MR. W. K. PARKER ON THE OSTEOLOGY OF BAL.ENICEPS 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 IJ 

 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 Balceniceps forms the first of the caudal series in the Heron and 

 the Adjutant ; and perhaps this would be the case in the next Balseniceps 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 vertebrae) 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 ' haemapophyses ' (hypo- 

 ' physes of Huxley). A small distinct 'sesamoid bone' of this nature lies between the 

 second and third centrum, and belongs to the latter. The last caudal is one inch and 

 two lines long, measured along its base. These caudals of the Balseniceps 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. (PI. LXVI. fig. 1 il, ism, pb ; and PI. LXVH. figs. 2 & 3.) 

 The pelvis of this bird is very pleasing both to the anatomist and to the systematise. 

 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 Ardew 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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