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Show 1901.] SKULLS OF LEMURS AND MONKEYS. 135 The posterior portion of the lacrymal descends to a considerable extent into the orbit, forming a very open angle with the anterior portion-the homologue of the sulcus lacrymalis-which runs forward almost horizontally. But there is no crest (cristaposterior I.) dividing the two portions; and the blunt crista anterior is exclusively formed by the maxilla, which delimits the lacrymal fossa in front, and at the same time forms the lower anterior margin of the orbit. The lacrymal fossa, therefore, is situated entirely inside the orbit. The malar bone, which laterally continues the lower orbital margin, proceeds farther medially than in M a n and generally in. Monkeys, without, however, reaching the lacrymal, from which it is separated by a process of the maxillary projecting laterally into the fossa. Medially, a similar process of the frontal enters also the fossa from behind, the lacrymal (the anterior part of which is broken in the specimen) being thus situated between the two processes. P. Gervais, to w h o m we owe one of the earliest descriptions of the skull of Adapis jwm/exsi's (" Palosolemur")l, mentions as one of the Lemurine features of the skull " la position infero-externe du trou lacrymal et son developpement." In his figure 3 (pi. xvii.) are in fact represented two foramina situated on the facial part of the cranium and occupying approximately the position of the fossa lacrymalis in many recent Lemurs. The comparison of Gervais's figure with the skull in the British M u s e um (No. M 1345) shows, however, that these supposed lacrymal foramina are not foramiua at all, but deep circumscribed depressions of the maxillary, in front of crista anterior, which exhibit the appearance of foramina when the shade falls into the hollow. In a subsequent publication by Gervais'2, either the author or the artist seems to have become aware of this fact, for the two supposed foramina are entirely omitted from the figure representing the very same cranium ; the description is, however, reprinted :i without alteration from the ' Journal.' The skulls of Adapis magnus in the Geological Department show the cranial region which interests us here, in a broken condition, and in the same case are unfortunately the skulls of Microclicerus (Necrolemur). For the present, therefore, the oldest Lemurid exhibiting the lacrymal region shows it to be conformed exactly the inverse of what might have been anticipated and in fact has been supposed to be the case. Since Adapis parisiensis agrees iu several important features with recent, and most of all with the Malagasy, Lemurs4 , it may be fairly taken to be in their ancestral line. The condition of the lacrymal region in recent Lemuridae is easily derivable from that obtaining in A. parisiensis, in supposing that by the flattening of the maxilla's crista anterior and the upraising of a crista 1 Journ. de Zool. ii. p. 422, pi. xvii. (1873). 2 Zool. et Pal. gen. ii. pi. viii. fig. 2 a (1876). 3 Op. cit. p. 32. * P. Z. S. 1899, p. 988. |