OCR Text |
Show 1879.] MR. W. A. FORBES ON THE GENUS LATHAMUS. 173 made; and till that is done it is perhaps somewhat premature to generalize. Nevertheless, having examined somewhat carefully a considerable number of the skeletons of the two groups with which Lathamus has been generally associated, I have, I believe, been able to detect certain differences which will help us in referring the bird at present under discussion to its proper place. First, as regards the skull. This, in all the Trichoglossince, is remarkable for its somewhat depressed form and the lateral compression and elongation of the upper and lower jaws, the mandible when deprived of its horny sheatb showing even more clearly the peculiar shape of the lower jaw in these birds, first pointed out by Sundevall and already alluded to above (PI. XVI. fig. 7). In the Platyctrci the skull is less depressed above and much shorter in proportion, and the mandible is not pointed, but has its symphysial portion wide, deep from above downwards and somewhat truncated. The same is the case in Lathamus (PI. XVI. fig. 8). In the Lories the lengthening of the beak has led to a similar elongation in the anterior limb of the palatine bones, so that this part is as long as, or longer than, the posterior one ; and the latter is considerably shorter than the pterygoids. In the Platycerci the anterior part of the palatines is not so elongated ; but, on the contrary, the posterior limb is somewhat lengthened, and, in fact, nearly as long as the pterygoids. Here, again, Lathamus agrees more with I he Platycerci. In the Lories (PI. X V I . fig. 9, Eos rubra) the anteorbital processes are much larger and better-developed than in the Platycerci, where the hinder margin of these parts, as seen from above, is not very far from being on a level with the cranio-rostral suture, and so causes the orbits to take up a larger part of the surface of the skull (in a view from above) than in the other group. The same is the case in Lathamus1 (PI. XVI. fig. 10). The retention of the furcula is no doubt associated with the rapidity of flight of this bird, whilst in the more slowly moving Platycerci it has disappeared almost entirely. As we already know from M. Blanchard's researches (Ann. Sci. Nat. Zool. xi. pp. 84-85, 1859), but little assistance as regards classification can be gained in this group from a study of the sternum. The pelvis, however, has been of more use to me. In the Lories this is always elongated and narrow in proportion, the preacetabular part being particularly elongated, and the iliac fossae on each side for the attachment of the gluteal muscles being deeper and more extensive. In the Platycerci and Lathamus the 1 Bonaparte (Compt. Bend. xliv. p. 536, 1857), following Owen (Cat. Osteol. Series B. C. S. 1853, p. 279, no. 1451), says that in Lathamus the orbit is completed below by the junction of the lacrymal with the " mastoid." This is certainly not the case in a skull lent to m e by Professor Garrod, and, if true, would be an anomaly for any member of either of the above-mentioned groups. In the specimen referred to in the Museum of the College of Surgeons (no. 1451) it appeared to m e on examination that there was in reality no bony union between the two bones, which were connected simply by ligament. |