MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE. 345 
series almost equalling the hinder ones in importance. On the thirteenth vertebra arti- 
cular facets are faintly indicated on the anterior edge only. 
Having now examined the modifications of the different parts of the caudal vertebre, 
their bodies, neural arches, transverse processes, arterial foramina, and articular facets 
for heemapophyses, a few words must be said on the peculiarities of the different vertebree 
of the hinder part of the series taken as a whole. 
The first twelve, or chevron-bone-bearing vertebra, present a gradual and steady 
change in size and general character from first to last, this change consisting of the 
gradual reduction in size of the centrum, reduction of the neurapophysis, and reduction, 
to absolute disappearance, of the transverse processes. In the thirteenth caudal vertebra, 
a great change takes place in the size of the body, though the same general form is 
maintained. The anterior and posterior surfaces are nearly subcircular ; but the absence 
of any transverse processes, and the presence of a roughened low tuberosity representing 
the neurapophysis, and of the inferior tuberosities for the attachment of the hemapo- 
physes, make the whole bone higher than broad. The most remarkable feature about 
this vertebra is the rapid manner in which it diminishes posteriorly, the posterior sur- 
face for the attachment of the intervertebral substance being 2” less in diameter than 
the anterior. ; 
Twelfth and seventeenth caudal vertebra. 
The succeeding vertebra is of very simple character, being reduced to a centrum with 
a slight tubercle covering the neural canal to represent the spinous process; in conse- 
quence of this, the whole bone is still slightly higher than broad. After this a sudden 
change in form takes place; in the fifteenth and all the succeeding vertebre the breadth 
predominates over the height. The fifteenth to the twentieth inclusive present very 
uniform characters. ‘They may be described generally as transversely elongated oblong 
bodies, flattened before and behind, above and below, and at each side. The upper 
and under surfaces are remarkably alike, so much so that it requires close attention to 
very minute characters to be able to distinguish them. ‘The upper surface shows on 
each side, about midway between the median line and the outer edge of the bone, the 
funnel-shaped opening of the large circular arterial canal, which perforates the vertebra 
nearly vertically. The quadrangular space between these perforations bears at each 
corner four tuberosities, an anterior and a posterior pair, remnants of the neurapophysis, 
