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Show 120 MR. C. W. ANDREWS ON REMAINS OP MPYORNIS [Feb. 6, Of the two fairly complete large dorsals the one (Plate X V . figs. 5 & 6) which appears to be the anterior gives the following measurements:- • - cm. Length of centrum 7-5 Approximate height from ventral surface to top of neural spine 22*0 Width of centrum in middle 5*0 Diameter of neural canal from side to side 1*5 The centrum, which is slightly compressed, is produced ventrally into a hasmapophysis, which has been mostly broken away. The anterior articular surface is broader than high, while the reverse is the case in the hinder. The neural arch is very massive, and its sides below and in front of the broken transverse process are excavated by a large fossa roughly pyramidal in form. The articular surface of the anterior zygapophyses is nearly circular, its diameter being about 4-2 cm.; in the posterior the surface is oval. The neural spine which slopes forward is very large and high; it is united with the post-zygapophyses and transverse processes by two pairs of thin vertical buttresses of bone, and with the anterior border of the arch by a median unpaired buttress ; between these plates of bone there are deep pyramidal fossas. The result of this arrangement is that, though the vertebras are very large, they are at the same time extremely light. The transverse processes and the anterior lateral borders of the centrum being broken away, there is no trace of the articular surface for the ribs. The other large dorsal appears to have been posterior to the one just described. Its centrum is less compressed than that of the latter, and, as far as can be seen, there was no hasmapophysis. Both the anterior and posterior articular surfaces of the centrum are about as broad as high. The articular surface of the post-zygapophyses are ovoid in shape and of great size, the long axis of that on the left side measuring 6*7 cm., though in this specimen that on the right side is somewhat smaller. The fossas in the side and on the dorsal surface of the arch are much like those described above, but there is an additional median one between the post-zygapophyses, bounded in front by the neural spine and behind by the hinder border of the neural arch. The dimensions are :- cm. Length of centrum 7*2 Width of centrum in middle 6*0 Height of centrum in middle 6-0 As in the last specimen the articular facets for the ribs are broken away. As was mentioned above, the smaller dorsals closely resemble the larger in most respects ; they differ, however, in the form of the anterior and posterior articular surfaces of the centrum. These are concave and convex from side to side respectively, as |
