trunk, having an upper or dorsal, and a lower or ventral,
end. The upper end diverges from that of the opposite
side, but the lower end approaches, and, in most cases,
meets it, forming a symphysis, without the intervention of
any bone corresponding to the sternum.

The pelvic girdle differs from the shoulder girdle in being
articulated to the vertebral column, at a point near to, but
not at, the upper end of the rod.

Like the shoulder girdle, it bears on its outer side, near
the middle, a cup shaped articular cavity (acctabulum or
cotyloid cavity, Fig. 113, a, p. 313), into which the proximal
extremity of the first bone of the limb proper is received.

CH. XVII.]

GENERAL CHARACTERS.

313

Like the shoulder girdle it is divided, by its mode of
ossification, into an upper (dorsal) and a lower (ventral)
segment, and the point of union between these is near the
middle of the articular cavity.

Unlike the shoulder girdle of most Mammals, the lower
segment is always largely developed, and ossifies from two
separate centres, which form an anterior and a posterior

••

KlG. 113. — External surface of right innominate bone of a young Lamb (Ovfs arits),
J. // ilium (gluteal surface); j/ supra-iliac border ; ah acetahular border ; /^ischial
border ; /s ischium ; s/> spine ; /;' tuberosity of ischium ; /".pubis ; s symphysis ;
M_/ thyroid or obturator foramen : « acetabulum.

bar, in contact above and below, but leaving a space
between them in the middle, filled only by membrane, and
called the thyroid or obturator foramen (//</).

The upper segment is named the ilium (//), the anterior
bar of the lower segment the pubis (/*), and the posterior
bar the ischium (Is). In the process of growth these three

314 THE PELVIC GIRDLE. [CHAP.

osseous pieces always coalesce into a single bone, called the
os innominatum.

This is further completed by the addition of epiphyses ;
one for the upper extremity of the ilium (corresponding to
the supra-scapular epiphysis of the shoulder), and others for
the most prominent parts of the lower or free borders of the
pubis and ischium (symphysis pubis and tuber ischii).

In most Mammalia (perhaps with the exception of the
Monotremata, Lemuroidea and Chiroptera) a fourth pelvic
bone is found, situated between the ilium, pubis, and ischium.
This, the so-called os acetabuli^- either persists as a separate
ossification (it is especially large in Talpa, Sorex, Viverra,
and Lepus) or it fuses with one of the three other pelvic
bones. Its morphological meaning is as yet unknown, but
it can scarcely be considered as an epiphysis.

The three principal bones of the pelvis nearly always
enter into the formation of the acetabulum, but in a few
genera, as Lepus, \\\e pubis is excluded.2

There is never any secondary osseous bar in the pelvic
girdle corresponding to the clavicle of the upper extremity.

The ilium of Mammals is essentially an elongated, three-
sided, or prismatic bone, though the relative size and posi-
tion of the various surfaces and angles may differ greatly
in different species. In the most characteristic form, one
of the surfaces is internal, or directed towards the ver-
tebral column, articulating by a flat irregular surface with the
lateral " pleurapophysial " ossifications of the sacral vertebrae.

1 See W. Krause, " Ueber den Pfannenknochen," Centralblatt f.
d. medicinisch. \Vissenschaft. 1876, No. 46 ; W. Leche, " Zur
Anatomic der Beckenregion bei Insectivora." K. Svenska Vetensk. ;
Akad.'s Handlingar, xx. 1883 ; and Bronn's " Clas en und Ordnungen
des Thierreichs, Mammalia."

2 Gegenbaur, " Ueber den Ausschluss der Schambeines vom Hueft-
gelenk," Morph. Jahrb. 1876.

xvii.] GENERAL CHARACTERS. 315

This may be called the sacral surface (see Figs. 114, and
Ir5. P- 3X7; and 116, ss, p. 325.) Another is directed
mainly forwards, and may be called anterior or iliac (M), as
it gives origin to the iliacus muscle. The third is posterior
or gluteat (gs), as it gives origin to the gluteal muscles.

Of the borders one is external or acetabular (ab\ as it
ends below at the margin of the acetabulum ; another is
antero-internal or pubic ( pb), and the third is postero-internal
or ischial (ib)t so called because they end below by joining
the pubis and the ischium respectively.

The innominate bone is always placed more or less
obliquely to the vertebral column, the upper or iliac end
inclining forwards, and the lower or ischio-pubic end turning
backwards, contrary to the usual direction of the scapular arch.
In order to give still greater stability and fixity to the pelvic
girdle, and to incorporate it more completely for mechanical
purposes with the vertebral column, there is, in addition to
the articulation between the ilium and true sacral vertebrae,
a very strong double ligamentous union between the ischium
and the side of the anterior caudal or pseudo-sacral vertebrae,
constituting the greater and lesser sacro-sciatic ligaments,
which are replaced in some Mammals (as most of the Eden-
tata) by a complete bony union.1

The two innominate bones, together with the sacrum,
constitute the pelvis, a complete circle of bone, or rather a
short tube. This has two outlets : an anterior (sometimes
called inlet or brim) bounded by the inferior surface of the
first sacral vertebra above, by the pubic borders of the
ilia laterally, and by the anterior borders of the converging
pubic bones, meeting at the symphysis below ; and a

1 Practically, though not morphologically, the pelvis is a part of the
trunk or axial skeleton. The functions of the hind limb in propelling
and raising the body necessitate that it should be so.

316 THE PELVIC GIRDLE. [CHAP.

posterior outlet, bounded by the posterior part of the
sacrum above, by the great sacro-sciatic ligaments laterally,
and by the converging posterior borders of the ischia below.
In consequence of the oblique position of the innominate
bones, the plane of the anterior outlet (in the horizontal
position of the body) looks downwards and forwards ; that
of the posterior outlet upwards and backwards ; but these
two planes are not exactly parallel, the long axis of the
cavity being usually more or less curved.

Modifications of the Pelvic Girdle in the different Groups
of Mammalia.1

Order PRIMATES. — The pelvis of man is very consider-
ably modified from the usual form met with in Mammals.
The innominate bone (Fig. 114) is remarkably broad in
proportion to its length. The ilium is flattened and ex-
panded, and has a greatly extended, almost semicircular
supra-iliac border (si). The sacral surface (ss) is small, and
scarcely rises above the vertebral attachment. The iliac
surface (is) is very broad and hollowed. The gluteal surface
is likewise much expanded, and, though presenting several
curves, is, in the main, convex. The acetabular border (a/>)
is veiy short, and lias a strong, rounded, rough prominence
for the attachment of the tendon of the rectus (extensor)
muscle of the leg. The pubic border (pl>) is slightly
marked, constituting the linea arcuata interna, or linca ilio-
pectinca of human anatomy. The ischial border (//;) is
short and deeply hollowed. The acetabulum (a) is large,
circular, with very prominent borders, incomplete only for a
small space on the infero-internal aspect.

1 See Weyhe, " Uebersicht der Saeugethiere nnch ihren Eecken-
formen, "Zeitschr. f. d. gesammten Natun\iss. xi. iS75.

XVII.]

PR IMA TES.

317

The pubis and ischium are short, and widely divergent
from each other, so that the thyroid foramen (////") is elon-
gated in the direction across the main axis of the bones.
The symphysis (s) is rather short, and formed by the
pubis alone. Each of the apposed surfaces of bone is

rff

KIG. 114. — Ventral surface of right inno-
minate bone of Man, i

FIG. 115. — Ventral surface of right inno-
minate bone of Dog, J.

it supra-iliac border or crest of the ilium ; s.t sacral surface ; is iliac surface ; ab
acetabular border ; pb pubic border ; ib ischial border of ilium ; a acetabulum ;
My thyroid or obturator foramen ; /»' toberosity of ischium ; * symphysis of pubis.

capped by a plate of nbro-cartilage ; these are held to-
gether by strong ligamentous fibres, while between them
there is usually a more or less perfect synovial cavity.
Ankylosis at this spot, so common in the lower Mammalia,
very rarely takes place in Man.

3i8 THE PELVIC GIRDLE. [CHAI-.

The posterior and inferior border of the ischium is thick-
ened and rounded, and distinguished as the tuber ischii (//).
Above this, on the hinder border of the same bone, is a
smooth, hollowed surface, called the lesser sciatic notch,
surmounted by an angular prominence called the spine ;
above the spine the edge of the ischium passes into the
great concavity of the posterior or ischial border of the
ilium, and which is called the great sciatic, or, more pro-
perly, ilio-ischiatic notch. The strong ligaments (sacro-
sciatic) which pass from the side of the pseudo-sacral and
caudal vertebrae, the one to the tuber and the other to the
spine of the ischium, convert these notches in the living
body into foramina.

The anterior or superior (in the vertical position) outlet of
the pelvis is subcircular, usually rather broader from side to
side than from the vertebral to the pubic border. Its plane
is not far from a right angle with the axis of the vertebral
column. The posterior outlet is also very wide. In con-
sequence of the great curve of the sacrum, and the short-
ness of the symphysis, the axis of the whole pelvis is
strongly curved.

In all the Simiina the innominate bone, especially the
iliac portion, is more elongated than in Man ; the anterior
outlet of the pelvis is longer from above downwards, nar-
rower, and more oblique; the tuberosities of the schia
are more everted, and the spine and sciatic notches less
marked.

In the highest forms, such as the Gorilla and Chimpanzee,
the upper part of the ilium is expanded, flattened, and
everted, the iliac surface being even wider than in Man,
though much flatter ; but in the Baboons and Monkeys,
the whole ilium is long and narrow, the sacral surface rises
considerably above the sacral articulation, the iliac surface

xvn.J CARNIVORA. 319

is narrow, the gluteal surface is very hollow, and the borders
all approximate to straight and {arallel lines. In the Old-
World monkeys the tuberosities of the ischia are greatly
everted, and terminate in broad, triangular, flattened, rough
surfaces, to which the ischial cutaneous callosities are
attached.

In the true Lemurs the pelvis is very wide ; the ilia are
long, narrow, and have a sigmoid curve, while the pubes
approach each other at the symphysis at a very open angle,
giving an elegant lyre shape to the anterior outline of the
pelvis. On the other hand, in the genus Loris of the same
group (and to a less extent in Tarsius, Perodicticus, and
others) the cavity of the pelvis is remarkably narrow from
side to side ; the ilia are straight slender rods, from the
lower end of which the large, flattened, and compressed
pubes project forward at a right angle, forming a prominent
keel at the symphysis.

In the CARNIVORA the pelvis is generally elongated and
narrow, the ilium and ischium being in a straight line, and
of nearly equal length. In most species the ilia are straight,
flattened, and not everted above (see Fig. 115, p. 317), the
iliac surface (is) is very narrow, and confined to the lower
part of the bone, as the acetabular and pubic borders meet
in front above ; the gluteal surface looks directly outwards
and is concave ; the sacral surface (ss) forms a broad flat
plane above the attachment to the sacrum, the crest being
formed by the united edges of the sacral and gluteal sur-
faces, instead of the iliac and gluteal surfaces, as in Man.
The symphysis is long ; it includes part of both pubis and
ischium, and commonly becomes completely osseous in
adult animals. The thyroid foramen (//{/) is oval, with its
long axis parallel to that of the whole bone. The ischia are
wide and divergent posteriorly.

320 THE PELVIC GIRDLE. [CHAP.

In the Hyasna the pelvis is shorter and wider than in most
other Carnivora, both the upper ends of the ilia and lower
ends of the ischia being considerably everted.

In the Bears the ilia are short and everted above.

In the Seals the pelvis is small, and of a different form
from that of the terrestrial Carnivora. The ilia are exceed-
ingly short, and with much everted upper borders ; the
pubes and ischia are very long and slender, inclosing a long
and narrow obturator .foramen, and meeting at a symphysis
of very small extent, in which the bones of the two sides
are very slightly connected, and capable of being widely
separated during parturition.

The pelvis of the INSECTIVORA varies considerably in
form. In Galeopithecus, Rhynchocyon, Macroscelides and
Tupaia, the symphysis is long, as in the Carnivora, and
becomes ankylosed ; in Erinaceus, Centetes, Potamogale, and
Myogale, it is short, though the bones of the two sides are
in contact, but in many other genera, e.g. in Talpa, Chry-
sochloris and Sorex, the pubic bones are widely separated in
the middle line below.

The Mole has an exceedingly long, narrow, and straight
pelvis, the innominate bones lying almost parallel with the
vertebral column. Both ilium and upper end of the
ischium are firmly ankylosed with the sacrum, leaving a
small sacro-sciatic foramen between them, but the pubic
bones do not quite meet in the middle line below. The
pubes and ischia are very long and straight, and inclose a
large, but narrow, oval thyroid foramen.

In the CHIROPTERA, the pelvis is small and narrow ; the
ilia are rod-like, the pubes and ischia are not in a line with
them, but project forwards. In most species the pubic
bones of the opposite sides are very loosely united in front
in males, and in females they are widely separated ; in the

CHIROPTEKA. 321

Rhinohptuda alone do these bones form a symphysis
(Dobson). There is usually a strongly developed " pectineal "
process, near the acetabular end of the anterior border
of the pubis, and which in some genera (e.g. Phyllorhina,
triienops), is prolonged so far as to unite with a process from
the superior extremity of the ilium, forming a pre-acetabular
foramen, as large as, or larger than, the thyroid foramen, an
arrangement unique among Mammals.

In many of the RODENTIA, as the Beaver, the ilia are
markedly trihedral, with sides of nearly equal extent; but
in the Hares the outer (acetabular) border is almost obso-
lete, the gluteal and iliac surfaces are confluent, and both
face outwards, and the internal surface is largely deve-
loped above the sacral attachment.

The pubes and ischia are always largely developed, flat,
and diverging posteriorly, the obturator foramen is of con-
siderable si/e, and the symphysis is long, and usually
becomcs osseous ; in the Guinea Pig (Cavia), however, it
remains ligamentous, and the bones are widely separated
during parturition.

Order UNGUI.ATA. — In the Pecora the pelvis generally is
elongated. The ilium is expanded and everted at the
upper extremity ; but between the sacral attachment and the
acctabulum it is much contracted, and its borders rounded,
so that the divisions of its surfaces are no longer distinct.
There is usually a deep oval depression above the ace-
tabulum, just within the attachment of the rectus femoris
muscle. The anterior outlet forms a regular oval with the
long diameter between the sacrum and symphysis. The
latter is very long, including a considerable portion of the
ischia. The margins of the bones are completed by large
epiphyses in this region, but ultimately coalesce across
the middle line. The ischia are much developed ; the

322 THE PELVIC GIRDLE. [CHAP.

tuberosities are large, and have on the middle of their outer
side a well-marked conical process, directed outwards, and
very characteristic of this group of animals.

In the Giraffe the pelvis is shorter than in most of the
other Pecora ; the upper ends of the ilia are more ex-
panded, the thyroid foramen is nearly circular, and the
supra-acetabular fossa is almost obsolete.

These characters are still more strongly marked in the
Camels ; while, on the other hand, in the Pigs the pelvis is
elongated, and much resembles that of the Pecora, but the
supra-acetabular fossa is wanting.

In the Perissodactyla, the ilia are widely expanded above,
but much contracted on approaching the acetabulum. The
ischia are less elongated than in the Pecora, and the thy-
roid foramen is more circular.

The Elephant has a very peculiar pelvis, the form of the
ilium and the arrangement of its surfaces somewhat recalling
those of the human pelvis. The supra-iliac border or crest
is greatly extended and curves outwards and downwards.
The sacral surface of the ilium is narrow, and scarcely rises
above the attachment to the sacrum. The iliac and gluteal
surfaces are widely expanded, especially at the upper part,
and, the pelvis being set nearly vertically to the vertebral
column, they face almost directly forwards and backwards.
The outer or acetabular border is short and deeply hollowed.
The pubic and ischial portions are comparatively small, the
latter being very little produced backwards beyond the
symphysis.

In the SIRENIA, the pelvis is extremely rudimentary, being
composed, in the Dugong, of two slender, elongated bones
on each side, placed end to end, and commonly ankylosing
together. The upper one, which represents the ilium, is
connected by a ligament with the end of the transverse

xvn.] SfKENIA. 323

process of the sacral vertebra, usually the fourth behind the
last that bears a free rib ; the lower one is the ischium, or
ischium and pubis combined, and approaches, though it
does not meet, its fellow of the opposite side.

In the adult Manatee, the innominate bone is represented
by a single irregular triangular bone, connected by rather
long ligaments with the vertebral column above, and with
the opposite bone across the middle line.

There is no trace of an acetabulum, or of any portion of
the limb proper in any of the existing Sirenia ; but in the
extinct Halitherium an acetabular depression and rudimentary
styliform femur have been discovered.

In the CETACEA the pelvis is reduced to a pair of elon-
gated slender bones (each of which ossifies from a single
centre), placed on each side of, and rather below, the ver-
tebral column, lying nearly parallel to its long axis (though
they converge somewhat anteriorly), and opposite the spot
where the chevron bones commence to be developed
beneath the bodies of the vertebrae. These bones probably
represent the ischia, and their principal function is to
give attachment to the crura of the penis or clitoris, as
the case may be. Hence they are usually more largely
developed in the male than in the female.

In the Whalebone Whales they usually have a project-
ing angle placed about the middle, near which, in some
species, a second small bone, which probably represents
the femur, is attached by ligament (see Fig. 120, p. 335).
In a full-grown male Rorqual {Balanoptera musculus),
sixty-seven feet in length, each pelvic bone was sixteen
inches long. In the Greenland Whale (Balczna mysticetus,}
they are rather shorter and stouter. As might be expected,
from the rudimentary character of these bones, they vary
considerably in size and form in different individuals of

Y 2

324 THE PELVIC GIRDLE. [CHAP.

the same species, and often on the two sides of the same
animal.

In the Dolphins, they are generally smaller, and more
simple than in the Whalebone Whales, and usually quite
straight, though sometimes arched, or presenting a sigmoid
curve. In Platanista alone no traces of pelvic bones have
yet been found.

Order EDENTATA. — In the Sloths, the pelvis is very short
and wide, with tolerably broad flattened ilia, and slender
pubes and ischia, inclosing a large oval thyroid foramen,
the inferior boundary of which, and the extremely narrow
ossified symphysis, are formed by the pubis alone. The
spine of the ischium is produced backwards to unite with
the transverse processes of some of the pseudo-sacral ver-
tebras, inclosing a sacro-sciatic foramen. The sacro-iliac
articulation is commonly ankylosed.

In all the other Edentates the pelvis is more or less elon-
gated, the ilia trihedral, the ischia largely developed, (he
pubes slender, the symphysis exceedingly short, but usually
ossified, and the thyroid foramen large. In all, except Oryc
teropus, the ischii unite with the vertebral column. This
union is carried to its greatest extent in the Armadillos, in
which animals the broad transverse processes of as many as
five pseudo-sacral vertebrae may coalesce with each other and
with the side of the ischium, converting the pelvis into a long
bony tube, the more so as the ilia are also firmly and exten-
sively united with the true sacrum. There is usually, especially
in Orycteropus, a strongly developed " pectineal " tubercle.

Order MARSUPIALIA. — In the American Opossums
(Didelphys), the ilium is a very simple, straight, three-sided
rod, thicker at its upper end than at its acetabular end,
each side being nearly equal in extent, hollowed, and sharply
defined by prominent straight borders.

XVII.]

MARSUPIALIA.

325

• In the Kangaroo (Macropus, Fig. 116), the three surfaces
of the ilium are also well marked and nearly equal : but the
whole bone is curved outwards at the upper end.

In the Thylacine and Dasyures the ilia are compressed
laterally, the acetabular and pubic
borders meeting above in front, so that
the iliac surface is (as in the Carnivora)
very narrow, and disappears in the
upper half of the bone, the "crest"
being formed by the united edges of
the sacral and gluteal surfaces ; where-
as in the wide, depressed pelvis of the
Wombat (Phascolomys\ the flattening
has taken place in the contrary direc-
tion, and the iliac surface spreads out

to form with the gluteal surface behind

a wide, arching, supra-iliac border and

crest.

The ischia and pubes are always

largely developed, and the symphysis

is long and generally ossified. In the

Kangaroos the pectineal tubercle (//)

of the pubis is strongly developed.
Nearly all Marsupials have a pair of

elongated, flattened, slightly curved

bones (Fig. 116, m\ movably articu-
lated by one extremity to the anterior

edge of the pubis, near the symphysis,

and, passing forwards, diverging from * symphysis: m -mar-

supial bone.

each other, within the layers of the
abdominal parietes. They are, in fact, ossifications in, or
intimately connected with, the inner tendon or " pillar " of
the external oblique muscle, and therefore come under the

ti

FIG. 116 — Ventral surface
of innominate bone of
Kangaroo (Mncropus
major), J. si supra-
iliac border ; ss sacral
surface ; is iliac sur-
face ; al> acetabular bor-
der ; pb pubic border of
ilium ; // pectineal tu-
bercle ; a acetabulum ;
////"thyroid foramen ; //'
tuberosity of ischium ;

326 THE PELVIC GIRDLE. [CH. xvn.

category of sesamoid bones. They vary in size and shape
in different species. In Didelphys they are nearly as long
as the ilia, while in the Kangaroo they are scarcely half the
length of that bone. Though largely developed in the
Dasyures, in the allied genus Thylarinus they are repre-
sented only by small, unossified fibro-cartilages.

These bones are commonly called " marsupial bones,"
though they have no special function relating to the ventral
pouch of the female, being nearly equally developed in both
sexes, and also in those species in which the marsupiurn is
not present.1

In the MONOTREMATA the pelvis is short and broad.
The ilia are short, distinctly trihedral and everted above.
The ischia are large, and prolonged into a considerable
backward-directed tuberosity. The symphysis is long, and
formed about equally by pubes and ischium. The thyroid
foramen is round. The acetabulum is perforated in Echidna
as in Birds, but not in Ornithorhynchus. The pectineal
tubercle is greatly developed. There are large " marsupial "
bones in both genera.

1 See O. Katz, " Zur Kenntniss der Bauchdecke uncl der mit ibr
verkniipften Organe bei den Beutclthieren. Zeitschr. f. wiss Zoolog."
36, 1882, p. 6ll.

CHAPTER XVIII.

THE THIGH AND LEG.

THE skeleton of the first segment of the limb proper
consists of an elongated, more or less cylindrical bone,
the femur^ which is described as having a shaft and two
extremities.

The dorsal, or (in the ordinary position of the limb)
anterior surface of the shaft, is smooth and rounded from
side to side, and generally arched somewhat forwards from
above downwards ; the ventral or posterior surface is more
or less compressed, and has a rough longitudinal ridge, the
linta aspcra.

At the proximal extremity is a hemispherical, smooth,
articular " head " (Fig. 117, //, p. 328) which fits into the
aretabulum of the innominate bone, and is generally more
round and more distinctly separated from the rest of the
hone by a constriction or "neck" (//) than is the corre-
sponding part of the humerus. The axis of the head does
not coincide with that of the shaft of the bone, but crosses
it at an angle varying in different animals, being directed
towards the preaxial1 or (in the ordinnry position of the
limb) internal side, and slightly also towards the anterior

1 See note to p. 269.

328

THE THIGH AND I. EC.

aspect. In nearly all Mammals there is a rounded depres-
sion near the middle of the surface of the head into which
the Hgamentum feres of the hip-joint is inserted. Both
ligament and depression are, however, wanting in the (Drang
Utan, Seals, the Sea-Otter, Elephant,
Sloths, Wombat, and the Monotremata.
Immediately below the neck of the
femur are two tuberosities, called tro-
chanters. One (//) is a comparatively
small, conical eminence, situated rather
to the pre-axial side, and called the
lesser or inner trochanter. The other
(gf) is generally very prominent, pro-
jecting upwards, as high or higher than,
the top of the head, situated mainly
on the post-axial border of the bone,
but curving inwards and backwards at
its extremity; this is called the great
or outer trochanter. To the posterior
side of its base there is usually a deep
depression, the digital fossa.

In some Mammals, as the Perisso-
dactyle Ungulates, some Rodents and
Edentates, there is a compressed ridge
for attachment of the great gluteal
muscle on the post axial side of the
shaft, a short distance below the great
trochanter, distinguished as the third trochanter. (See Fig.
118, /', p. 333.)

The distal extremity of the femur is thickened, and has a
large trochlear articular surface for the bones of the leg.
This surface is narrow in front, and bounded by more or less
prominent ridges : posteriorly it is divided by a deep median

FIG. 117. — Right human
femur, d >rsal or ante-
rior aspect, \. The
boundary lines of the
various epiphyses are
shown. A head ; « neck ;
ft greater trochanter ;
ill lesser trochanter ; ec
external condyle ; ic in-
ternal condyle.

xvin.] GENERAL CHARACTERS. 329

notch (intercondylar) into two prominent rounded eminences,
called condyles (Fig. 117, cc and if). The slightly elevated
roughed portions of bone above the articular condyles are
termed the tuberosities.

The femur has a main centre of ossification for the shaft,
and epiphysial centres for the head, for each trochanter, and
for the lower extremity. (See Fig. 117.) In most Mammals
the great trochanter and head coalesce together before they
join the shaft. The lower epiphysis is the last to become
united.

The skeleton of the second segment of the limb consists
of two bones, the tibia and fibula? of which the former is
the larger in all Mammals. These bones always lie in their
primitive, unmodified position, parallel to each other, the
tibia on the pre-axial, and the fibula on the post-axial side
and are never either permanently crossed or capable of any
ronsiderable amount of rotation, as in the corresponding
bones of the fore-limb. In the ordinary walking position the
tibia is internal, and the fibula external.

The tibia has an expanded proximal end, with a flattened
articular surface, divided into two slightly concave facets, by
a rough median eminence, to which the intra-articular or
crucial ligaments of the knee-joint are attached. The shaft
is usually more or less trihedral, with one flat surface directed
backwards, and one border forwards. The upper end of
this border is thickened into a rough tuberosity, into which
the tendon of the great extensor muscles of the leg are
inserted. The lower end is slightly expanded, and has a
somewhat square articular surface to receive the proximal
bone of the tarsus, or astragalus. The inner (pre-axial) side
of the bone is prolonged beyond this surface, forming a

1 Also occasionally called perone, whence " peroneal," applied to
structures in relation with it.

330 THE THIGH AND LEG. [CHAP.

process called internal malledus, which is applied to the
side of the astragalus, giving additional strength to the
articulation called "ankle-joint."

The fibula has a slender and generally compressed shaft,
and is somewhat expanded at each extremity. Its upper
end usually takes no part in the knee-joint, being con-
nected, by a separate synovial joint, with the tibia just
below that articulation. The lower end, however, forms the
outer side of the ankle-joint, under the name of external
malleolus.

In many Mammals the fibula is in a more or less rudi-
mentary condition, and it often ankyloses with the tibia at
one or both ends.

As a general rule each of these bones has a principal
centre of ossification for the shaft, and an epiphysis at
either end.

In the neighbourhood of the knee-joint, certain sesamoid
bones are often found in connection with the tendons which
pass over the various bony prominences.

The largest and most constant is the patella, placed on
the anterior surface of the joint, in the conjoined tendon
of the four great extensor muscles of the leg, and having
a smooth articular facet, which plays upon the narrow
anterior part of the inferior articular surface of the femur,
and forms part of the wall of the cavity of the knee joint.
This bone varies considerably in form, being in some cases
broad, flattened, or lozenge-shaped, and in others, laterally
compressed or oval. It is found in an ossified con-
dition in all Mammals, with the exception of a few of the
Marsupialia.

There are also very frequently smaller ossicles, one
or two in number, situated behind the femoral condyles,
called fabclltc ; and occasionally there is a wedge-shaped

x v 1 1 1 ] rRIMA TES. 33 j

bone within the joint, lying on the articular surface of the
tibia, an ossification of the internal inter-articular semilunar
cartilage.

Special Characters of tht Bones of the Thigh and Leg in the
various Groups.

In Man, the femur (see Fig. 117, p. 328) is long and
rather slender, the shaft is curved forwards, the head is large
and globular, the neck elongated and narrow.

In the Gorilla, the femur is much shorter and broader ;
the head is smaller and less globular, the neck is shorter and
set on the shaft more at a right angle. In the Chimpanzee
the femur more resembles that of Man. In the Lemurs it
is very slender and straight, the head is globular, a.nd the
neck very short.

The tibia and fibula are distinct, and well developed in
all the Primates, and are united with each other only at
their extremities. Fabellae are wanting in the highest forms,
but generally present in the others. The patella is usually
broad and flat, and more or less lozenge-shaped.

In the terrestrial CARXIVORA, the femur is straight, mode-
rately slender, and with rather a small head. The fibula is
slender, and in the Dogs curved towards the tibia, the lower
half being closely applied to that bone ; but in the Bears,
and many others, there is a considerable interval between
the bones throughout, except at their articular extremities.
Fabellaj are generally present.

In the Seals, the femur is exceedingly short, broad, and
flattened, with a globular head and an extremely short neck-
The fibula is almost as large as the tibia, especially at the
distal end. These bones are commonly ankylosed together
at their proximal extremities.

332 THE THIGH AND LEG. [CHAI-.

Among the INSECTIVORA, the Hedgehog has a. strong
ridge distally from the great trochanter of the femur, and
several other forms have a similar rudiment of a third
trochanter. As a general rule the fibula is slender, and in
its distal half ankylosed with the tibia, but it is complete
and distinct in the genera Galeopithecus, Tupaia, Centetes,
Ericulus and Solcnodon.

In the CHIROPTEKA, the femur is slender and straight,
with trochanters of nearly equal size, and with a small
globular head, set on a very short neck, with its axis
pointing almost directly to the anterior or dorsal surfaces of
the bone. The fibula varies in condition ; in the Molossiiitf
alone it is well developed. In all other species it is either
very slender or ligamentous in its proximal third (Pteropns)^
reduced to a small bony process above the heel, as in
Megaderma, or altogether absent, as in AJycteris (Dobson).

In the RODENTIA the femur varies much. In the Hares
and Squirrels it is long and slender, with a third trochanter
immediately below the great trochanter. In the Beaver it is
broad and flat, and has a strong ridge about the middle of
the outer side of the shaft. In many other forms (e.g.
Hystrix) neither of these accessory prominences exist, but
the great trochanter is usually much developed.

In Myopotamus and still more in Capromys there is a
strong ridge on the inner side of the middle of the shaft,
indicating the point of insertion of the adductor muscles.

In some forms, as the Beaver, the fibula is distinct,
strongly developed, and separated from the tibia, except at
the extremities, by a wide inter-osseous space. In others, as
the Hares, it is slender, and in its distal half united with the
tibia. The patella is generally elongated, fabellie are usually
developed, and there are often wedge-shaped ossifications in
the semilunar cartilages of the knee-joint.

xvin.] UNCULATA. 333

In the UNC.ULATA, the femur is rather compressed, espe-
cially at the lower end. There is no distinct constriction
of the neck, separating the head from the rest of the bone.
The great trochanter is very large, and usually rises above
the level of the head. The small trochanter is not very
salient, and sometimes, as in the Rhinoceros (Fig. 118), is a

Kir. i:2 - Antcri. r n<r«c« of ™Kht '""ur of Rhinoceros (Rkinoeeroi unicorttfs), J.
h head ; / great irochanter ; f third trochanler.

mere rough ridge. The inner edge of the anterior part of
the inferior articular surface is very prominent. In all the
Perissodactyles there is a strongly marked third trochanter
(0, in the form of a compressed ridge curving forwards.
This is entirely absent in all the known Artiodactyles.

The fibula is subject to great variations among the different
members of the order. In the Rhinoceros, Tapir, Pig, and

334 THE THIGH AND LEG. [CHAP.

Hippopotamus it is complete and distinct, though slender
in proportion to the tibia. In the horse a mere styliform
rudiment of the proximal end is present.

In all Pecora and Tylopoda, a small distinct bone, having
a very definite form, articulating with the lower end of the
tibia, and forming the external malleolus, appears to
represent the distal extremity of the fibula (see Fig. 119).
There is occasionally in addition a slender styliform rudi-
ment of the proximal extremity, but the two are never united
together by bone.

FIG. 119. — Anterior aspect of lower end of the right tibia and fibula of Red Deer
(Corns claphus), \. t tibia ; f fibula.

In the Tragnlina the fibula is long and slender, and com-
plete, but its lower end is indistinguishably blended with
the tibia.

The patella is well ossified, and usually somewhat trian-
gular, with the broad end upwards ; but fabellrc are not
commonly developed in the Ungulata.

In the Hyrax there is a slight ridge on the femur in the
place of a third trochanter. The fibula is complete, and
thickest at its proximal end, where it generally ankyloses
with the tibia. The styloid process of the tibia articulates by
two facets with two corresponding surfaces of the astragalus.

xvin.] CETACEA. 335

The femur of the Elephant is long and very straight ; the
axis of the head is more in a line with that of the shaft than
usual. The great trochanter is not much developed, and
the small trochanter is nearly obsolete. The fibula is com-
plete, distinct, and slender, though considerably enlarged at
the lower end.

In the CETACEA, certain small nodular bones or cartilages
attached by fibrous tissue to the outer side of the pelvic
bone in some of the Whalebone Whales, are commonly

Fir;. 120 — Side view of bones of posterior extremity of Greenland Fight Whale
(Raltrna tnyititctus), J, from Eschricht and Keinhardt. / ischium ; f femur ;
/ accessory ossicle representing the tibia.

regarded as rudimentary and functionless representatives
of the skeleton of the hind limb. In the Greenland Whale
(Fig. 120), there is a proximal, somewhat pear-shaped bone
(/), about eight inches in length, and a smaller conical distal
bone (/), which may represent the femur and tibia
respectively, as suggested by their discoverer, Professor
Reinhardt.1 In Megaptera longimana there is but one such

1 See " Recent Memoirs on the Cetacea," Ray Society, 1866, p. 134.
The bones, articulations, and muscles of the rudimentary hind limb of
the Greenland Whale have been fully described by Professor Struthers,
" Journ. of Anat. and Physiology," vol. xv., i8ii.

336 THE THIGH AND LEG. [CHAP.

bone, and in an adult Fin Whale (Bal&noptera musculus],
sixty-seven feet long, this was found to be only repre-
sented by an oval nodule of cartilage about the size of a
walnut.1 Even this is wanting in some species of the group,
as B. rostra ta and B. boreal is.

No trace of any structure representing the skeleton of
the hind limb, beyond the pelvis, has yet been detected in
any of the Odontocetes.

In none of the existing SIREXIA are there any rudiments
of the hind limb proper, but the extinct Ifalit/uniim had an
ossified femur, articulated to a well-defined acetabulum in
the pelvis.

In the terrestrial and fossorial EDENTATA the femur is
generally short and broad. There is a third trodianter in
the Armadillos and Orycteropus, and a sharp ridge along
the whole external border in Myrmecophaga. The fibula is
as long as the tibia. In the Armadillos these bones are
commonly ankylosed together at each extremity, but curve
away from each other at the middle, leaving a wide inter-
osseous space. In the Anteaters they are both nearly
straight and parallel.

In the Sloths the femur is long, slender, ard flattened
from before backwards. There is no third trochanter ; the
head is large and globular, and placed near the middle of
the proximal end of the shaft, with the axis of which it
more nearly coincides than in most Mammals. The tibia
and fibula are complete, and more nearly equal in si/.e than
in most Mammals. They are both curved, so as to be
separated considerably in the middle part of the leg. The
lower end of the fibula has a conical prominence which
turns inwards, and fits into a depression on the outer side

1 " Proceedings of the Zoological Society, 1865," p. 704.

XVIII.]

MARSUPIALIA.

337

of the articular surface of the astragalus, as a pivot into
a socket.

In none of the MARSUPIALIA is a third trochanter pre-
sent on the femur. The fibula is always well developed,
and its proximal extremity is often produced into a well-
marked process, to the top of which a sesamoid bone is not

Fin. ui.— Anterior aspec* of loncs of right leg of Ornithorh^nckut nnatinut, * .
/femur ; / tibia ; /' fibula ; / patella.

unfrcquently attached ; but, on the other hand, the patella,
except in the Pframelidie, is unossified or quite rudimentary.
In Chatrofus and Ifyf>sif>rymnus the distal end of the fibula
is united with the tibia. In the climbing Australian
Phalangers and Koalas, which have broad hind feet, with an
opposable hallux, there is a greater freedom of movement
between the fibula and tibia than in other Mammals,

333 THE THIGH AND LEG. [CH. XVIM.

approaching in some degree to the rotation often permitted
between the radius and ulna.

In the MONOTREMATA the femur (Fig. 1 2 1,/) is of very
remarkable form, being short, flattened from before back-
wards, narrow in the middle of the shaft, and very broad
at each end ; the trochanters are both well developed, and
the head placed between them on a very short neck, and
with its axis directed quite towards the anterior or dorsal
aspect of the bone. The fibula (_/') is large and straight :
it has a broad flattened process, completed by an epiphysis,
projecting from the upper extremity above the point of articu-
lation with the tibia, much resembling the olecranon of the
fore limb. The tibia (/) is strongly curved in Ornithorhynchus.
but straight in Echidna . In both genera the patella (/) is
well developed.

CHAPTER XIX.

THE HIND FOOT OR PHS.

THE terminal segment of the hind limb is the foot or pes.
Its skeleton presents in many particulars a close re-
semblance to that of the manus, being divisible into three
parts : (i) a gro'ip of short, more or less rounded or square-
shaped bones, constituting the tarsus ; (2) a series of
long bones placed side by side, forming the metatarsus ;
and (3) the phalanges of the digits or toes (see Fig.
122, p. 341).

The metatarsal bones never exceed five in number, and
the phalanges follow the same numerical rule as in the
manus, never exceeding three in each digit. Moreover, the
first digit (counting from the tibial side), or hallitx, resem-
bles the pullex of the hand in always having one segment
less than the other digits. If one toe only is absent, it is
the first or hallux. Unlike those of the manus, any of the
five toes of the foot may be absent or at least rudimentary ;
the fourth and fifth are best developed in Macropus, the
third and fourth in J'fcora, the fourth alone in Choeropus, and
the third alone in Eqniis.

The bones of the tarsus in many of the lower Vertebrata
closely resemble both in number and arrangement those of

z 2

34°

THE HIND FOOT OK PES.

[CHAP.

the carpus, as shown in Fig. 90, p. 281. They have been
described in their most generalised condition by Gegenbaur
under the names expressed in the first column of the
following table.1 The names in the second column are
those by which they are most generally known in this
country, and which will be used in the present work, while
in the third column some synonyms, occasionally employed,
are added.2

Tibiale \
Intermedium i

Astralagus

Talus.

Fibulare

Calcaneum

- Os cahis.

Centrale
Tar* ale I
Tar sal,' 2

Navicular
Internal Cuneiform
Middle Cuneiform

Scaphoideum.
- Entocuneiforme.
- Mi'socunei forme.

Tar sale 3
TarsaL' 4 )
Tar sal,' 5 i

External Cuneiform
Cuboid.

- Ectocumi/ormc.

The bones of the tarsus of Mammals present fewer diver-
sities of number and arrangement than those of the carpus.

1 " Untersuchungen zur vergleichenden Anatomic ; Carpus und
Tarsus/' 1864.

- Recent researches of Baur, "On the Morphology of the Tarsus in
the Mammals/' American Naturalist, January, 1885, make it probable
that a certain bone on the tibial side of the tarsus of Ilyrax, many
Edentates, Ornithorhynchus and Rodents (cf. p. 349) and hitherto
looked upon as a sesamoid bone — is the rudimentary tarsale tibiale,
whilst the astragalus is the intermedium, representing the lunare of the
hand. This tibiale is frequently fused with the centrale, the navicular
bone in such cases containing the elements of the centrale and tibiale.

The homologies of the proximal row of the Mammalian tarsus would
therefore, according to Baur, be the following- -

Fibulare — Calcaneum.
Centrale Navicular.

JWitilt — Sesamoid.

Intermedium — Astragalus.

See also H.irdelebcn, " Zur Morphogie des Hand- und Fuss-skelets. "
Sitzungsbcrichte lena. Gesellsch. Med. Nat. 1885.

XIX.]

GENERAL CHARACTERS.

The proximal row (see Fig. 122) always consists of two
bones, the astragalus (a), which according to Gegenbaur's
view represents the coalesced scaphoid and lunar of the
hand, and the calcaneum (r). The former is placed more
to the dorsal side of the foot than the latter, and almost
exclusively furnishes the tarsal part of the tibio-tarsal or

Kic ill.— Bones of a right human foot, show.ng the epiphyses. i- T tarsus; M
metatarsus ; /'A phalanges : c calcaneum ; a astralagus ; c b cuboid ; « naytcular ;
t ' internal cuneiform : fa middle cuneiform ; c* external cuneiform ; the digits are
indicated by Roman numerals, counting from the tibial to the fibular side.

ankle-joint. It has a rounded anterior or distal projection
called the " head." The calcaneum, placed more to the
ventral or " plantar " side of the foot, is elongated back-
wards to form a more or less prominent tuberosity, the tuber
is, to which the tendon of the great extensor muscles of

342 THE HIND FOOT OR PES. [ciiAr.

the foot is attached. The naricular bone (/»/) is interposed
between the proximal and distal row on the inner, or tibial,
side of the foot, but on the outer side the bones of the two
rows come into contact. The distal row, when complete,
consists of four bones, which, beginning on the inner side,
are the three cuneiform bones, internal (^•1), middle (r2), and
external (^), articulated to the distal surface of the navicular,
and the cuboid (cl>] articulated with the calcaneum. Of these
the middle cuneiform is usually the smallest in animals in
which all five digits are developed; but when the hallux is
wanting, the internal cuneiform may be rudimentary or
altogether absent.

The three cuneiform bones support the first, second, and
third metatarsals respectively, the cuboid supports the fourth
and fifth ; they thus exactly correspond with the four bones
of the distal row of the carpus.

In addition to these constant tarsal bones, there may
be supplemental or sesamoid bones; one situated near the
middle of the tibial side of the tarsus, largely developed in
many Carnivora and Rodents;1 another, less frequent, on the
iibular side ; and a third often developed in the tendons
of the plantar surface of the tarsus, especially large in the
Armadillos. There is also usually a pair of sesamoid
bones opposite each metatarso-phalangeal articulation, on
its plantar aspect.

The development of the bones of the foot corresponds in
the main with that of the bones of the manus. Each tarsal
bone is ossified from a single centre, but the calcaneum has
in addition an epiphysis for the most projecting part or
tuberosity. The four outer metatarsals have each one
centre from which the shaft and proximal end are ossified,
and a large epiphysis at the distal end ; the first meta-
1 See footnote on p. 340.

PRIMATES. 313

tarsal (if it should be so called) and all the phalanges have
an epiphysis only at the proximal extremity. This rule is
almost universal, the most notable exception being found
in the Seals, in which animals (see Fig. 124, p. 347) each
of the metatarsals and all the bones of the toes, except
the terminal phalanges, have epiphyses at both ends of
the shaft.

Order PRIMATES. — In Man (see Fig. 122, p. 341) the foot
is broad, and in the ordinary standing position the whole
length of the plantar surface (at least its outer edge) rests
on the ground, the main axis of the foot being at a right
angle with that of the leg. The inner or tibial side of the
foot is arched before backwards, each extremity only resting
on the ground.

The tarsus is longer than the metatarsus, and the latter
is longer than the digits, but the forms and relations of the
tarsal bones are quite characteristic of the general Mam-
malian type, and the five digits are present with the complete
number of phalanges. The hallux is much stouter than any
of the others, sometimes longer and sometimes shorter than
the second toe. Its metatarsal is articulated to a nearly flat
surface on the internal cuneiform, directed distally, so that
it is placed in the same plane as the other toes, and cannot
be freely separated from, or opposed to, them. There are
no supplementary tarsal bones, and sesamoids are deve-
loped under the metatarso-phalangeal joint of the hallux
only. The phalanges are much smaller, shorter, and more
compressed than are those of the manus. The ungual
phalanges are very small, depressed, and somewhat spatulate.

The principal distinction of the foot of the Simiina from
that of Man is that it is more or less modified into a grasping
organ. The tarsal and metatarsal bones and phalanges are

344 THE HIND FOOT OR PES. [CHAP.

the same in number and relative position, but the articular
surface of the internal cuneiform for the hallux is saddle
shaped, and is directed obliquely towards the inner or
tibial side of the foot. The consequence is that the hallux
is not only somewhat separated from the other digits, but
is also set in a different plane, so that when it is flexed it
turns towards the sole of the foot, and becomes opposed to
the others, much as the thumb does in the human hand.
It is this peculiarity of the pes which has given rise to the
term quadrumanous,Qi "four-handed," occasionally applied
to this group of animals.

The hallux is usually relatively shorter than it is in Man.
In the Orang (Simla satynts] it is particularly short, and
often wants the terminal phalanx, while the metatarsals and
the phalanges of the other digits are long and curved, the
proportions of the three segments of the foot being exactly
the reverse of those of Man, as the tarsal segment is
shortest, and the phalangeal the longest.

The form of the articular surface of the astragalus, and
especially the free mobility of the navicular and cuboid
bones on the astragalus and calcaneum, cause the foot of
the Orang to be set very obliquely on the leg, so that when
placed on a level surface the fibular border only rests on the
ground, and the sole is directed inwards. This position suits
well for grasping vertically-placed boughs of trees, but is ill
adapted for standing or walking on the ground. A similar
disposition is seen in a varying degree in most of the
Monkeys, but in none so markedly as the Orang, in which
animal all the peculiarities by which the simian is distin-
guished from the human foot are most strikingly displayed.

There are usually two sesamoid bones below each
metatarso-phalangeal joint, and a single one below the
cuboid in the tendon of the peroneus longus muscle.

XIX.]

PRIM A TES.

345

The structure of the foot of the Lemunna resembles
generally that of the Simiina, and is in fact one of the
principal bonds of union between these groups. The hallux
is large and opposable, with a flattened ungual phalanx.

The second digit in Lemur has a narrow, pointed, ungual
phalanx, while that of the other digits is flat and spatulate
as in the Sinriina. In Chiromys all the ungual phalanges,

/!

Kl .. 173.— Right pe< of Tarsias spectrum (tint. size), a astragalus; e calcaneum ,
x navicul.tr : f ' internal cuneiform ; S* middle cuneiform ; C* external cuneiform ;
i A cuboid ; I to V the digits.

except that of the hallux, are compressed, curved, and
pointed.

In Perodicticus there is a supplemental ossicle in the
transverse ligament of the plantar surface of the tarsus,
corresponding to that met with in the carpus (see p. 286).

A remarkable elongation of the tarsal segment of the pes

3 fi THE HIND FOOT OR FES. [CIIAV.

occurs in the Galagos and certain other Lemurs, owing to
the modification of two bones, the calcaneum and the navi-
cular; the distal portion of the former, and the whole of
the latter, having the form of nearly cylindrical rods placed
side by side, while the other bones retain nearly their normal
form and proportions. A precisely similar modification is
carried to a still greater extent in the genus Tarsii/s (see
Fig. 123, p. 345).

All the terrestrial GARNI VORA have the normal number of
tarsal bones, with very little deviation from their normal
form and relations.

The hallux is present and well developed, though shorter
than the other toes, in the Ursidic, Procyonida, Mustelidie,
and most of the Virerridcc. In the Canidcc, Hyanidtf, and
Felidic, it is only represented by a rudimentary metatarsal.
The other four metatarsals and digits are always well de-
veloped and subequal. The ungual phalanges in the Felida:
present the same characters as those of the fore limb (see
p. 288).

In the Bears, the foot is flat, broad, and plantigrade. In
the Dogs and Cats, it is longer and narrower, and the heel
is raised from the ground in walking.

In the Sea Otter (Enhydra), the hind foot approximates
to that of the Seals. It is very large and flattened, almost
fin-like, and much everted ; but the hallux is still shorter
than any of the other digits, and the two outer toes are the
longest.

In the Seals the pes is completely modified for a special
purpose. It has no longer any function as an organ of
support or progression on land, and is habitually directed
backwards, with the dorsal surface outwards, and the
plantar surface in contact with the corresponding part of
the opposite limb. The calcaneum is very short, its tube-

XIX.

CARNIVORA.

347

rosily being almost obsolete. The two lateral digits (first
and fifth) are both longer and much stouter than the others ;
the middle digit is the shortest. In the Elephant Seal
( Macrorhinus leoninus\ all the phalanges (except the
terminal ones) have epiphyses at both ends of the shaft
(see Fig. 124).

FIG. I2» — Porsal Mirfa.6 of rij{ht pes of young Elephant Seal (Mactorhinus
ttoniniit), \, showing the epiphyses. The letters as before.

In the Otariidic, or Eared Seals, and the Walrus, which
use the hind feet in walking, these modifications from the
ordinary type are not so marked, the calcaneum having a
greater backward projection, and all the digits being of
nearly equal length. In both there is a large sesamoid on
the tibial side of the tarsus.

In the greater number of the animals of the order

34-S THE HIND FOOT OR PES. [CHAP.

INSECTIVORA the tarsus is quite normal, and there are five
digits, all with curved, pointed, moderately developed
ungual phalanges, the hallux being the shortest. In the
Mole, the pes is narrow, having none of the modifications
of structure observed in the manus, except that there is
an unusually large slender sesamoid on the tibial side of
the tarsus, corresponding to the falciform bone of the fore
limb. In the Water Moles (Myogale), the pes is remark-
ably large and almost fin-like.

In the African genera Petrodromus and Rhyncfwcyon, the
hallux is only represented by a rudimentary metatarsal.
The last-named animal has a remarkably elongated pes,
produced partly by the length of the metatarsals, and partly
by a peculiar elongation of all the bones of the distal
row of the tarsus, the cuboid and three cuneiform bones.
Contrary to what occurs in the Galagos, the navicular and
calcaneum are of normal proportions.

Order CHIROPTKRA. — The tarsus is very short ; the tuber
calcanei is a slender curved process sometimes of con-
siderable length, supporting the interfemoral membrane ;
the metatarsals are equal and rather short ; the phalanges
elongated and subequal in length, the hallux being rather
the shortest ; the ungual phalanges are long, curved, com-
pressed and pointed. In the Leaf-nosed Bats (PhyllorhinintR)
and the anomalous genera, Thyroptcra and Myxopoda all
the toes have only two phalanges.

Order RODKNTIA. — The structure of the pes varies much
in different members of this order. In the Beaver, as in
most swimming quadrupeds, it is disproportionately large
and fiat. The five digits are well developed, but the third
and fourth are considerably longjr and stouter than the
others. The base of the fifth metatarsal is articulated to
the outer side of the fourth metatarsal, and not directly to

XIX.]

KODENTIA.

349

rb

the cuboid. The middle cuneiform is very small. There is
a large sesamoid bone on the tibial side of the tarsus,
articulating with the astragalus, navicular, and internal
cuneiform.1 The tuberosity of the calcaneum is long and
obliquely compressed.

The functional digits in other Rodents may be five, as
in the Rats, Porcupines, and Squirrels ;
or the hallux may be suppressed, as in
the Hares ; and occasionally the fifth
digit is also wanting, reducing the
number to three, as in the Capybara,
Viscacha, and Agouti. The last-named
animal has the three metatarsals elon-
gated and closely pressed together,
and all the digits with short subequal
phalanges. A still further modification
of the same type leads to the singular
condition of pes met with in the
Jerboas (genus Dipus, see Fig. 125),
which at first sight resembles that of
a bird. The three metatarsals are
ankylosed together to form a single
bone, which supports the three separate
short digits, each with three phalanges.
These alone are applied to the ground,
the tarsus and long metatarsal segment
being raised almost vertically. The hallux is wanting or
rudimentary, but in some species (Alactaga) there is a small
fifth digit.

All the animals of the order UNGULATA are digitigrade,

1 In Cercolabts and Erelhizon there is also developed a claw-like bone,
articulating with the " sesamoid."— G. 13aur, " American Naturalist,"
1885.

FIG. 125.— liones of righ:
pes of Jerboa (Dipvs
agyptius), \.

350 THE HIND FOOT OA' PES. [CHA-.

the heel being raised from the ground, and the metatarsal
segment usually much elongated. There is no trace of a
hallux in any existing species. As in the corresponding
segment of the fore limb, the pes is formed upon one or
other of two distinct types, each characteristic of one of the
sub-orders.

In the Perissodactyla, the third digit is the largest, in tin-
centre of the foot, and symmetrical in itself; the second and
fourth are smaller, and nearly equal in length, though some-
times quite rudimentary. A line drawn through the centre
of the foot passes through the axis of the third digit, and
the middle of the external cuneiform, navicular, and as-
tragalus. The distal surface of the astragalus has a large
articular surface for the navicular, and a very small one for
the cuboid, which bone is of comparatively less importance
than in the Artiodactyla. The calcaneum does not articu-
late with the lower end of the fibula.

The Rhinoceros (Fig. 126) and Tapir have all the usual
bones of the tarsus well developed. The internal cuneiform
has a curved process projecting backwards. The middle
cuneiform (c2) is very small. The whole foot is compara-
tively short and broad. The second and fourth toes
are well developed, being nearly as long as the middle toe.
The phalanges resemble those of the fore limb. In the
Tapir the pes differs from the manus in wanting the fifth
digit.

In the Horse (Fig. 127), the middle toe is greatly
enlarged, and the second and fourth reduced to slender
styliform metatarsals, about three-fourths the length of the
second, but supporting no phalanges. The navicular (//)
and the external cuneiform (c*) are very broad and flui.
The cuboid (cl>) is small, and the internal and middle
cuneiform bones are small and united together.

XIX. ]

UNGUI.ATA.

3.5'

Various gradational stages between the complete tridac-
tyle foot of the Rhinoceros and the monodactyle foot of
the Horse are met with in extinct species of the Perisso-
dactyla.

In the Artiodactyla the third and fourth digits are nearly
equally developed, and their ungual phalanges are flattened
on their contiguous sides, so that together they constitute a

Kl<;. 116.- Dorsal surface of right lar«u
of khinocero> (A'A/rtiHvnM Sumatra/

FH;. 127. — Dorsal surface of right tarstifc
of Horse (Equus cakaJliiS), \.

symmetrical form. The second and fifth toes, when present
are also equal, but smaller than the others. A line drawn
through the centre of the foot has on its tibial side the third
digit and metatarsal, the external cuneiform, the navicular
and half the astragalus ; and on its fibular side the fourth
digit and metatarsal, the cuboid and the other half of the

THE HIND FOOT OR PES.

[CHAP.

astragalus. The distal articular surface of the astragalus is
divided into two nearly equal facets, one for the navicular
and one for the cuboid. The calcaneum has an articular
facet for the lower end of the fibula.

In the Suina (Fig. 128) all the tarsal bones are distinct.
The four toes are well developed, and the metatarsals are

FIG. 1 23. — Dorsal surface of right tarsus
of Pig (Sus sere/a)^ J.

Fir.. 129. — Dorsal surface of right tarsu
of Red Deer (Cen-us tlaphiis), J.

usually distinct. The foot is relatively shortest and broadest
in the Hippopotamus, the outer toes being nearly as long as
the others, and the lingual phalanges very short, broad,
and rounded in front. The Peccaries show a transition
towards the ruminating sections of the order in the reduc-
tion of the size of the outer toes and the confluence of the

xix.] UNGULATA. 353

third and fourth metatarsals. On the hind foot the filth
digit is absent though the second is tolerably well developed.

In the Tylopoda the cuboid and navicular are distinct.
There is rio internal cuneiform. The second and fifth digits
are entirely absent. The metatarsals of the third and fourth
are united except at their lower extremity. The phalanges
resemble those of the fore foot.

In the Tragulina the cuboid, navicular, and two outer
cuneiforms are united to form a single bone. The third and
fourth metatarsals are confluent. The second and fifth are
complete, extending between the small digits and the tarsus,
but are very slender.

In all the Ptcora (Fig. 129) the cuboid (cb} and navicular
(//) are united, as are the second and third cuneiform bones,
and in some Deer (Ctn'ulus and Pudu) these latter are
further united with the cubo-navicular. The first cuneiform
is always distinct, though small.1 The third and fourth
metatarsals (m in. and /// iv.) are united in the same manner
as the mctacarpals, and the phalanges of the digits are very
similar to those of the manus. The second and fifth
metatarsals are always wanting, and bones of the corre-
sponding digits are absent in the Giraffe and most of the
Oxen, Sheep, and Antelopes. In the Deer there are
usually three small phalanges to each of these digits, not
directly articulated with the rest of the skeleton. A large
oval sesamoid is commonly present in the plantar surface of
the tarsus.

The pes of the Hyrax closely resembles that of the
Rhinoceros, but the ungual phalanx of the second digit is
cleft almost to its base. The fifth metatarsal is represented
by a small nodule ; the astragalus articulates with the cuboid.

1 See Sir Victor Brooke, " Troceedings of the Zoological Society,
1874," p. 34.

A A

354 THE HIND FOOT OR PES. [CHAP.

In the PROBOSCIDEA the pes is short and broad, but
smaller and more compressed than the manus, and in the
more rudimentary condition of the two lateral digits shows
a greater tendency to approach the Perissodactyle form.
The astragalus is very flat, and has no articulation with the
cuboid. The internal cuneiform is produced distally, as is
the corresponding bone of the manus.

Order ED KN TAT A. — In the Sloths the pes much resembles
the manus in its general characters, being long, very narrow,
and curved, terminating in strong, compressed, pointed
ungual phalanges, supporting hook-like claws. The tarsus
is short ; the astragalus has a deep, cup-shaped cavity on its
outer side, into which a conical projection of the lower end
of the fibula is received.

The appellation " Two-toed " applied to the genus Cho-
Lrpus refers only to the anterior limb, for in the pes the
three middle toes are functionally developed, and of nearly
equal sixe in both the genera of the family.

In Bradypus the tuber calcanei is long, compressed, and
widened at the extremity. The tarsal bones have a great
tendency to ankylosis. The first and fifth metatarsals are
very rudimentary, and support no phalanges. The proxi-
mal phalanges of the three middle digits are very short, and
coalesce very early with the metatarsals, as in the corre-
sponding part of the upper extremity.

In Cholcepus, the tuberosity of the calcaneum is very
small. The tarsal bones remain distinct from one another.
The proximal phalanges of the three middle digits are
extremely short, but not ankylosed with the metatarsals.
The first and fifth metatarsals are about three-fourths of the
length of the others, flattened, and gradually diminishing in
size to their free ends.

In nearly all the members of the Entomophagous section

MX.] EDENTATA. 355

of the Edentata the pes is much more normal in type, and
adapted for plantigrade progression on the ground. It does
not even present any modifications corresponding to those
observed in the manus of the same animals. The normal
number of tarsal bones, and the complete number of pha-
langes, are always present in each digit. Of these the second
and third are usually the longest, the fourth next, and the
first and fifth shortest.

The little prehensile-tailed Tree Anteater (Cycloturus
didactylus) has the pes modified into a climbing organ.
The hallux is rudimentary, consisting of a metatarsal and
one phalanx, concealed beneath the skin, but the four other
toes are subequal and much curved, with long, pointed,
compressed, ungunl phalanges. The tuber calcanei is di-
rected towards the plantar surface, and parallel with it, and
extending to about double its length is the greatly elongated
sesamoid ossicle of the tibial side of the foot. These
together support the prominent calcarine cushion to which
the nails are opposed in climbing.

In the MARSUPIALIA, the hind foot is subject to great
modifications, some of the genera presenting very striking
deviations from the typical condition.

The seven bones usually found in the Mammalian tarsus
are always present and distinct from each other, but the
astragalus is relatively smaller and more flattened than in
placental Mammals. In the climbing Marsupials espe-
cially, the articular surface for the fibula, instead of being
perpendicular to that for the lower end of the tibia, is almost
in the same plane with it ; and in all, the " head," or portion
of the astragalus which projects forwards to articulate with
the navicular, is very slightly developed

In the American Opossums (Didelphidcz), the foot is short
and broad ; the hallux is stout, placed at right angles with,

A A 2

356 THE HIND FOOT OR PES. [CHAP.

and opposable to, the other four digits ; it has a short
rounded terminal phalanx, which bears no nail. The other
digits are subequal, and have compressed, pointed, curved
ungual phalanges.

In the Dasyuridcz, the foot is comparatively narrow ; the
second,. third, fourth, and fifth toes are subequal; the hallux
is either very small and placed close to the others, or com-
pletely suppressed, as in the Thylacine.

In the Wombats (Phascolornyida), the foot is short and
broad ; the hallux is very short, with only one rounded
phalanx, and divaricated from the other toes. These are
nearly equal in length ; the fourth and fifth are stouter than
the second and third, thus showing a slight tendency towards
the condition met with in the next group.

In all the remaining Marsupials a peculiar condition of
the pes, called syndactylism, prevails. Whatever the con-
dition of the other toes, or whatever the general form of
function of the foot may be, the second and third metar-
tarsals and digits are very slender, and inclosed nearly to
their extremities in a common integument, so that they look
externally like one small toe with two claws.

In the Kangaroo (Macropiis) the whole foot (Fig. 130) is
very long and narrow, and rests entirely on the ground in
the ordinary position of the animal. The tarsal segment is
short, the metatarsus very long. The cuboid is greatly
developed, the navicular and the three cuneiform bones
exceedingly small, in conformity with the condition of the
digits they respectively support. There is a sesamoid on
the plantar surface of the tarsus. The fourth metatarsal
and digit are enormously developed, the fifth moderately
so ; the second and third are nearly as long as the fifth, but
excessively attenuated. There is no rudiment of a hallux.
The ungual phalanges are conical, pointed, slightly curved

xix.] MARSUPIALIA. 357

above, and flattened on the under surface. The whole foot
is much compressed laterally, especially at its hinder part,
so that the proximal ends of the second and third are thrown
behind that of the great fourth metatarsal, and entirely
concealed in a view of the dorsal surface of the foot.

The Tree-Kangaroos of New Guinea (Dcndro/agJts),
which habitually live among the boughs of large trees, have

KH-. i-.o. -P.one* of right pe< of K.ati- Fir.. 131. — Hones of right foot of Pha-
it-"'"0 {Macnifut tuniH-ttiJi, J. lanjjer (PkalaHgista rulftina), •[.

the feet constructed on the same type, but shorter, and more
laterally extended. Hypsiprymnadon moschatus, a species
of Rat Kangaroo, lately discovered by Ramsay in North-
east Australia, differs from all other members of the family
ida in the possession of a small prehensile hallux>

7///: H!.\'D I-OOT OK

[CHAP.

without a nail, and presents therefore an approximation to

the next group.

In the leaf eating, climbing Australian Opossums (Phalan-

%:sta, Fig. 131; and Koalas < Phaxolarctos) the second and

ihird toes are al-o very slender, but the fourth and fifth are
more equal, especially in length, the
foot is broad, and there is a strongly-
d.-veloped prehensile and opposable,
through nailless, haliu.x.

The insect- and root eating, ground-
dwelling Bandicoots (Piramelid*} dif-
fering in many other respects from the
Kangaroos, have their hind foot con-
structed on txact'.y the same type as in
Macrifus. even to the relative length
of the different dibits, though there is
often a rudiment of the metatarsal of
tiie hallux. In one remarkable genus
i Ciurrcfus), already mentioned on
account of the peculiar structure of the
man us (see Fig. 1 1:. p. 310), the same
type is carried to a great extreme, the
fourth toe (>ee Fig. 137) remaining of
a prodigious size, and the fifth being
reduced to even smaller dimensions
than the second or third.
MOXOTREMATA. — In both species the seven usual bones

of the tarsus are complete and distinct,1 and the five digits

have the normal number of phalanges.

1 It has been stated that the culv 1 1 in the Ornithorhynchus is divided
into two b >nes, a-< i:i some reptiles, one supporting the fourth and the
other the fifth metatarsal ; but this U not the cose in any specimen
which I have examined.

if,. 132. — Fonc< • f

foot of Cf!<rr:'flti ..

naiis (iiat. >uc).

xix.] MONOTREMATA. 359

In the Ornithorhynchus the proximal articular surface of
the astragalus is divided by a deep groove into two distinct
heads, one for the tibia, and the other for the ftbula, the
latter being the larger of the two ; the inner side has a cup-
shaped socket, into which fits an incurved conical process
from the lower end of the tibia. The tuberosity of the cal-
caneum is broad and bifid at the extremity, and directed
not backwards, but towards the tibial side of the foot. In
the male there is an additional, large, flat, curved ossicle, on
the hinder and tibial side of the plantar aspect of the tarsus*
articulated chiefly to the tibia, which supports the peculiar
perforated horny spur characteristic of this sex, the function
of which has not yet been discovered. There is also a small,
rounded, supplementary ossicle, below the tibial edge of the
tarsus, near the articulation between the astragalus and
scaphoid. The metatarsals increase in length from the first
to the fifth. The phalanges are all rather long and slender-
The four outer toes are nearly equal ; the hallux is somewhat
shorter. The ungual phalanges are compressed, slightly
curved, and very sharp-pointed.

In the Echidna the astragalus is large, with an irregular^
broad, rounded, proximal articular surface, not divided by
a groove, and with a much less distinct fossa, for the in-
ternal malleolus. The tuber calcanei is directed forwards,
it is also bifid, and its external process is much longer than
the other and curved towards the plantar surface of the
foot. The spur of the male, and the ossicle which supports
it, are much smaller than in the Ornithorhynchus: The
metatarsals are shorter and broader ; they increase in length
from the first to the fifth. The hallux is very short, and has
a flattened, conical, ungual phalanx. The proximal and
middle phalanges are all very short and broad. The ungual
phalanx of the second digit is extremely long and falcate,

360 THE HIND FOOT OR PES. [CH. xix.

the others gradually diminish to the fifth. The ends of the
toes are turned outwards and backwards in the ordinary
position of the animal.

The ungual phalanges of both extremities in the Mono-
tremata have a deep median groove, near the base of the
under surface, leading at its distal extremity into a foramen.

CHAPTER XX.

1 HE CORRESPONDENCE BETWEEN THE BONES OF THE ANTE-
RIOR AND POSTERIOR EXTREMITY AND THE MODIFICA-
TIONS OF THE POSITIONS OF THE LIMBS.

THAT a general correspondence exists in the plan of con-
struction of the anterior and posterior extremity cannot fail
to strike the most superficial observer, though to follow out
this correspondence into all its details has severely exercised
the ingenuity of many an anatomist

It would he quite beside the character of the present
work to give an historical account of the numerous and
very various views which have been held upon this sub-
ject,1 but I propose to lay before the student in a condensed

1 For the bibliography of this question, see Ch. Martins, " Nouvelle
c tinparaison cits uieuibres," (Mem. de 1'Academie de Montpellier,
1^57); Mivart, "On some Points in the Anatomy of Echidna
hystrix," (I. inn. Soc. Trans, xxv. 1866) ; and Rolleston, " On the
Homologies of certain Muscles connected with the Shoulder Joint,"
(ibid. xxvi. 1869). See also Humphry's "Observations in Myology,"
1872; A. Cioette, " Ueber Entwickelung und Regeneration des Glied-
ma-senskclets der Mulche," (Leipzig, 1879) ; H. Strasser, " Entwicke-
lung der Extremitseten-knorpel bei Salamandern und Tritonen," (Mor-
phul. Jahrb. 1879); A. Sabatier, " Com para ison des Ceintures et des

362 THE CORRESPONDENCE BETWEEN THE [CHAP.

form such portions of the general outcome of these researches
as appear to be most satisfactorily established, premising,
however, that all the statements hereinafter to be made
have not yet met with universal assent.1

In the first placj, it is perfectly obvious that the fore and
hind limbs have each a similar division into four main seg-
ments ; the shoulder girdle, the arm, the fore-arm, and the
manus of the one representing respectively the pelvic girdle,
the thigh, the leg, and the pes of the other.

To proceed to further details, it is necessary to place the
limbs (at least in imagination) in an exact corresponding
position — one, in fact, which is often impossible in the adult
animal on account of the modifications of the articular sur-
faces to suit the posture best adapted for the habits and
mode of life of the individual, but which is the position of
the limbs of many Mammals, when they first appear as bud-
like processes from the side of the body of the embryo. In
this position - the limbs are extended at right angles to the

Membres antericurs et posterieurs dans la serie des Vertebres," (Mont-
pcllier, 1880); G. Gegenbaur, " Untersuchungen zur vergleich. Ana-
tomie ; I. Carpus und. Tarsus," (Leipzig, 1864, p. 115 ff. ) ; and "Zur
Gliedmassenfrage," (Morphol. Jahrl>. v. 1879) ; F. M. BalLmr, " A
Treatise on Comparative Embryology," (London, iSSi).

1 For an exposition of the very opposite hypothesis of " Antero-
posterior Symmetry," see Jeffries Wyuian, " On Symmetry and Homo-
logy in Limbs," (1'roc. Boston Nat. Hist., June, 1867, p. 277) ; and
the elaborate series of papers by Dr. Flliott Coues, published in the
" Medical Record " (New York) for 1870.

2 This horizontal position is probably not the primary one, and
wherever it occurs, as in Selachians and many Mammalia, it is a secondary
modification of the original position of the cheiropterygium, in which
the long axis of the limb is directed obliquely outwards and backwards
towards the tail, the ulna and the fifth finger looking dorsally, and the
palmar and plantar surfaces of hand and foot looking towards the sides
of the body. This position was that of the limbs of the Enaliusauri, and is
still repeated by the Cctacea and by Ceratodus and the e-nbryonic limb.t of

xx.] ANTERIOR AND POSTERIOR EXTREMITY. 363

axis of the trunk and parallel to each other, as in Fig. 133,
A and B. There is then to each limb a superior or dorsal
surface (turned towards the observer in the figure), an
inferior or ventral surface, and an anterior and a posterior
edge. These last are called by Professor Huxley pre-axial
and post-axial (in reference to the axis of the limb itself) to
avoid the confusion with anterior and posterior in the modi-
fied positions they assume in Man and various animals. In
the figures the pre-axial side is left light, and the post-axial
side is shaded.

The dorsal surface of the anterior extremity includes the
back of the hand and the extensor surface of the fore-arm
and arm. The dorsal surface of the posterior extremity
includes the dorsum of the foot, front of the leg, and the
extensor surface of the thigh. The pre-axial border of the
anterior extremity has in it the pollex, the radius, the
condyle commonly called " external," and the greater tuber-
osity. The pre-axial border of the posterior extremity in-
cludes the hallux, the tibia, the condyle commonly called
" internal," and the lesser trochanter. All these parts, then,
should be regarded as serially homologous.

Leaving for the present the shoulder and pelvic girdles
out of consideration, we will next consider the adaptive
changes which take place in the segments of the limb
proper in various animals. These will be best understood
by dividing them into stages (all of which are represented
in the diagram), though it is not meant to imply that the
limbs actually go through so many distinct phases in the
course of development, as all the various modifications from
the primitive to the most adaptive positions may take place
gradually and even simultaneously.

the Amphibia, and is in harmony with Gegenbaur's derivation of the
limbs from the archipterygium. (H. G.)

564 7 HE CORRESPONDENCE BETWEEN THE [CHAP.

KiG. 133. — Diagrammatic representation of the positions of the limbs of Mammalia.
'1 lie pre-axial border is left light, the post-axial border is shaded, in all the figures.
Limbs of the right side are represented in all cases. (A) dorsal aspect of the
anterior extremity in its primitive unmodified position ; gl> glenoid border of the
scapula; j- spine ; ch coracoid border; ssf sub-scapular fossa : //post-scapular (in-
fra-spinal)fo:-sa ; c coracoid ; h humerus ; gt greater, radial, or pro-axial tuberosity ;
// lesser, ulnar, or post-axial tuberosity ; cc external (in the modified position),
radial, or pre-axial condyle ; ic internal, ulnar, or post-axial condyle ; r radius ;
H ulna; I polkx ; v fifth digit. (H) dorsal aspect of the posierior extremity in the
same position; nb acctabular border of the ilium; fb pubic border; it> ischial
border ; gs gluteal surface ; is iliac s'irf:tce ; i ischiinn ; yJpubis ; yfemur ; // lesser,
tibial, or pre-axial trochanter ; £•/ greater, fibular, or post-axial trochanter; ic in-
ternal (in the modified position), tibial, or pre-axial condyle : <r external, fibular,
or post-axial condyle ; t tibia ; f fibula ; I hallux ; v (ifih digit, (c) th- anterior
extremity, with the humerus in the same position, bin the elbow- and wrist-joints
bent. (D) the posterior extremity in the same position.

xx.] ANTERIOR AND POSTERIOR EXTREMITY. 365

In what may be considered the first stage of modification
(Figs, c and D), each segment of the limb is simply bent
upon the one above it. The proximal segments (humerus

FIG. 134. — Diagrammatic reprevntation of the positions of the limbs of Mammalia,
continued. (K) the anterior-extremity with the same flexures as in c, but with the
whole limb rotated backwards The pre-axial side is external. The letters as
before, (f) the posterior extremity, with the joints bent, and the whole limb rotated
forward-, as in the ordinary position of quadruped Mammals. The post-axial side
is external (<;) the humerus in the same position as in E, but the fore-arm rotr.ted
as in the ordinary position of quadruped Mammals. Whilst the pre-axial side of
the humerus remains external, the post-axial side of the inanus is now external.
(H) the anterior extremity of a Cetacean (H yperoodon), dorsal surface, (t) the
posterior extremity of a Seal, dorsal surface.

and femur) remain unchanged in position, the dorsal surface
still looking upwards, and the ventral surface downwards ;

366 THE CORRESPONDENCE BETWEEN THE [CHAP.

the middle segment is bent downwards, so that its ventral
surface faces inwards and its dorsal surface outwards ; and
the joints between these segments (elbow and knee) form
prominent angular projections. The third segment being
bent to a greater or less degree, in the opposite direction
to the middle one, retains much of its primitive position,
the dorsal surface being directed upwards and the ends of
the digits pointing outwards. The relations of the pre-axial
and post-axial borders of the limb are unchanged. No
Mammal habitually carries its limbs in this position, although
the climbing Galeopitheats and the Sloths are not far from
it. It is, however, very nearly the normal position of
some Reptiles, especially the Tortoises, though it is ill
adapted for anything but a very slow and clumsy mode of
progression.

The next change, and one which takes place at a very
early period in embryonic life, and which is one of the most
essential in giving the characteristic conformation of the
extremities of the higher Vertebrates, is a rotation of the
whole limb from the proximal end, though in opposite
directions in each case.

The anterior extremity (see Fig. E.) is rotated from the
shoulder, through nearly a quarter of a circle, backwards, so
that the humerus, instead of being at a right angle to the
axis of the trunk, is nearly parallel with it, the elbow points
backwards, the pre-axial side is outwards, and the post-axial
side towards the middle line of the body, and as long as the
radius and ulna retain their primitive parallel position, the
manus is placed with the ends of the digits directed back-
wards, the pre-axial side being external.

The hind limb (see Fig. F.) is, at the same time, rotated
from the hip to the same extent forwards, so that the femur
is also nearly parallel to the axis of the body, but with the

xx.] ANTERIOR AND POSTERIOR EXTREMITY. 367

knee projecting forwards ; the pre-axial side is inwards and
the post-axial side outwards ; the tibia and fibula are parallel,
the former internal and the latter external ; the foot has the
ends of the digits directed forwards, the hallux or pre-axial
digit is on the inner, and the fifth or most post-axial digit
is on the outer, side.

In this position the hind limb remains, subject only to
minor modifications, in nearly all terrestrial Mammals; but
the Walrus, and to a certain extent the Sea-Lions, alone
carry the fore limb as described above without further
modification.

The next stage, affecting the fore limb alone, consists in
the rotation of the lower end of the radius around the ulna
which brings the distal extremity of the manus round from
the back to the front of the limb (see Fig. c.). In most
Mammals the limb is permanently fixed in this position,
and the bones of the fore-arm become greatly modified in
consequence, as described in Chapter XV. It will now be
understood how, though the outer side of the humerus
corresponds with the inner side of the femur, in ordinary
quadruped progression, yet the outer side of the manus
corresponds with the outer and not the inner side of
the pes.

To these general conditions there are certain modifica-
tions met with in some animals, and certain exceptions
in others.

The modifications with regard to the anterior extremity
are that the humerus may be quite horizontal, or its distal
end may incline upwards, or, as is much more frequently the
case, it may incline somewhat downwards, so that the dorsal
surface is posterior and the ventral surface anterior ; the fore-
arm in the ordinary resting position may be quite vertical,
or inclined with its upper end backwards ; the whole of the

368 THE CORRESPONDENCE BETWEEN THE [CHAP.

manus may rest entirely on the ground, as in the so-called
" plantigrade " or rather " palmigrade " animals, or the
proximal part, the tarsus and metatarsus, may be raised and
placed more or less vertically, the limb resting either
on all or only on the terminal phalanges, according
to the completeness of the " digitigrade " mode of
progression.

Similar modifications occur in the hind limb. The
femur is usually inclined with its distal end downwards, so
that the dorsal or " extensor " surface is anterior, and the
ventral or " flexor " surface posterior. In the Elephants it
is very nearly vertical. In most animals which occasionally
assume the upright position, as the Kangaroos and some
Rodents, the femur is ordinarily inclined upwards at its
distal extremity, so that the knee is above the acetabulum,
and the pelvis slung as it were between the two hind limbs.
In Man, on the other hand, in standing or walking the
femur is nearly vertical with the distal ends downwards, and
the pelvis is supported on the top of the limbs.

The positions of the limbs which are quite exceptional
are those of certain aquatic animals.

In the Cetacea (Fig. H.) none of the segments of the
anterior limb undergo any deflection from the primitive
straight condition, nor is there any rotation of the bones of
the fore-arm. The only changes which take place are a partial
rotation backwards from the shoulder, and a slight turning
downwards of the pre-axial border. In the Sirenia and the
Seals, there is a slight bend at the elbow and the wrist,
but little or no rotation of the fore-arm.

In the hind limb of the Seal (Fig. i) there is very little
flexure at the joints, and the whole limb is turned backwards
instead of forwards from the hip, and at the same time
rotated on its axis, so that the pre-axial border becomes

XX.] ANTERIOR AND POSTERIOR EXTREMITY. 369

turned downwards. The skeleton of this limb, therefore,
and that of the fore-limb of the Cetacean, being retained
normally in almost exactly similar positions, are well adapted
for demonstrating the correspondence between the re-
spective bones of which they are composed (see Figs.
H. and i.).

The necessity of the modifications in the direction of the
axes of the heads of the humerus and femur spoken of pre-
viously will easily be understood by a consideration of the
relative positions that these bones are adapted to assume.
Thus the axis of the head of the humerus in the majority of
Mammals is inclined towards the post-axial side of the shaft
of the bone, while that of the femur is inclined towards
its pre-axial side.

Hitherto nothing had been said about the shoulder
and pelvic girdles, because the correspondence of their
parts is not so easily explained, nor so generally recog-
nised, as that of the segments of the limb proper. The
following view appears to be, of those yet suggested, the
most probable.

It has been already shown (Chapters XIV. and XVII.)
that the lateral half of each girdle consists primarily of a
bar or rod placed vertically, and divided into an upper and
a lower segment, the point of attachment of the limb being
close to the junction of these two segments. The upper
segment in the fore-limb is the scapula, in the hind-limb the
ilium ; the lower segment in the fore-limb is the coracoid,
in the hind-limb the ischium and pubis.

In every Mammal both scapula and ilium may be re-
solved into bars or rods of three-sided or prismatic form.
The two extremities of each bar are placed, as regards the
general position of the trunk, dorsally and ventrally. The
dorsal or upper extremity is capped by the supra-scapular

B B

370 THE CORRESPONDENCE BETWEEN THE [CHAP.

epiphysis in the shoulder girdle, and by the corresponding
supra-iliac epiphysis in the pelvic girdle. The ventral
or inferior extremity enters into the formation of the
glenoid or the acetabular articular cavity, as the case
may be, and joins the coracoid or the ischial element ol
he girdle.

The bar, supposed to be in a nearly vertical position, has
three surfaces and three borders. In what may be, at least
theoretically, considered one stage of their primary position,
the surfaces of each bar are — (i) Inner or vertebral, turned
towards the vertebral column ; (2) Pre-axial, corresponding to
the pre-axial line of the limb (Fig. 125, A ff, B is); (3)
Post-axial, corresponding to the post-axial line of the limb (A
ssf, B gs). The borders are — (i) External, in a line with the
middle of the dorsal surface of the limb, and terminating
below at the upper margin of the glenoid or acetabular cavity
(A£/', i? aft) ; (2) Antero-internal, terminating below in the
acromion or in the pubis (A s, H //>) ; (3) Postero-internal,
terminating below in the coracoid, or the ischium, as the
case may be (A cl>, n il>}.

The correspondence between these parts of the scapula
and ilium will be better understood by placing them in
a tabular form, the middle column showing the names
expressed in the generalized or ideal condition applicable
to both in their primitive condition, and the column at each
side giving the special terms applied to each part in its
variously modified forms.

ANTERIOR AND POSTERIOR EXTREMITY. 371
SURFACES.

SCAPULA. IDEAL.

PELVIS.

Pre-scapular fossa. I. Vertebral.
Supra-spinous fossa.

i

Sacral surface.
Inner surface of ilium,
behind linea arcuata
interna, including the
at titular surface for
the sacrum, and the
portion of the bone
above and below this.

Post-scapular fossa. ;. Pre-axial. Iliac surface.
Infra-spinous fossa. , Internal iliac fossa.

Sub-scapular fossa. 3. Post-axial. Gluteal surface.

BORDERS.

SCAPULA.

IDEAL.

Glenoid border.
Posterior border in

most animals.
Axillary border in

Man.

Spir.e.

Coracoid bonier.
Anterior border in

most animals
Superior border in

Mr.n.

I. External.

Acetabular border
Anterior border.

2. Antero-internal. Pubic border.

Linea arcuata interna.

3. Postero-internal. I schial border.

Posterior border.

As the humerus in ordinary quadruped Mammals is
rotated backwards from its primitive position, and the femur

B B 2

372 THE CORRESPONDENCE BETWEEN THE [CHAI-.

is rotated forwards, so that the pre-axial side of the first
becomes external, and the really corresponding side of the
other becomes internal, so it is with the scapula and ilium.
Each has undergone a rotation on its own axis, through
nearly a quarter of a circle, and in the opposite direction
(see Fig. 134, E. and F), so that the inner surface of the one
comes to correspond with the outer surface of the other,
the anterior border of the one with the posterior border of
the other. The long axis of each is also differently inclined,
the upper end of the scapula leaning backwards, while that
of the ilium is inclined forwards, which makes the resem-
blance between them seem still more obscure.

These views are considerably strengthened by a considera-
tion of the disposition of the muscles connected with the
various bones in question.1

The principal differences between the shoulder and pelvic-
girdles of the Mammalia are two: — (i) The rudimentary
condition of the inferior or ventral section of the girdle (the
coracoid) in the former, as compared with the vast deve-
lopment of the corresponding part of the lower extremity :
(2) the free condition of the anterior as compared with the
posterior girdle. It is neither attached to the vertebral
column above, nor does it (except in the Monotremata) join
the opposite part in the middle line below. To compensate
for this, a clavicle is superadded to the anterior girdle in
many Mammals, for which there is no exact homologue in
the lower extremity.

It has been shown in Chapters XVI. and XIX. that
the terminal segments of each limb present a remarkable
general correspondence with certain constant differences.

1 See Flower, "On the Correspondence between the Parts composing
the Shoulder and the Pelvic Girdles of the Mammalia." — Journal of
Anatomy and Physiology, vol. iv. p. 239, 1870.)

XX.] ANTERIOR AND POSTERIOR EXTREMITY. 373

There can be no question but that the carpus and tarsus,
the metacarpus and metatarsus, and the various dibits
beginning, at the pollex in the one and the hallux in the
other, are serially homologous, or rather homodynamous ;
the circumstance of the constant absence of one of the
bones of the pre-axial digit in both fore and hind limbs is
most significant.

In the carpus and tarsus, the serial homology of the four
bones of the distal row in their respective order is generally
admitted, but with the other bones there is still some differ-
ence of opinion. Gegenbaur has, however, given good
reasons,1 derived chiefly from the results of tracing both
limbs back to their less modified condition in Reptiles and
Amphibia, for considering the astragalus as equivalent
to the scaphoid and lunar united, or the scapho-lunar
bone of the Carnivora, £c. ; the ca'.caneum as repre-
senting the cuneiform, and not, as often supposed, the
cuneiform and the pisiform ; and the navicular of the foot
as representing the os centrale, found only occasionally
in the manus of Mammals.

1 " Untcrsuchungcn zur vergleichenden Anatomic," ltcs Heft,
Carpus und Tarsus, 1864. For a modification of this view see Baur's
suggestion on p. 340.

ADDENDUM.

On p. 90, add to footnote: —

Ruge, " Unlersnchungen uehcr Kntwicklungsvorgange am Bnistlieine
itnd an cler Sternoclavicularverbindung des Menschen." Morpholo-
gisches Jnhrbuch, vi., ]•>. 362, 1880.

Gegenhaur, " Uehcr ilic episternalen Skelettheilc und ilir Vorkom-
nien lx?i den Saugethieron and beim Menschen." Jenaischt: Zeitschrift,
i. p. 175. 1864.

INDEX.

INDEX.

A.

Ar;un (Arrr/nv/a), 96, 182, 275, 349
Ailnrm. 8 1
AUtlara. 85. 349
AUtt (Klk), 83. 197. 298
\MPIIIHIA. 3

Ano^talktritim. 73

Anleater. 47. 61. 64. 68. 75. 88, 102, 103,

111, 114. 229. 230. 333, 333, 359. 305,

3°°. 336, 355

Anlclope, 74. 196, 197, 398, 353
Antelofiid*. i /'

Antitixatra (I'rungbuck), £2, 298

Atmyx. 8 1

Ape. 29. 30. 54. 72, 372

Antitli*. So

Aritomyi (Marmot), 85, 179, 180. 182,

Anttmyx. 81

Armadillo, 29. 39. 47. 61. 64. 68. 75. 76.
104, 107, 113. 114. 231. 232. 259. 260,
278. 283. 306. 307. 308, 324, 336, 342

ARTIODACTYLA, n. 29, 41, 57, in, 192,

29*. Tli 35«>- 35«
Arvicpta. 8s
AteUt (Spider Monkeys). 54, 72, 79, 163,

273, 287
Ainkmiit, 81
Anl^odtit, 86
Avahit. 79
Aye-Aye (Ckirvmyt), 79. 273, 287. 345

!

. 83

Baboon (Cynocrfhalus), 72, 160. 161. 162,

165. 272. 286, 318
HaLrna (Whale), 43. 44, 84. 09, 100, 112.

220, 331, 323, 256, 297. 300, 323, 335.

356

.'laltrHtip/rra. 43, 58. 84. 100. 101, tit, 330,

331, 333, 356. 300, 323, 336

Bandicoot (ftratnelet), 48, 49, 65, 263,

309. 310. 358
Kjttaris, 8 1

Bat, 9, 15. 39. 30. 96, 176. 177. 291, 348

ffathyrrgvi. 85. 179, 180, 183

Bear (Ursui). 55, 68. 72. 81, 167, 168. 274,

287, 388. 330, 331. 346
Beaver (Castor), 26, 68, 73, 85, 96. 180,

181, 183, 183. 254, 375, 291, 392, 321,

33»

Beluga (White Whale), 46, 301. 302
fifrarrftMS, 84
fiettemgia, 88
Bison, 82

Bot(Ox), 73. 74, 82, in, 195, 298. 353
Sosf/afAut. 82
Km'itLr, 196
flraJypodidff, 259
Bradypus (Sloth), 48, 6t, 62, 87, 104, 233,

260, 261, 278, 304, 305. 354
flitfra/HS, 83
Buffalo, 57

CABA«;sot.i (Xfnurus), 88, 307

Cachalot (Physcter), 47, 59. 60. 84, 9?, 99,

113. 217, 218, 219, 255. 301, 302
Camel (Camefus), 41, 47, 83, in, 197, 276,

297, 298, 299. 322
Canidtr. no. 255, 274, 346
Cants (Dog), 20. 27, 37, 38, 55. 68. 80. 94,

117, 120, 136, 139, 143, 144, 148, 173, 192,

247, 273- 288, 317, 331, 346
Cape Anteatcr (Otyctfrofius), 47, 6r, 64,

68, 88, io3, 114. 233, 258, 308, 336
Cape Buffalo, 57
Cape Golden Mole {Chrysochloris), 175,

253. 275, 289
Cape Jumping Hare (Pedetes), 73, 180,

183

Cafra, 83
Cafrtolus, 83, 298
Cafronys, 56, 86. 292. 333
Capybara (Hydroclurtus), 39, 73, 86. 96,

179, 181, 182. 183, 2,2, 349
Cartatus, 83
CARNIVORA. 9, n. 30, 37. 38. 54, 55, 68,

72. 79, 80, 81, 93. no, 166, 173, 176, 248,

255, 273, 287, 288, 289, 320, 325. 331,

342, 346

378

INDEX.

Castor (Beaver), 26, 68, 73, 85, 96. 180.

181, 182, 183, 254. 275. 291, 292, 321, 332
Cat, 167, 172, 173, 346
Catarrhina-, 163

Cavia (Guinea-Pig). 73, 86, 181, 254, 321
Cavy (Coelogenys), 86, 181
Cebidce, 160, 161, 163, 164, 273
Cebus. 79, 161
Centetes (Tenrec), 38, 56, 72, £6, 174, 274,

289, 320, 332
Centetida, 174
( 'ere o fates, 349
Cercoleftes. 81
Cercopitheciis, 78, 165
Cervidir, 196, 298
Cervulus, 83. 353
Cemus (Deer), 40, 83. 97, 257, 273, 237,

334- 352
CETACEA, 7, 9. n, 31,43.58,61, 68, 74 78,

84, 85, 98, III, 2C9, 210, 2l6. 223. 225,
255, 256, 262, 263, 269, 277, 278, 283.284,

299. 301, 302, 312, 323, 335, 368
Cheetah, 173

Chelydra (Water Tortoise), 281
Chimpanzee ( Troglodytes), 37, 53, 54, 67, 92,

no, 160, 161, 251, 286, 318, 331
Chinchilla, 86
CJtirogaleus, 79

( 'hirontys (Aye-Aye), 79, 273, 287, 345
Ckironectes, 89
CHIKOHTKKA (Hats), 9, n, 39. 56. 68, 73,

87. 96, 176, 253, 275, 290, 314, 320, 332,

348

Chlamydopkorus, 75, 88, 232
Cha'ropus, 309, 310, 337, 339, 358
Cholifpus (Sloth), 15, 30, 48, 61,87, l°4>

109, 113, 235, 260, 261, 278, 304, 305,

354
Chrysochloris (Cape Golden Mole), 56, 86,

252, 275, 289. 320
Chrysothrix, 79
Ctrtofffnyf (Cavy), 86, 181
Colobus, 78, 287
Condylura. 251
Connodurtes, 82
Coryphodon, 292
Coypu (Myojotamtis), 86, 179, 253, 275,

332

CREODONTA, 9
Cricetus, 85
Crocidura, 86
Crocodile. 66
Crossarchus, 80
Cryptoprocta, 80
Cyclotitrus (Anteater), 61, 75, 88, 103, 113.

23'. 259> 305, 306' 355
Cynocepltalns (Baboons), 79, 160, 161, 162,

165. 272, 286, 318
Cynti-litrus. 80
Cynomys, 85
Cynonycterts, 96
Cynoptrnis. 87
Cystpphora, 55, 82, 173

D.

Dasypodidte (Armadillos), 47, 61, 64, 68,

104. 107, 113. 259, 306
Dasyprocta (Aguti;, 86, 96, 182, 275, 292,

349

Dasypus, 62. 88, 231, 306, 307
Dasyuridtr, 356
Dasyunts (Dasyure), 89, 239, 279, 309,

325, 326
Deer, 40, 74. 97, 196, 257, 273, 297, 298.

334- 352, 353
Delphinaptents, 84
Delphinida, 46, 217
Ittlphinus (Dolphin), 46, 58, 59, 60, 61, 85.

98, 112. 256, 303
Dendrohyrax, 57, 84
Dendrolaffus ('free Kangaroo), 88, 357
Desmodus, 73, 87
Dicotylfs, 83
Didelphia. 2, 4. n, 48
Didelphida-, 262, 355
Didelphys (Opossum). 48, 49. 65, 76, 89.

239. 3°9, 324, 326, 355
Dinoccras, 292
Dinoccrata, 8
Dipns (lerb-.a) 39, 85, 349
1 )og (Cams). 20, 27, 37, 38, 55,68,94, 117.

120, 136,139, 143, 144, 148, 172, 192,247.

273. 288, 317, 331. 346
Dolichotis, 86
Dolphin. 46, 58. 59, 60, 61, 85. 98, 112, 209,

211, 214, 217, 219, 221, 226. 255, 256, 302,

3°3. 324
Dugong (Halicore), 42. 57, 84, 101, 228.

277. 3°3. 322

E.

F.chidna, 3. 25, 50, 65, 68. 77, 89, 104, 114.
175. 241, 242, 243, 263, 264, 310, 326, 338,

359

Ecliidnidtf, 3
EDENTATA, 6, 11, 31, 47, 61,62. 64,68, j--,,

87, 88, 102, 113, 22Q. 258, 278, 304, 324.

328. 336, 340, 354
Eland, 57
Elephant (_Elephas), 42, 57. 74. 84, in, 148.

201, 203, 205, 227, 258, 292, 293, 294. 322,

328, 335, 368

Elephant seal (Macrorhinns), 82, 284, 347
Elk (Alecs), 83, 197, 298
Ellobius, 85

En/tydraCf>c^ Ouer), Si, 328, 346
Epotnophorus, 87
Equus (Horse), 41, 57, 83.97, IIT> '85. 187,

188, 258, 276, 284, 295, 256, 339, 350,

Erelhizon, 349

Ericitliis. 86, 332

Erinaceidip (Hedgehogs), 174

Erinaceus (Hedgehog), 56, 72, £6,94, 174,

175. 274. 289, 320, 332
F.nplercs, 80
EuTHERtA, 2, 4, 5, 6

INDEX.

379

F.

Felittft. 55. no. 169, 172, 255, 274, 346
/•<•//» 55. 68. 69, 70, 79, 80, i6>, 170, 171,

173. 388. 289
Fiber. 85
Kin whale (Hatifnoftera\ 44, 45, 46, 58,

100, 101, 112, 336
Fl-SSIPCDIA, II

G

o, 54. j). 346. 348

t, 39. 56, 72, 86, 87, 173, 174,

253. 374, 330, 332, 366
GaJictit, 8 1
CaliJia, So
l,azf(la. 8 j
tifHftta, 80
Iftamyt. 85
Georytkui* 85
Gibbon \Hylsbates), 54, 78, 92, no, 160,

161

C.iralTe. 41. 83, 96. 258. 2 (8, 332. 35*
GtoHirfikalMt, 46, 5>, 84. 209,211, 214. 389.

30*. y>3
Glypt xlon, 64
(ionlla (Trvglodylfi}. 37. 53. 54, 67. 78,

93, 93. no. 160, 161, 162, 251. 273. 286,

318. 331

( irampu* (O na\ 46. 84. 302. 103
Guinea Pig (Cavia), 73. 86. 181. 354, 321
Gulo, 8 1
dymnnrn, 73, 86. 174. 289

H.

Halickarnt. 82

HmlUort (Dngonc). 43, 57, 84, 101, 228,

»77- 3°3> 3"

Halitktrium. 47. 323, 336
//«/a/r. 79. 273
Hafalfmur, 79

ftit. 85
Hare i /.</«). IT, 39- 5$ 73- W. 96. 178.

179. 180, 181. i22, 183, 184. 254. *75, 321,

332, 319
Hedgehog (Eri*a(em\ 56. 72, 85, 94, 174,

175, 2:4. 289. 320. 332
Hetnigalta, 80
Hrrfiesln, 80

,
Hippopoumus. 41. 83. 97, 199* 25»i 27°,

296. 297- 334- 352
HOIMP (Man). 78, iff Man
Horse (A><"M)- 4'. 57, 97- "'- l8S- t87-

1 88, 358, 376, 284, 295, 296, 339, 350

Howling monkeys (Myceles\ 36. 37, 55, 93.

160. 161, 163. 164. 165
Jlytma, 55,68, 80, 172, 287, 320

Hyimida, no, 274, 346

Hydrochtrrus (Ofcpybara), 39 73, 86, 96,

179. 181, 183, 183, 292, 349
Ilydrontys, 85
Hydrofiotcs, 83. 298
Hylnba.tei, 54, 78, 93, 93, no, 160, 161
Hyoiiiosckus, 298
Hyfxroodon, 47, 58, 59, 84, 109, 113, 217,

218. 301, 302. 365
Uypsiprymnodon, 357
Hypfipryntnus (Rat Kangaroo), 88, 240,

309. 337

HVRACCHOEA, 8, II, 3OI
Hyrax, 8. 15, 30, 57, 74. 84, in, 201, 202,

258, 277, 292. 293. 334, 340, 3?3
Hystrix ( Porcupine). 73, 86, 178, 179, 182,

'83. 254. 33*i 349

I

Icticyon, 80

Indris, 79

Inia, 46. 58, 302

IKSECTIVORA, 9, 11, 30, 31, 38, 55. 56. 72,

86. 87, 94, 173. 176. 248, 251, 253, 274.

389, 320, 332, 348

J-
JERBOA (/?/>•«), 39, 85. 349

K.

KANGAROO, 48, 49, 65. 76, 88, 235,240,325,

3*6- 35*. 357. 358, 368
Koala (/'fiascolarcttu), 48, 65, 76, 77, 88,

_ii4, 240,337. 358
Kagia, 113. 219
Koodoo antelope, 74, 196

*,

Lagostomits (Viscacha), 86. 180, 182, 349
Lagotkrix, 36. 79, 165
Lamb (Ovis), 313
Lemur, 9. 79, no, 166, 373. 386, 319, 331,

3*5- 346
LEMURINA. 37. 54. 68. 72. no, 166, 173,

287. 345

LEMUROIUEA, ii. 314
Leopard, 55. 69, 70. 173
Ltfiits, 19,39, 56. 73. 86. 96. 178, 184. 254,

375. »93. 3'4- 3*1, 332, 349
Lion, 173. 288
Lizard. 249. 263
Llama. 41, 197, 299
Lontkerts, 56
LopJtiotttfs, 173
Loris, 54, 79. 319

380 INDEX.

Lutra, 81 Mylodon. 87

Lycaon, 80 My odes, 85

Lynx (Felis), 72, 173 Myogale (Water Moles), 38, 86, 175, 320,

348

Myopolamus. (Coypu), 86, 179, 253, 275,

M. 332

Myrmecobws, 89

Macacus, 78 Myrniecophaga (Anteater), 47, 61, 6?, 63,

Macraitchenia, 41 87, -102, 103, 113, 229, 230, 259, 305, 336

Macropidie. 357 Mymtecophagida, 259

Macrofns (Kangaroo), 48, 49. 65, 76, 88, Mvsi ACOCETI. 43, 99, 219

239, 240, 309. 325. 326, 339, 356, 357, Myxopoda, 348
358

Macrorhinus (Elephant Seal), 82, 284, ,^T

347

Macroscelid* (Elephant Shrew). 56. 173. Narwha|e (Monodon), 46, 84, 301, 302

M174;/74' 3f°^ Nasalis, 78

Man (Homo), 26. 30. 36, 37, 51, 67. 72, 02- Xasita s=; 81

108, 120, 132, 150, 163, 240, 270, 271, 272, Weotrueu* 1-7

273,284,317,331,343.368 Nvcteri* s'«

Manatee (,)/«»«//«), 26, 42, 43, 57- 64, A%c//«"j« s

IO2, HI, 223. 224. 228, 278, 323 fj f.-fi

Mam's (Pangohn or Scaly Anteater), 31, WttflU ins, 79

47, 61, 64, 75, 76, 88, 102, 232, 259, 304,

308 O.
Marmot (Arctoinys), 85. 179, 180, 182, 292

MAKSUPIAI.IA, 2. 4, n, 23, 29, 31. 48, 65, Octndon. 86

68, 76, 77, 88, 89, 104, 114, 235,241, 261, ODON rocirn, 46, 98, 107, 112, 209, 255,

278, 309, 324. 325, 337. 355 3<«. 3°'- 336

Megaderma. 87. i;8. 332 Opossum (Diaflfhyt) 48, 49, 65, 76, 239,

Megaptera, 46, 112, 256, 277, 300. 335 309, 324. 326, 355, 358

Megatherium, 62, 75, 87, 260 Orans; (Simla), 37. 53. 54. 67, 92, 93, no,

Meles. 55. 81 160, 161, 162. 286. 287, 328. 344

Jlfcllivpra, 55, 81 Ore a ((irampus), 46, 84. 302, 303

MellirstlS.Sl OKMTHOUKLI'HIA, 2, 3, II, 50,246, 248,

Menopoma, 66 249

Mephitis, 55. 8 1 Ornithorhynchus, 3. 20. 50, 65, 68, 77, 89,

Mrsp/>l<>i/<y>i. 84. 301 U'4. 10;, 114, 243, 262, 264,311,326, 337,

Mesothetium, y 338, 340, 358. 359

Metat/u-ria, -2, 4 Orycteropus (Cnpc Ante.-iter), 47, 64. 68,

Microgale, 31, 73, 86 76, S8. 102, 114. 233, 258, 308, 324, 336

Midas, 79 Oryzoryftcs. 289

Mimofitcrus, 87 Otaria (Eared Seal), 55, £i, 82. 255

Mole (Talpa\ 38, 56, 86, 95. 175. 246, 251, Otariittif, (Eare.1 Seal-), 173, 289, 347

274, 275t 289. 290, 314, 320, 348 Oft'cyt»i, 80

Molossimr. 332 Ovifus, 82

Molossus, 87 O~'is (Sheep), 82, 192, 19;, 298, 313, 353

Monkeys (Siii'iina), 54, 55, 72 93, no. Ox (/>'<>$), 73, 74, 82, in, 195, 298, 353

159, 160, 161, 162, 163, 164, 165. 273, 287,

3i8

MONODELPHIA, 2, 6, 7, II
Monodon (Narwliale), 46, 84, 301, 302

MONOTREMATA, 2, 4, II, 23, 25, 50, 65, PACA, 182, 183

68, 77, 89, 104, 107. 114, 241, 262, 279, Paltrotherhtm, 215

310, 314, 32^, 328, 338, 358, 360 J'aiiH' lin (Ji~ finis), 47, Ci, 64, 75, 76. 10.-,

Norinops, 178 232, 259, 308

Moschns (Deer), 74, 83 Paradoxurus, 72. 80

Mns i Rat), 85. 96, 180, 182, 2^2, 349 Pecari, 258. 296, 352

Mtiscardirtns. ^-5 PECOKA, n, 39, 199, 257, 298, 321, 322,

Mnstela (U easel), 55, 80, 81, 169 334, 339, 353

Musteliihr, no, 169, 274, 346 Pt-detes (Cape Jumping Hare), 73, 85, 180.

Mycetes (Howling Monkey), 36, 37, 55, 79, 182

93, 160, 161, 163, 164, 105, 273 Ferameles (Randicoot), 48, 49, 89, 262,

My dans, 81 309, 310, 358

INDEX.

rtrameliJa, a6a, 309, 337, 358
PERISSODACTYLA, n, 30, 41, 57, m, 185,

aoi, 758, 294, 296. 298, 322. 328, 333, 350,

35'
Ptrodicticia (Potto), 55, 79, 286, 287, 319,

345

Petaurus, 88
Pttrodramus, 774, 348
Pkottxkftrtts, 83
1'kala.Hgist* (I'halanger). 48, 76, 88, 309,

337. 357, 358
rkascogaU, 89
J'katcotarclot (Koala), 48, 65, 76, 77. 88,

"4. 240. 337, 358
Pk*stolomys (Wombat), 48, 49. 65, 68. 76,

77, 88, 114, 240, v6j, 267, 278, 309, 325,

328, 355
I'tuxa. (Seal), 55, 68, 72, 8j, 173, 255, a<;6,

274- 284. 289, 319, 328, 331, 343, 346, 365,

367, 368

Pkixtrna (Porpoise), 46. 71, 84, 98, 112
1'kyllorkina, 87, 321
1'kyllorkinina (l^af-nosed Bat), 348
i'ltyilaiti'mit&r, 291
Pkystttr (Cachalot or Sperm Whale). 47,

59, 60, 84, 98, 99, 113, 217, 218, 219, 255.

301, 502

Pkytttrridir, 59, 113. 217
Pig (Sat), 26, 41, 83, 97, 146, 147, 175, 197,

199, 244. 2jB, 296, 297, ^22, 3J3, 352
Pike Whale (ll.ila-H^fttra). too
I'l.ssiPEUlA, it. Si, 82, 94, no, 255, 274,

289

Piptstrtllits, 253
Pitkecia, 79
f'latamitta (Sousou), 43, 46, 84, 217, 256,

263. 302, 324
Pliityrrki*<r, 163
Polar Bear ( Urtui), 167
Pontapcritt, 46, 217
Porcupine {Hyttrijc). 73, 178, 182. 183, 254,

349

Porpoise (Phofcrna), 46, 71, 84, 98. it 2
J'otami'fa/f. 38. 73, 253. 789, 320
Potto (PeraJicticHs), 55, 79, 286, 187, 319,

345
PKIMATKS. 9, n. 32, 36. 53. 78, 79. 92.

109, 150. 159. 249, ^7'. '85. 3'6, 33'. 343
Priodan (Armadillo), 75, 76, 88, 104, 114,

260. 307, 308
PKOSOSCIDEA, 8, ti, 42, 203, 223, 2;6,

354

Ptvcjftm. 55, 81

Prtxytntidte, no, 169, 274, 346
Prongbuck {AntiLKapra), 298
Prattles. 68, 80
I'KOTOTHKKIA. 2, 4, 5
/'sfui/arca, 46, 84
Pttropidtt, 291
Pteropus, 68, 73, 87, 96, 176, 177, 253, 230,

33*

Pudu, 353
Pittiua, 83
Puma, 68, 173

R.

Rabbit (Letus), 254

Rangi/er (Reindeer). 83, 298

Rat (Mus), 96, 180, 182, 292, 349

Red Deer (Cervus), 40, 97, 257, 273, 297,

334. 352
Rhinoceros, 41, 57, 83, 84, 98, in, 189,

190, 191, 201, 276, 295, 296, 333,350,351,

Rninolopkida, y\

Rhizoniys, 85

Rhyntkocyoit, 56, 73, 94, 173, 274. 289,

3*9. 348
Knytina, 42
RODENTIA, 8, n. 29, 39, 56, 57, 68, 73, 85,

86. 96, 178. 179, 180. 181, 201, 248, 253,

275. 293. 321, 328, 332, 340, 342, 348, 349,

368
Rorqual ( Rakmoptera), 44, 100,112,220,

221, 277, 300, 323

RfMINANTIA, 96, 196, 276, 298

Saiga. 82. 196

Saimtrii, 160

SACKOPMDA, 3. 4, 50

Sfa/afs. 251

Scaly Anteater (Manis), 31, 47, 61, 64, 75,

76, 88, 102, 232. 259, 308
Sciurus (Squirrel), 85, 179, 180, 292, 332,

349

Sciurofterus, 85

Sea Bear or Sea Lion (Seal). 173, 367
Seal (P/ioca). 55, 68, 72, 82, 173, 255, 256,

274. 284, 289, 320, 328, 331, 343, 346, 365,

367. 68
Sea Otter (

•(Enhydra\ 81, 328, 346
Stmnofithecus, 72, 78
Sheep (Ovis), 82, 192, 193, 298, 353
Shrew (Sorex), 38, 39, 56, 94, 95, 175, 176,

252, 289, 314, 320
Siamang ( Hylobates), 93, 160
Simia. (Orang), 37, 53. '54. 67, 78, 92, 93,

no, 160. 161, 162, 286, 287, 328, 344
SIMIINA (Monkeys), 72,110,159, 160,161,

162, 163, 164, 165, 273, 287, 318, 343,

345
SIKENIA, 7, 9, n, 23, 42, 57, 69, 75, 84,

lot, in, 223, 256, 277, 303, 312, 322, 336,

368
Sloth,/*' .3, 61, 62, 68, 75, 104. 107, 109,

113, -,.33, '235, 248, 259, 260, 261, 278, 304,

324, 328. 336, 354, 366
Solenodon, 73. 86, 289, 332
Sorex (Shrew), 38, 39, 56, 86, 94, 95, 175,

176, 252, 289, 314, 320
Soricida. 56, 175, 252
So!al a, 84
Sousou (Platanisla), 43. 46, 84, 217, 256,

263, 3°2. 324
Spalax, 85

382 INDEX.

Spermophilns, 85 Tupaia, 56, 73, 173, 174, 289, 320, 332

Sperm Whale (I'/iyseter), 47, 59,60, 84, 98, 7'tirsiops, 84

99, 113, 217, 218, 219, 255, 301, 302 TYLOPODA, n, 41, 197, 294, 298, 334, 353
Spider Monkey {A teles), 54, 72, 79, 163,

273, 287 .,

Squirrel (Scinnts), 85, 179, 180, 292, 332,

Stotorkynch**, 55, 82 U£OU''ATRA' 8'"' 20> 24' 39, 57- 68, 73,
SuBUNGULATA.292 82' 83- 84, 96, no. i8S, iy8, 199, "|.

SUINA. it, 41, 296, 298, 352 "5. 24-, 257, 276, 29,, 29.,. 32,, 3<8,

Suricata.Zo 333-334-349

Sus (Pig), 26, 41, 83, 97, 146, 147, 175, 197, 77 ,'R"0\ l69' «iS5' 27t 346, ,0

•* ™ ~ ™ »- '•• 7" '" l6" l68' ""

}'csf-crngo. 39. 87
Talpa (Mole), 38,56, 86, 95, 175, 24^, 251, Viscacha (La^ostoinus), 86, 180, 182, 349

274, 275, 289, 290, 314, 320, 348 ViTerra, 55, 80, 314

Tamandua, 87, 231, 259 I'ircrritite, no, 171, 172, 274, 356

Taimas. 85
Tap.r ( Tapiriis), 41, 57, 83. 97, 98, in, 191, ^.

225. 258, 276, 295, 333, 350

7^2::'79?°.66, 3.9, 345, 346 *M-«F, (T"'?,"?*' ¥' ***> 3"7' *7

T t r/^ X QQ / " Weastl (Alnstela)t ss, 80, 81, 160

JlltltSHl, 47, 00, *Oj M'U i > -.- ,

Ta vitieti 81 V h:lle> 43> 44> 45> 4(S> *?' s8' 5<>- 6o' 8'«- 9R-

Ttnrec (Ctntetes), 38, 56, 72, 36, .74, 274, 59, •«>, ^«, m. "2, 2,7, 220, 256. 2yQ,

7VaS^.3i« ^^ &3M^«>«f <6. 3d. 302

Theropitkcms, 79 Womh^t (I'***™'™?*), 48. 4.,, 65. 68, 76.

Thylacine (Thyladnnt), -48, 49. 77, 89, 77-8 8. 114, 240, 162, 267, 278, 309, 325,

235, 236, 237, 238, 309, 325, 326, 356
Thyroptcra. 348

Tiger, 68, 16;, 170, 171, 173 X.

7 olypeutes, 88. 308

Tortoise. 179, 281, 366 .\\-nurtis (Cabassou), 88, y.j

Tojcodon, 9, 192

TKAGUI.INA. n, 41, 197, 298, 334, 353

Tragulus, 83 Z.

Tree Anteatcr (f'yflotunis\, 103. 3r6, 355
Trichechus (Walrus), 55, 82, 347, 367 7.apns, 85

Troglodytes, 37, 53. 54, 67, 78, 92, 93, no, /.iphiimr. 218

160, 161, 251, 286, 318, 331 Ziphius, 59, 113. 217

NAMES OF AUTHORS WHOSE PAPERS AND
WORKS ARE REFERRED TO.

Alhrtcht, 134, 155, 344, 171
lialfour, 145. 147, j6i
Uardeicbtn, 340
Baur, 298, 340, 349

IJUmvillr, 2

Boo.*. 296

Bnndl, 201

Brooke, Sir V.ctor. 298, 353

Callcruler, 155

Coue*, 362

DotMon, 176. 291

I»ollo, 134

Doran. 133

Kschrichl, 335

Flower, 77, 190, 301

Kraser. 134

Ciarrod, ac8

Gcgenbaur, 133, 245, 371, 281, 2^6, 314,

. 3*'. 374
(roctie, 361
(irubcr, 284
Humphry, 61
Huxley, 2, i ji, 133
KAU, 326

Koelliker, 133

Krause, 314

l.eboucq, 284

Lcche, 314

M.icuns, 361

Milne-Kdwards, 179

Mivart, 37,280, 286, 361

Parker, 90, 93, 98, 102, 133, 145, 245

Peters, 133

Keichert, 133

Keinhardt, 335

kolleston, 361

Rosenberg, 284

Huge. 374

Sabatier, 361

Salensky, 133

Strasser, 361

Struthers, 44, 284, 335

Thomson. Allen. 283

Turner, W. , 45, too, 112, 244, 301

Turner, H. N., 141

Weyhe, 316

Wilder. 287

Wyman, 362

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