152 ON THE SKULLS OP LEMUBS AND MONKEYS. [I'eb. 19, 



the Lemurs, as well as in the Monkeys, not a primitive condition, 

 but an extreme specialization. 



The postorbital region, to which the figures of Plate XIII. refer, 

 has been examined in about 1100 skulls of Monkeys (exclusive of 

 the Anthropoids, except Eyhhates) and 300 of Lemurs ; so that 

 the ten figures are only just sufl3cient to give a general idea of 

 the gradual changes. For all the particulars the reader is referred 

 to a separate publication. In the characters of this region the 

 Lemurs do not stand apart as has been supposed (Virchow) ; they 

 represent the most generalized condition, closely related to what 

 obtains in the majority of the platyrhine Monkeys. From the 

 Lemurs to the higher Monkeys takes place a gradual restriction 

 and throwing back of the parietal, brought about by the greater 

 extension, first of the malar, and subsequently of the frontal, alis- 

 henoid, and squamosal. Phases in this whole process of evolution 

 are the differences between the Platyrhinae and Catarhinse (dis- 

 cussed by Cuvier, Joseph, Anutschin, W. A. Porbes), and the union 

 of the squamosal with the frontal ; the latter being the terminal 

 stage. As regards Man, the fronto-squamosal union is not an 

 atavism ; where it occurs it is — apa.rt from pathological cases — a 

 specialization, just as in Monkeys. "What has rather the appear- 

 ance of an atavism is the spheno-parietal union when it occurs in 

 the Gorilla and the Chimpanzee. 



EXPLANATION OP THE PLATES. 

 Plate XI. 

 Lacrymal region of Lemurs and Monkeys. 

 Z.=lacrymal; mx = maxillary ; ma. = malar ; ^/. = planum ; cr.a.mx. = crista. 

 anterior of the maxillary ; cr.^.^. =: crista posterior (of the lacrymal). 

 Fig. 1. Nesopithecus australis Maj. (Br. M. Geol. Dep.). 



2. Nesopithecus roberti Maj. (Br. M. Geol. Dep.). 



3. Mycetes imlliatus, young (Br. M. Z. D. No. 96.6.1.1). 



4. Fropithecus edwardsi, young (Br. M. No. 75.1.29.6). 



5. Cercopiihecus albogularis S (Br. M. No. 92.10.18.9). 



6. Mycetes palliatus (Br. M. Salvin's Coll.). 



7. Chrysothrix sciureus (Br. M. No. 45.8.5.8). 



8. Ehinointhecus roxellanm § (Br. M. No. 99.3.1.2). 



9. Papio anubis (Br. M. No. 45.6.17.14). 

 10. Papio sp. inc. (Br. M. No. 0.1.3.2). 



Plate XII. 



Lacrymal region of Monkeys. 

 Fig. 1. Brachyteles arachnoides (Br. M. No. 43.10.12.2). 



2. Midas geoffroyi $ (Br. M. No. 0.5.1.63). 



3. Colohus caudatus cj" (Br. M. No. 0.2.1.1). 



4. Ateles fusciceps (Br. M. No. 1514 a). 



5. Midas nvfiventer (Br. M. No. 54 a). 



6. Ateles vellerosus 2 (Br. M. No. 89.12.7.2). 



7. Callithrix personata (Br. M. No. 45.4.2.11). 



8. Semnopithecus natuncB, (^ type (Br. M. No. 94.9.28.1). 

 -9. Miopithecus talapoin (^ (Br. M. No. 0.2.5.8). 



10. Macacus rhesus (Br. M. No. 58.6.24.144). 



11. Nasalis nasicus (Br. M. No. 13 e). 



12. Macacus nemestrimcs (Br. M. No. 28 c). 



