On the archetype and homologies of the vertebrate skeleton / by Richard Owen.
- Richard Owen
- Date:
- 1848
Licence: Public Domain Mark
Credit: On the archetype and homologies of the vertebrate skeleton / by Richard Owen. Source: Wellcome Collection.
Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.
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![only the nerve-trunks to be protected by the nasal neurapophyses. T1 are, therefore, more approximated, and the anterior termination of the ne canal is much contracted ; and, in the tailless batrachia, the nasal n< apophyses coalesce together. We recognise in that element (20) of the fourth or foremost inverted of the crocodile’s skull, which is in connection with the body (vomer, 13) descending plates of the neurapophyses (prefrontals, 14) of the nasal verte the proximal oxpleurapophysial element of such arch; and the same n tition of the characteristic connections of the bone, 20, which enabled Cu and Geoffroy to recognise its special homology with the palatine bone in fish, establishes its claim to be equally regarded in the crocodile as the ph apophysis of its vertebral segment; although it now affords but a partial tachment to the bone 21, which forms the next element of the inverted ai This bone, the hcBmapophysis, has undergone a striking change in its proj tions by development both in length and breadth; it is connected not only v> no. 20 behind and with no. 22 before, but with the elongated spine, no. is, ol^ own vertebra, and with the lacrymals, 73, above ; with its fellow of the oppo side below, and with a well-developed proximal element, no. 20, of a stn diverging appendage behind. The Immal spine, no. 22, is divided, and arch is completed by the symphysial junction of the two halves at H iv. nasal aperture or entry to the air-passages forms the span or area of much-modified inverted arch constituting the upper jaw of the crocoo The two proximal elements of the arch, nos. 20 and 21, continue to st- outwards and backwards exogenous diverging processes ; but they con tute a smaller proportion of the bones than in fishes, and both processes- rectly support distinct bones representing the diverging appendage of arch, and serving to fix and attach it to the succeeding arch. The pleura physial appendage (pterygoid, 24) soon coalesces, however, with its fell and with the centrum of its own vertebra (vomer, 13), and then expands unite by a broad sutural surface with the coalesced centrums of the fror and parietal vertebrae (a and 5). A second osseous piece (ectopterygci 24') diverges from the pleurapophysis external to the preceding and attach it to the haemapophysis, to the haemapophysial appendage, and to the p: apophysis of the frontal vertebra. The strong diverging ray from the hast apophysis is teleologically subdivided into nos. 20 (malar) and 27 (squamosa and firmly attaches the maxillary arch to the pleurapophysis (23) of the m; dibular one. In the chelonian reptiles the modifications of the nasal segment of 1 skull adhere pretty closely to the type of those in the crocodile ; the centrr is more independent and better developed, but the divisions of the neu spine have coalesced with their neurapophyses; the diverging appendag. 20 and 27, are usually developed into broad and flat bones. In many lizar we find the nasal centrum divided but the neural spine single: the hajR spine is, also, single, as a general rule, and sends upwards and backward^ process to join the neural spine, divide the area of the haemal canal, aj terminate the vertebral series anteriorly. The haemapophysial diverging £| pendage commonly resumes its long and slender ray-like proportions, and joi; the parapophyses of both frontal and parietal vertebrae as well as the prc] imal end of the pleurapophysis of the mandibular arch. In serpents bo! divisions of this appendage are absent (indicating the inferior character the bones 20 and 27 in general homology), but the two parts of the pleurapi physial appendage, 24 and 24', are retained and serve as levers in the raovjj nients of the maxillary arch. The spine of that haemal arch is single, ai 1 commonly united only by lax and elastic ligaments with the haemapophysi®](https://iiif.wellcomecollection.org/image/b21307830_0136.jp2/full/800%2C/0/default.jpg)
