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Show 1894.] ANATOMY OF ATHERURA AFRICANA. 677 In A. africana the suture between the malar bone and the maxilla is much further forward than in A. macrura, its distance from the nearest point of* the great infraorbital foramen being from l to | in., Avhile in A. macrura it is considerably over | in. Another point worthy of notice is that in 4 out of 6 skulls of A. africana an os antiepilepticum or "Wormian bone at the junction of the*coronal and sagittal sutures was present. In four skulls of A. macrura it was not seen once1. The cervical vertebrae are remarkable for the large and recunred spine of tbe atlas. The sixth shows a large ventral tubercle on the transverse process corresponding to the carotid tubercle of human anatomy. In the seventh this tubercle is suppressed. The thoracic vertebrae are 14 in number, the anticlinal being the 13th. The transverse processes gradually broaden and tend to bifurcate until at the 8th there is a fairly distinct metapophysis projecting from the anterior part and an anapophysis from the posterior. The lumbar vertebrae (fig. 2, p. 678) are 5. The anapophyses are well marked until the last one, where they disappear2. Ventral to the disc between the first and second vertebrae are f\vo ossific nodules about the size of pins' heads, which apparently are serially homologous with the chevron-bones in the caudal region, and probably correspond to the intercentral in the Mole, although 1 believe that these structures have not yet been described in Bodents. In another specimen which I examined I found these nodules between the 2nd and 3rd, 3rd and 4th, and 5th and 1st sacral3. The sacral vertebrae are sometimes three, sometimes four. All the costal processes are completely fused into a horizontal plate, while the spines are only slightly fused. In the structure of the sacrum Atherura agrees with Hystrix and differs considerably from the Tree-Porcupines. There are 24 caudal vertebrae, the first four of which have projections from the ventral surfaces of the costal processes. Between the last sacral and first caudal vertebrae chevron-bones are seen as small nodules. Between the first and second caudals there is a small haemal arch ending ventrally in a point; beyond this the haemal spines broaden out anteriorly but are compressed laterally ; there are altogether 16 of them. The sternum consists in one case of five and in another of six sternebrae. In front of the anterior one there is a leaf-shaped cartilage. Tbe anterior sternebra or manubrium is remarkable in the animal I dissected in that the first and second costal cartilages 1 W. Gruber in 'Memoires de PAcad6mie de St. Petersbourg,' xix. no. 9, describes the presence of this bone in several Rodents, but not in Porcupines. 2 In another specimen they were absent in the last two. 3 The occurrence of these paired intercentra is interesting when compared with a paper by Boulenger, P. Z. S. 1891, pp. 114 & 170. In it he points out that, in Lizards, the intercentra or hypapophyses may be either paired or median. - •'•"'! |
