60 Proceedings of the Royal Irish Academy. 



plate of the palate at the median suture is only three lines long, from 

 before backwards, while the right exceeds four lines. There is also a 

 trace of premaxillo-maxillary suture on this aspect. The ethmoidal 

 spine of the sphenoid is trefoil- shaped, with two alee minimse 

 (Luschka). There is a carotieo-clinoid canal on the right, but only a 

 stumpy middle clinoid process on the left. 



The right malar bone has an exceedingly long maxillary process 

 extending as far as over the canine tooth, and four lines internal to 

 the infra-orbital foramen. The root of the process is slightly concave 

 below, excavated for the orbital head of the levator labii superioris. 

 Its anterior end is separated from the outer hamulus of the lachrymal 

 bone by a slender isthmus of the margo -lachrymalis of the maxilla 0*7 

 of a line broad. This margin directly behind the tip of the malar has 

 a transverse suture and a small foramen. On this side there is no 

 sutura infra- orbitalis transversa, but the nasal process of the maxilla 

 has an oblique vascular groove. The malar is excluded on this as on 

 the left side from forming the anterior boundary of the spheno-maxil- 

 lary fissure, as there is a sphenoidal process of the maxilla. On the 

 left side the processus maxillaris is still more extensive, and stretches 

 over the whole infra-orbital edge of the maxilla ; crossing the margo- 

 lachrymalis to join internally the end of the crista lachrymalis, it 

 bridges over an imperfect sutura infra-orbitalis, and stretches in front 

 of the large external hamulus of the lachrymal bone, with which it 

 forms a suture of about a line and a half in length. The lachrymal 

 and malar thus form a complete belt, excluding the maxilla from 

 forming any part of the brim of the orbit. (Plate 1, fig. 1.) 



As will be seen from the Table, such an extreme case of inward 

 extension seems to be unique ; at least I know of no record of such a 

 condition. 



Turning to the comparative anatomy of the processus maxillaris, 

 we find that in the anthropoids the processus does not extend even as 

 far inwards as in man. In the Gorilla (3 skulls) the process falls short 

 of the infra-orbital foramen. In the Orang (1 skull) it falls still farther 

 short. In the Chimpanzee ( 1 adult and 5 young skulls) it also falls short. 

 In Hylobates Siamanga (1 sp.) it extends to the level of the foramen. In 

 Inuus, Cercopithecus, &c., it falls short considerably, or else stretches 

 nearly to the level. The only one of the Quadrumanous Primates 

 wherein I found a lachrymo-jugal suture present was a Rhesus, spe- 

 cies unknown, in which the large lachrymal bone forms the entire 

 circumference of the depression for the lachrymal sac, and the long 

 square malar sends in on each side a processus maxillaris to articulate 

 with the edge of the former. (Plate 1, fig. 2.) 



Among the Platyrrhines there is no trace of such a suture in Ce- 

 bus, Mycetes, Ateles, or Callithrix. The Marmosets (Hapale) have 

 the short wide processus maxillaris far from the lachrymal, and 

 among the Lemurs there is no union or lachrymo-jugal contact in 

 Tarsius, Lepilemur, Stenops or Lemur. 



Among Ohiroptera there is no lachrymo-jugal suture in any genus 



