376 
transverse processes, and the first eleven have 
also spinous and articular processes. The 
transverse processes are broad and depressed ; 
they gradually increase in length to the tenth 
caudal, then as gradually diminish to the twen- 
tieth; their extremities are expanded, and, 
from the fifth backwards, are thickened and 
tuberculate. The spinous processes progres- 
sively diminish in height from the first 
caudal. The first six caudal vertebre have 
both posterior and anterior oblique processes, 
and are joined together both by these and by 
the articular surfaces of the body: the anterior 
articular processes are present, but age 
sively diminish in size from the seventh to the 
sixteenth vertebre, and are not subservient to 
their reciprocal articulation. Inferior be seg 
processes are developed from the bodies of 
the third to the nineteenth caudal vertebra 
inclusive; but there are no hemapophyses 
articulated to the vertebral interspaces, as in 
many Marsupials and the Edentata. In the 
Echidna the inferior spinous processes are 
absent ; but rudiments of hemapophyses are 
connected with the interspaces of one or two 
of the middle vertebra of the tail. The cau- 
dal vertebre in the Ornithorhynchus are of 
nearly the same length to the two last; they 
progressively diminish in vertical diameter as 
they recede from the trunk, and are chiefly 
remarkable for their breadth and flatness; 
resembling in this respect, as Cuvier has ob- 
served, the caudal vertebre of the Beaver, and 
we might add those of the Cetacea; the hori- 
zontally extended tail having a similar relation 
to the frequent need which an aquatic animal 
with hot blood and a quick respiration of air 
has to ascend rapidly to the surface of the 
water. 
Of the pectoral extremities —Cuvier* justly 
observes that the most remarkable part of the 
osteology of the Monotremes is the organiza- 
tion of the shoulder; which corresponds with 
that of birds, and still more with that of 
lizards. 
Had these anomalous Mammals been ex- 
tinct, and their fossilized skeleton alone, as in 
the Ichthyosauri, been preserved for the con- 
templation of the naturalist, the perplexity 
which the combination of this structure with 
the mammalian conditions of the skull and 
vertebree would have occasioned may be readily 
conceived. 
The scapula (/) is represented detached, with 
the coracoid (0), at G, fig. 173; /* is the 
cartilage appended to the short convex base. 
The scapula is long, narrower than in most 
Mammalia, and has its posterior vertebral 
angle so much produced, as to give it a re- 
semblance to the scapula of the bird and 
saurian: this resemblance is farther increased 
by the origin of the spine close to the anterior 
costa, and by the spine being bent forwards 
so as to seem to form a continuation of the | 
external surface of the scapula, which is thus 
rendered concave in the Ornithorhynchus. 
* Ossem. Foss. v. pt. 1, p. 146. 
MONOTREMATA. 
The spine, however, terminates in a freely pro- 
jecting acromion. F 
The true anterior costa is, in this Monotreme, 
represented by a ridge which traverses ob- 
liquely the inner and convex side of the sca- 
pula, from the anterior vertebral angle to the 
neck of the bone. In the Echidna this ridge 
is nearly obsolete, and the spine of the sca- 
pula is bent so as to form a ments con- 
tinuation of body of the scapula wi 
of which it is nearly parallel : the sotonsie aa 
mination is slightly twisted. a 
Both Cuvier and Meckel describe the 
nous process of the scapula as the anterior 
margin, (superior costa in human ra 
and consequently consider the spine of th 
scapula as being absent. Cuvier says, “ Le 
bord antérieure descend presque droit jusqu’a 
Vendroit ou il se courbe en dedans pour former 
une apophyse, qui porte la fourchette.” Meckel 
recognises this process as the acromion : “ Margo 
anterior partis superioris versus inferiora ex- 
trorsum primo flexus, dein eminentiam, acro- 
mion, antrorsum et introrsum versam, emittit.” 
The ‘ margo anterior’ of Meckel, * bord anté- 
rieure’ of Cuvier, is, in fact, the true spine of 
the scapula, and the true ‘ margo anterior’ is 
the ridge above described. The proof of this 
is afforded by the origin of the supra-spinatus 
muscle which occupies the s between 
Meckel’s ‘ margo anterior’ and the ridge 
which I regard as the true anterior costa, and 
which is not noticed by either of the anato- 
mists above quoted. 
Since the scapula is peculiarly characterized 
in Mammalia by the presence of a spine and 
in Ovipara by its absence, its recognition in 
the Monotremes, under the modification 
which its apparent absence is occasioned, 
the transition to the oviparous type of this bone 
is effected, becomes a subject of especial in- 
terest. 
The whole scapula is broader, thicker, and 
less curved in the Echidna than in the Orni- 
thorhynchus. In both Monotremes, the pos- 
terior margin or costa is concave, most so in 
the Ornithorhynchus, and in both it is turned 
towards the trunk, so that the sub-scapular 
surface looks obliquely forwards and inwards. 
The articular surface is divided into two facets: 
the one, internal and flat, articulates with the 
coracoid; the other, external, is sligh’ 
the glenoid cavity for the humerus. meres 
The coracoid (fig. 173, G, 0) early coalesces 
with the scapula in the Ornithorhynchus; it main-= 
tains its independent condition to a later 
in the Echidna. In both it is a strong, su 
pressed, subelongate bone, expanded at both 
ends; one of these is articulated and anchylosed 
with the scapula, as above described; the other 
is joined to the anterior and external facet of the 
manubrium sterni. The posterior margin of 
the coracoid is concave and free; the anterior 
margin is straight and articulated with a thin’ 
broad irregularly quadrilateral jar of bone in 
the Ornithorhynchus, and a thicker and nar- 
tly con- 
cave, and contributes, with a similar but nar 
rower concave surface of the coracoid, to form 
