MR. W. K. PARKER ON THE OSTEOLOGY OF BALANICEPS REX. 335 
bridged over by a thread of bone near its outer end, bring us to the last sacral vertebra. 
This bone is united by its centrum to the centrum of the one before it, and by the tips 
of its coalesced ribs (which turn forwards near their ends) to the iliac bones, now 1+ 
inch apart. The pleurapophyses of this last sacral are one third of an inch longer than 
its diapophyses ; these latter processes are bevelled at their ends, so that the transverse 
process is suddenly smaller where it is only composed of a rudimentary ‘rib.’ The 
neural canal can be seen between the two last sacrals. The counterpart of this last 
sacral vertebra of the Baleeniceps forms the first of the caudal series in the Heron and 
the Adjutant ; and perhaps this would be the case in the next Balzniceps that should 
be dissected. The structure of the caudals is extremely like that of the last sacral, but 
they gradually acquire short neural spines, the last compound ‘ ploughshare bone’ (which 
is composed of nine or ten embryonic vertebrz) being sharply carinate along nearly the 
whole of its upper margin. The ends of the coalesced caudal pleurapophyses project 
three lines below and external to the ends of the diapophyses, and are blunt, smooth, 
and clubbed. In the last three these transverse parts are gradually lost, whilst they 
gain on their inferior surface small forward-projecting coalesced ‘ hemapophyses’ (hypo- 
- physes of Huxley). A small distinct ‘sesamoid bone’ of this nature lies between the 
second and third centrum, and belongs to the latter. Thelast caudal is one inch and 
two lines long, measured along its base. These caudals of the Baleeniceps have a very 
beautiful structure. They are not oily as in the Heron, but pneumatic as in the Ad- 
jutant ; and the air enters them principally by a large oval opening, which in the two 
first joints occupies the entire front of the broad basal part of the compound transverse 
process ; this large recess communicating by apertures with the whole of the interior 
of the bone. The external table of bone is extremely thin, the threads and areolar 
plates of diploe are delicate in the extreme, and the short diverging ‘ribs’ are mere 
hollow tubes, having extremely thin walls. 
Pelvis. (Pl. LXVI. fig. 1721, ism, pb; and Pl. LXVII. figs. 2 & 3.) 
The pelvis of this bird is very pleasing both to the anatomist and to the systematist. 
It has little in it even of a generic nature to distinguish it from that of our native grey 
Heron, and indeed, of all the true Ardee and Botauri: it might belong to a gigantic 
form of Ardea proper. 
If this ‘ stranger in a strange land’ (too early lost to the zoologist to gladden pre- 
maturely the anatomist with its rich spoils) had lived as long as the four Grey Herons 
did, whose bones now lie before the writer, the difference between their pelves would 
have been chiefly a difference of size. The comparative smoothness of the bone and. 
its softer and more rounded outline would, with the lapse of years, have given it that 
sharpness and angularity which is seen in these Herons’ pelves, arising from the strong 
crests on the margins of the iliac bones. The upper margin especially of each iliac 
bone as it diverges to overhang the acetabulum, and then form the upper and outer 
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