The origin of the occipital condyles of the skulls of vertebrata has not so far been elucidated. They are separate elements from the occipital arch and are ultimately superimposed on the latter, except in fish. The occipital arch is the hinder limit of the skull; and the arch which is the beginning of the vertebral column may be termed the atlas, though it is not homologous in Amphibia and Amniota. Between the occipital region and the atlas there is an intervertebral body which acts as a buffer. An intercalated arch is present on the dorso-lateral sides of this intervertebral body, the existence of which was not previously known; this arch is not complete dorsally and does not enclose the spinal cord; the nerve, spinalis I., passes through or over this intercalated arch.
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Journal of Morphology (1939)