OSTEOLOGY OF BIRDS 2/ 



nunculus sparverius and Polyborus tharus 

 at least four of these vertebrae form one solid bone in the adult 

 specimen ; in Micrastur brachypterus there are again 

 five dorsals, and all independent segments. 



Sharpened ridges beneath the transverse processes connect the 

 facets for the capitula and tubercula of the ribs ; this feature is 

 best marked inCarthartes a. septentrionalis and 

 next in Gyparchus papa, less so in the others. 



Vertically elongated but shallow depressions occur above the cen- 

 tra on the anterior and posterior margins of the neural spines, for 

 the insertion of the broad connecting ligaments ; the spines them- 

 selves spring almost abruptly from the neurapophysial arch, are uni- 

 formly quadrate plates of an equal hight, with thickened crests 

 above, that become united at their anterior and posterior ends by a 

 modified arrowhead joint, such as we see in the owl Speotyto, where 

 the points are more acute. 1 



1 Before closing what we have to say about the spinal column, I wish to footnote 

 here my views of many years ago upon the question as to where the division should 

 be made in the cervicodorsal region of the spinal column. It is from my Osteology 

 of the Cathartidae and I said: " The manner in which the vertebral column of birds 

 should be divided has been differently viewed by ornithotomists. The two principal 

 reasons for this difference- of opinion, no doubt, has arisen from the various arrange- 

 ments assumed by the free ribs at the anterior part of the column, and the equally 

 diverse manners in which the innominate bones of the pelvis attach themselves to the 

 column. Without entering very extensively into the literature of the subject, let us 

 first examine into the question as to where the line shall be drawn between the 

 cervical and dorsal vertebrae. We seem to have presented us here two very uncer- 

 tain guides; the first being whether the first free ribs are connected with the sternum 

 by sternal ribs or haemapophyses, and the second _ upon the character of the vertebrae 

 — ■ that is, whether they have the appearance of dorsals, as we commonly find them, 

 or cervicals as we usually recognize them." Professor Huxley sharply defines the 

 line when he says: " The first dorsal vertebra is defined as such by the union of 

 its ribs with the sternum by means of a sternal rib; which not only, as in the 

 Crocodilia, becomes articulated with the vertebral rib, but is converted into complete 

 bone, and is connected by a true articulation with the margin of the sternum." 

 [Anat. Vert. Animals, p. 237] Professor Owen takes a different view of the subject, 

 when he states that "In the first and second dorsals the pleurapophysis (1 and 2) 

 terminate in a free pointed end, like the 'false floating ribs' of Anthropotomy; in 

 the third the pleurapophysis, plate 3, articulates with the haemapophysis h ; which, in 

 connection with its homotypes, constitutes the bone called ' sternum,' f." The letters 

 given refer to a cut showing the first three dorsal vertebrae and scapular arch of a 

 bird, in diagrammatic side view [Anat. Vert. 2:15]. I have found in Otocoris the 

 second pair of ribs free, they being connected with the sternum by haemapophyses in 

 another specimen of the same species, so that in this case some would claim them as 

 true dorsals, or as dorsals any way (Owen) ; while others could but say that the 

 number of pairs of dorsal ribs varied. This state of affairs in Otocoris is no more 

 an unusual occurrence than the occasional presence of cervical ribs in man [Owen, 

 Anat. Vert. 2: 298]. Now, among the Tetraonidae we found another condition that 

 proved equally interesting; with them there are, in the backbone in the dorsal region, 

 four vertebrae that in the adult completely fused together, and the pairs of ribs that 

 articulate with the anterior vertebra of this compound bone do not connect with the 

 sternum by haemapophyses. Here we must, if we consider the floating ribs in this 

 region as cervical ribs, consider that a cervical vertebra has become anchylosed with 



