OCR Text |
Show 248 MR. G. E. DOBSON ON CAPROMYS MELANURUS. [Apr. 1, The liver (Plates XIX. and X X . figs. 1, 1 a) differs from that of G. pilorides (Plates XIX. and X X . figs. 2, 2 a) chiefly in the absence of that subdivision of the lobes into lobelets, as originally described by Say and subsequently by Owen in that species, and as shown in the figures above referred to. The primary division of the liver of C. pilorides into lobes is, however, on precisely the same plan as in G. melanurus, as may be seen by comparing the figures, the principal difference in the general outline being noticeable in the right and left central lobes, which in C. melanurus scarcely exceed the right and left lateral lobes in length, but in C. pilorides are greatly produced backward. In both species the Spigelian lobe (s) is small and similarly shaped, and in both there is a similar separated portion (11) of the left lateral lobe (l.l). The gall-bladder is well-developed'. The other abdominal viscera are as in C. pilorides. The epiglottis is short, and rounded at the tip. The vocal cords are shallow, but very dense in structure, with sharply defined margins, as in G. pilorides, but there are no distinct sacculi laryngis. With this exception Prof. Owen's description of the larynx of C. pilorides also applies to this species. The trachea is formed of twenty-eight cartilaginous rings, dorsally imperfect; the bronchi diverge gradually, and the right bronchus much exceeds the left in calibre. The lungs are divided into lobes precisely as in C. pilorides. The heart is rounded at the apex, without trace of a notch between the ventricles. As in G. pilorides and Erethizon dorsatus 2, there is a large innominate artery which gives off the right subclavian and the two common carotid arteries, the left subclavian arising separately from the arch of the aorta. The arrangement of the precaval veins differs, however, remarkably from that of G. pilorides as described by Prof. Owen, for instead of the blood returned from the head and anterior extremities being emptied into the right auricle by a single vein, there are, as in most species of Rodentia and Insectivora, two precaval veins ; the left precaval vein receives the left vena azygos and winds round the heart to open into the right auricle, while between the orifices of the right and left precavals the postcaval vein enters. The male generative organs cannot be described for want of material, but they probably resemble those of C. pilorides described by Prof. Owen (/. c ). The clitoris is provided with a long prepuce, and is perforated by the urethra; the vagina is remarkably long and spacious, and its walls are marked by numerous rugosities. The uterus (Plate XXI. fig. 4) is bicomuate ; the long cornua unite by their internal margins in their posterior thirds, but their cavities continue separate almost to the vagina, into which, however, they open by a single os. The ovaries, as in the Hare, are not enclosed in peritoneal capsules, each capsule is quite open, and the Fallopian tube, after pursuing a tortuous So differing from Erethizon and Cercolabes, where there is no trace of one. It must, however, be remembered that there is a gall-bladder in the closely allied Hystrix. 2 Mivart, P. Z. S. 1882, p. 279. |