1901.] SKULLS OP LEMURS AKB MOTS'KETS. 133 



fossa is not yet situated within the orbit." In Ateles the laciymal 

 forms the greater part of the border of the fossa — including the 

 upper half of the erista anterior and its antero-superior angle — and 

 projects towards the uasal, so that there is only a narrow suture 

 between the frontal and the frontal process of the maxillary. 



In Mycetes the lacrymal projects farther still, uniting with 

 the nasal; besides, the whole of the fossa is encircled by the 

 very large lacrymal, " a position which most approaches to that of 

 Lemurs." 



In Nyctipithecus {N. trivirgatus), the third platyrhine genus 

 mentioned, the whole of the crista anterior is formed by the 

 maxilla, thus presenting a condition more closely approaching 

 the Simiidae and Man than even in the Cercopithecidse. Nycti- 

 plthecus recalls Mycetes and Ateles only in the projecting of the 

 antero-superior lacrymal portion, which separates almost com- 

 pletely the maxillary from the frontal. 



In the Cercopithecidfe (" Semnojnthecits, Tnims, Cereopitlieem, 

 Cercocehis, Cynocephalus '"), although the position of the lacrymal 

 fossa is undoubtedly orbital, it is almost entirely encircled by the 

 lacrymal bone, the crista anterior being either entirely formed by 

 the latter bone, or by the lacrymal together with the frontal 

 process of the maxillary. All the Cercopithecidae exhibit an 

 enlargement of that part of the lacrymal (the hamulus of Human 

 anatomy) which borders the fossa laterally, so that we find 

 here an extensive plane. Various individual variations are men- 

 tioned, to which will be referred further on. G-egenbaur sums 

 up in the following words : — " Das von Befunden an Thieren 

 Angef iihrte geniigt, um zu zeigen, dass dem Lacrymale in niederen 

 Zustiiuden eine faciale Ausdehnung zukommt, und dass die Pars 

 facialis in den hoheren Abtheilungen Rlickbildungen erleidet, 

 wodurch die Pars orbitalis zur ausschliesslichen Repriisentanz 

 gelangt. In dem Maasse als diese Eiickbildung stattfindet und 

 dadurch die vordere Umgrenzung des Canalis lacrymalis vom 

 Thranenbein aufgegeben wird, tritt der Stirnfortsatz des Ober- 

 kiefers daflir ein, und gelangt vorn zur Umschliessung jener 

 Grube. Das ist beim Menschen wie bei anthropoiden Affen 

 zur Kegel gewordeu : der Hamulus ist der Rest der Verbindungs- 

 strecke von Pars orbitalis und P. facialis . . ." ^ 



It is necessary to insist upon two results of this investigation : 

 (I) the curious circumstance that, whilst of the three platyrhine 

 genera mentioned, two represent the lowest stage in Monkeys, 

 the third one on the contrary represents the highest, if we except 

 the SimiidsB. And (2) that the encircling of the whole of the 

 lacrymal fossa by the largely developed facial portion of the 

 lacrymal — occurring in the Lemurs and in Mycetes — is considered 

 to be the lowest condition, from M'hich the condition in higher 

 forms is said to be derived by a gradual reduction of the i^ars 

 facialis, the reduction being initiated by the maxillary replacing 

 the lacrymal in front of the fossa. 



1 Op. cit. p. 176. 



