On the auditory ossicles of Rhytina stelleri / by Alban Doran ; (communicated by W.H. Flower).

  • Doran, Alban H. G. (Alban Henry Griffiths), 1849-1927.
Date:
[1883]
Catalogue details

Licence: Public Domain Mark

Credit: On the auditory ossicles of Rhytina stelleri / by Alban Doran ; (communicated by W.H. Flower). Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the malleus of Rhytina. The ‘ Vega- ’ specimen, being the more perfect, has been selected for this purpose. Antero-posterior measurement of 1 malleus (root of manubrium to > root of processus gracilis).... 1 Measurement from manubrium ) to most internal part of body > of malleus ) Length of manubrium ] Rhytina centim. 1-8 Manatus 1-8 Halicore IT Rhytina 2-5 Manatus 1-8 Halicore 1-3 Rhytina 2 7 Manatus 1-8* Halicore 15 The incus, both in the ‘ Yega ’ and the American specimen, is very similar to the same bone in Manatus. The body is shallow and wide between the crura. There is not the prominence behind the upper and more posterior of the two lower facets so conspi- cuous in Halicore ; so that the posterior part of the body is not larger than in the otherwise much smaller incus of Halicore. The upper facet is wider and deeper than in Manatus, but, as far as I could judge (not being able to disarticulate the bone from the malleus), of much the same shape. Its dimensions were as fol- lows :— Distance betwen Depth of body to extremities of point of crura. proc. brev. Rhytina 2'4 15 Manatus 1'6 l-2 Halicore 1'6 10 (As it is difficult to fix a precise “root” to the processus brevis, the “depth” is taken from the highest part of the body to the extremity —that is, to the point of ankylosis—of that process.) Lastly, in the American specimen the stapes existed. It fell out of its place in examination, which proved convenient, as will be seen; moreover it was readily replaced. In shape it is very similar to the stapes of Manatus seneyalensis. The head is equally well developed, and bears an almost circular articular surface 05 centim. in diameter (0‘4 centim. in Manatus). As in Manatus, also, both crura are long and hardly divergent; both also are crooked ; the anterior, too, iB the straighter, and is much thinner in proportion to the posterior than even in Manatus. The posterior crus is very bulky, and bulges higher up than in Manatus ; the thickuess of this crus encroaches upon the aperture, which is therefore much smaller proportionately than in the * The greater curving of the manubrium in this Sirenian, compared with Rhytina, must be taken into account, as the extremities are thereby approxi- mated.