MR. W. K. PARKER ON THE OSTEOLOGY OF BAL^ENICEPS REX. 331 



the two posterior pieces. In the second dorsal the two hinder processes are rather 

 nearer the anterior end of the centrum, and are now evidently only one bifurcating 

 piece. In the third dorsal this piece is losing its lateral processes ; in the next three 

 vertebrse they have become simple and further backwards in position, whilst in the last 

 joint, that which articulates with the sacrum, this mesial process has vanished. 



Retaining the familiar and valuable term ' parapophysis ' for all these processes, we 

 would distinguish the most marked varieties by a prefix, which should indicate their 

 place and function. Thus Pre-parapophysis will indicate in birds that process which is 

 anchylosed above to the rudimentary rib, and which sends down a spur of bone below 

 to form half the carotid canal ; in Ophidia it may be seen as a short and blunt spur 

 beneath the articular diapophysis. 



The posterior outstanding processes below the lower cervical centrums in the Penguin, 

 Cormorant, and Fowl, and the pair of processes which form an open haemal canal in 

 the true Ophidians, and a closed canal in the Blind-worm, may be called Post-parapo- 

 physes. 



The single inferior median process, so common in the centrums of the Vertebrata, 

 can take on the prefix hypo ; then, instead of hypapophysis, we shall have hypo-parapo- 

 physis. The caudal haemal spine in the little Anguis fragilis, and in those fishes where 

 there is no sign of its being anything but an exogenous growth from the down-bent 

 parapophyses, may be termed a meta-parapophysis. Lastly, where this lower trans- 

 verse process arises from near the middle of the side of the centrum, as in many 

 osseous fishes, no prefix need be used : it is simply a parapophysis. 



Professor Huxley shows that the ribs themselves, and the ' chevron bones ' of the 

 caudal vertebrae of many of the higher Vertebrata, are all developments of the ' centrum,' 

 but having a distinct ossific centre'. 



Several of the middle cervical vertebrae have perfectly bony carotid canals in the 

 following genera — viz. Balaniceps, Cancroma, Ardea, Botaurus, Mycteria (M. australis), 

 Pelecanus, Sula, and Picus ; the number is variable in skeletons of the same species, 

 being greatest in old birds. However, as a rule in the class of birds, the mesial part of 

 this canal is completed by interosseous membrane. 



Dorsal Vertebra and Ribs. (PI. LXVI. figs. 1 & 7.) 

 The four true dorsal vertebrae of the Balaeniceps are quite distinct from each other 

 and from the sacrum. In the Pelican, and in one of the Humming-birds, the Mango 

 Colibris {Trochilus colibris), the last two dorsals have entirely coalesced with the 

 sacrum ; that they are dorsal and not sacral vertebra; is proved by their anterior posi- 

 tion with regard to the iliac bones, the true sacrals being over-canopied by these large 

 ' pleurapophyses.' 

 The neural spine of the first dorsal is the longest, being seven-eighths of an inch in 



' Croou. Lect., pp. 48 and 71. 



