| OCR Text |
Show 1901.] SKULLS OJT LEMTJKS ANT) MONKKYS. 131 p. 136), Galago (text-figs. 34, 36, 38, 39, pp. 138, 139), possess a large os planum, which very often is not even limited to the orbit; it seems to have been overlooked because in older individuals the sutures within the orbit disappear, as indeed is the case with almost all the cranial sutures. Amongst the Malagasy Lemurs a fairly large os planum is present in all the species of Microcebus. In the other genera the planum becomes fused with the palatal at a very early date (text-figs. 28 & 37). A distinct small os planum is often visible in young specimens of Hapalolemur, Chirogale, Lepidolemur, and Avahis (text-fig. 27), and sometimes in Lemur. Chiromys is the only Lemur in which I have not been able to trace the planum (text-fig. 26). Text-fig. 20. mcc. vn-S Orbital region of Chiromys madagascariensis. Nat. size. ma.ins. = insertion of the malar on the maxillary; ma. = malar ; mx. = maxilla ; I. = lacrymal; pi. = planum ; as. = alisphenoid ; os. = orbito-sphenoid; fr. =frontal; ^>a.=palatal ; ,r. = intercalar bone; ,«.=intercalar bone. In a general manner we can state that in those Lemuridse which are provided with a large lacrymal, the os planum is reduced ; vice versa the lacrymal is reduced or absent-at least from the orbit and the outer surface of the cranium-in those Lemurs which are provided with a large os plauum. Further particulars with regard to this bone will therefore more suitably find their place in connection with the description of the lacrymal. Sketches of the os planum in various Lemurids are given in the text- 9* |
