| OCR Text |
Show 1900.] STRUCTURE OF THE MUSK-OX. 697 answer must be the first, or Antilopine, in fact tbe primitive one. The fronto-parietal region forms a perfect plane without tbe slightest trace of " Knickung," and the parietals are fully developed and partake in the roofing of the brain-case. It is accordingly quite evident that this part of the skull of the Musk-ox shows no affinity either with the Oxen or with the Sheep, but is of the more primitive Antilopine type l. The origin of the horn-cores in Ovibos is different from that of the Antelopes, as it is perfectly lateral. In the skull of a young Musk-calf shot by Professor Nathorst on the 26th of August, and thus probably about three months old, the beginning of the horn-core appears as a small tubercle situated about 4 cm. behind the orbit, and about 1 cm. from the sutura coronalis2. The born-core thus originates only on the frontal bone, but its base expands gradually with age in a median as well as backward direction, so that in an old bull, as is well known, it covers not only the posterior portion of the frontal, but also the whole parietal as far as the sutura lambdoidea. In this way the same effect is produced in Ovibos as in the Ovina and Bovina, viz., the horns get their insertion on to the vertex of the skull. The Fig. 5. Section of skull of Musk-ox. result is, however, obtained by quite different means in the three types, and the vertex is not situated in the same cranial region. It must also be remembered that the Musk-ox ontogenetically and gradually passes through all intermediate stages of its development from the primitive one ; but this is not the case in the others. 1 The fronto-parietal and the occipital planes form a right angle with each other, and the highest point of the Musk-ox skull is therefore at the sutura lambdoidea. 2 There is a more pronounced tubercle situated at the edge between the upper and lateral surfaces of the skull, and divided by the sutura coronalis. This cannot, however, be the origin of the horn-core, as it becomes evident from Sir John Richardson's figure that the horn-core in a 16 months old animal is still situated only on the frontal bone. |
