98 MR. W. H. FLOWER ON THE OSTEOLOGY OF 
suring *5", the sixth ‘9’, and the last 1:2”. Their arches are surmounted by rather 
long, erect, and (especially in the hinder part of the region) very broad spines trun- 
cated at the top. The antero-posterior breadth of these processes presents a constant 
relation to the length of the body, being always nearly equal with it, and forms rather 
a remarkable feature in the general aspect of the vertebral column. The height of the 
spine of the first thoracic vertebra is scarcely inferior to that of the others, which are 
almost precisely equal. In the sixth, from the inferior edge of the body to the junc- 
tion of the lamine of the arch measures 1:6"; the spine above this point is 2-2". 
Distinct articular facets or zygapophyses are developed on both the anterior and pos- 
terior edges of the arches as far as the ninth vertebra, and on the anterior edge only of 
the tenth and eleventh. These, as usual, are broad and wide apart at the commencement 
of the series, and gradually become narrow and approximated as they shift from the 
sides to the summit of the progressively diminishing neural arch. 
The so-called oblique processes (metapophyses of Owen) begin to separate them- 
selves from the transverse processes at the fifth or sixth vertebra, and gradually 
pass upwards and inwards on the anterior edge of the arch towards the prozygapo- 
physes, which they supersede on the twelfth vertebra. Owing to the comparatively 
slight development both of these processes and the zygapophyses, the thoracic vertebre 
of Inia are not locked together in the manner which distinguishes those of Platanista. 
It remains only to speak of the processes for the articulation of the ribs, which offer 
some interesting peculiarities. In all the ordinary Delphinidw the anterior ribs are 
articulated by their tubercle to a well-developed transverse process standing out from the 
side of the arch, and by a long neck to the hinder edge of the body or root of the arch 
of the antecedent vertebra. ‘There is usually no indication of any articular surface for 
the head of its own rib on the front edge of the body of the vertebra. At about the 
middle of the series the heads suddenly cease to be developed, and the rib is only attached 
by its tubercle to the end of the transverse process, still arising from the arch, but 
gradually lengthening and becoming lower in its point of origin, till at the end of the 
series it springs rather from the body of the vertebra than from the arch, and is in a line 
with the transverse processes of the lumbar vertebree. This arrangement, departing con- 
siderably from that found in the ordinary mammal, occurs in Delphinus, Phocena, Orca, 
Globiocephalus, Beluga, Monodon, and their immediate allies—in fact, in all the Del- 
phinide which have ossified costal ribs. In the remarkably aberrant Hyperoodon and 
Physeter a totally different arrangement takes place in the hinder part of the dorsal 
region, which, however, is equally peculiar among the Mammalia. The upper transverse 
processes springing from the arch (diapophyses, Owen) suddenly cease, and the rib retains 
its connexion with the body only: the articular surfaces of the latter push out a process 
(which, on Owen’s system, would be called a parapophysis), at the end of which the rib - 
is attached, and which becomes the transverse process, being continuous serially with the 
transverse processes of the lumber region. In the first case, the transverse process on the 
