82 Annals of the Carnegie Museum. 



far as it refers to the skulls of these animals belonging to the same 

 species. 



As will be seen in my figures, the orbital cavities in the skull of Aotus 

 miriquouina are circular and of great size, being hemispherical in form, 

 each in its entirety, with the margins sharp, except where they are 

 formed by the nasals and frontals. The vault of the cranium, super- 

 ficially, is smooth, and probably it wi'.l be found that the direction of 

 the lines of the sutures exhibits in different skulls as many variations 

 as we find among human skulls, as well as those of other anthropoids. 

 For example, in the skull figured by Elliot the coronal suture forms an 

 arc with the concavity forwards; in the skull at hand it forms an angle, 

 the sharp apex of which, directed backward, is met by the anterior 

 extremity of the sagittal suture. On the lateral aspect of this skull 

 it will be noted that the squamous portion of the temporal is small, 

 as is likewise the case with the alisphenoid. This allows the parietal 

 to make an extensive articulation with the malar of the same side, 

 while the alisphenoid is far removed from both the frontal and parietal 

 bone, articulating with the temporal and malar far down in the fossa 

 nearly opposite the zygoma. The aural apertures are circular in 

 outline, and the bullae conspicuously elevated with their osseous walls 

 inclined to be thin. These bulbous enlargements of the "petrous 

 portion" of either temporal bone are entirely absent in such an ape as 

 Lasiopyga callitrichns. The occiput is especially prominent, and there 

 are two marked concavities between it and the foramen magnum, 

 placed side by side, transversely. 



The form of the mandible in Aotus is well shown in the figures on the 

 plates, and it is to be noted that the ramal walls are thin, while the 

 symphysial is thick and strong. The "sigmoid notch" between the 

 coronoid process and condyle is narrow and semi-circular in outline, 

 the process rising considerably above the condyle. 



The hyoidean apparatus in this specimen has been lost, and so 

 has the atlas vertebra. 



In the "spinal column" we find seven cervicals; twelve dorsals; 

 nine lumbars; three sacrals and twenty-five caudals. There are 

 thirteen pairs of ribs, nine pairs of which join with the sternum 

 through costal ribs. An abnormality is seen here in the elongation of 

 the pleui apophysis of the second lumbar vertebra on the left side, 

 articulating with the extremity of which theie is a small, free rib, 

 some seven mm. in length. 



