Morphology of the Human Lachrymal Bone., c. 247 



most macerated skulls, and seems to be quite absent in Otaria and 

 Cystophora. 



The Prosimii preserve the same type of bone, but in adult skulls 

 its early ankylosis with the maxilla renders it often difficult to 

 isolate. They have all well-marked lachrymo-jugal sutures with 

 lachrymo-maxillary sutures both in front and behind the malar. 

 Chiromys has a large premaxillo-lachrymal suture, but this I have 

 not noted in any other Lemuroid. 



Among the Primates, the two types of smaller lachrymal exist. It 

 is large, facial, and articulates with the nasal in Mycetes ; smaller 

 facial, and perforate in Ateles with a wide outreaching hamulus, 

 whose lower surface partly roofs in the infra-orbital canal. In Cebus 

 Pithecia, Callithrix, and JSyctipithecus it is imperf orate, but has a very 

 large hamulus, and the same form exists among the Arctopithecus. In 

 Callithrix, from the peculiar construction and absorption of the 

 interorbital septum, the back of the small lachrymal is bounded by a 

 fronto-maxillary suture, and the same exists in Nyctipithecus. 



The Catarrhines present several varieties of form ; the perforate 

 form with the continuous anterior margin is present in Cercopithecus 

 and Macacus, while the anterior bar is medially interrupted in Semno- 

 pithecus and Nasalis. Macacos nemestrinus alone has a lachrymo- 

 jugal suture, among the Catarrhines. The hamulus in all the cynoid 

 Catarrhines is very deep and wide, extending usually to the face and 

 spreading outwards far into the floor of the orbit. 



The Gorilla has a long upper angle ascending forward to the frontal, 

 and a short ethmoidal suture. As in all the other Catarrhines, the 

 lower end of the lachrymal process projects, shelf-like, forwards. In 

 five skulls I found a sutura notha and a sutura infraorbitalis 

 verticalis. 



The Orang has a long sharp hamulus, so placed that its edges look 

 . out and in, its surfaces up and down. The Chimpanzee has also a 

 small lachrymal with a wide hamulus. 



By following the lachrymal bone downwards among Vertebrates, 

 something of the stages whereby it has become specialised from the 

 inner elements of the suborbital ring of dermal ossicles, can be 

 traced. 



Among birds the bone occupies a position comparable with that in 

 mammals, is exceedingly variable in form, not pierced by the 

 lachrymal duct, and often attended with accessory ossicles, one 

 (falcons, &c.), two (puffins, &c.), three (Procellaria, &c.), or four 

 (Psophia). 



Among Reptiles the same inner region of the orbit is occupied by 

 two dermal ossicles, membraue-prefrontal and lachrymal, and occa- 

 sionally by small granular accessory ossicles as well. Among the Am- 

 phibians, in the skulls of some of the extinct Labyrinthodonts, such 



