1865.] AXIAL SKELETON IN THE PRIMATES. 569 
In all the Simiine the transverse diameter is still considerably in 
excess, exceeding the vertical depth by from about one-fourth to a 
little under one-third of the latter. 
In Indris the transverse diameter is also decidedly in excess, 
though to a less degree, and it is so also in Ateles and even some- 
what in Mycetes; but in all the other genera the vertical depth 
equals, or more or less decidedly exceeds, the transverse diameter of 
the thorax. 
Having now reviewed the different regions of the spine, we may 
consider certain parts not as confined to those regions, but as ex- 
tending throughout the vertebral column; and, first, the 
NEURAL SPINES. 
These processes attain both their greatest absolute and relative 
length in Troylodytes and Simia, but above all in the Gorilla. 
On the other hand, they are wanting in all caudal vertebree* but 
a very few, and also in some of the cervical vertebrae of Galago and 
Cheiromys. 
Generally it is the seventh cervical and most anterior dorsal ver- 
tebree which bear the most elongated spines ; but, besides Troglodytes 
and Simia, Perodicticus and Arctocebus form exceptions, and Tarsius 
also, in which the longest neural spines are sacral, or in the most 
posterior part of the lumbar region. 
The spines of the trunk vertebree are vertical, or directed back- 
wards, in Man, the Simiine, Ateles, and the Nycticebine; but in 
all the other genera of the order the spines of the more posterior 
vertebrze are inclined forwards, the change of inclination taking 
place sometimes (e. g. Hapale) at the tenth, sometimes (e.g. Chei- 
romys) not till the thirteenth vertebra. 
The amount of inclination of the spines of the posterior trunk 
vertebree reaches its maximum in the lower Cedzda, in Hapale, and 
in Lemur. 
The summits of the spinous processes are often more or less flat- 
tened. This is generally very marked in the lumbar vertebre of 
Troglodytes and Simia, also in Macacus, Inuus, and Oynocephalus, 
and to a less degree in Hylobates, Ateles, Indris, and others. 
In all forms the antero-posterior extent of the spinous processes 
of the anterior region of the trunk is less than in those of the more 
posterior portion ; but this increase is least in Man and the Simiine: 
in all the rest (the Wycticebine in this forming no exception) it is 
much greater. 
Occasionally the antero-posterior extent of the summit consider- 
ably exceeds that of the part below, so that the spinous process may 
almost be said to bifurcate antero-posteriorly +. 
* In Afeles the first five caudal vertebrz support spinous processes ; and some- 
times even the sixth does so. 
+ This is well seen in the dorsal vertebre of Cercopithecus albogularis (no. 176) 
in the Osteological Collection of the British Museum, and to a less degree in an- 
other individual (no. 17 /) in the same collection, as has already been mentioned. 
Proc. Zoou. Soc.—1865, No. XXX VII. 
