PEIMATES TEOM MADAaASOAE. 79 



orbit agree in general with the corresponding bones in Propithecus. The following 

 deviations from the type of the recent Indrisinse may be noted. The lacrymal enters 

 to a very limited extent into the face, but has a considerable downward extension 

 within the orbit, resembling the condition seen in some of the Hapalidse and Cebidte (see 

 text-fig. 48, p. 152). It has at the same time a very considerable extension in a direction 

 in line with the orbital rim. The inner edge of the orbital rim shows an extraordinarily 

 developed elevation, forming in some old specimens a roughened prominence 5 mm. 

 high and 10 mm. or more in length. The lacrymal fossa is entirely surrounded by the 

 lacrymal bone, and in most specimens the foramen is well within the orbital margin. 

 In the youngest skulls which I have been able to examine the foramen is in line 

 with the sharp inner edge of the orbital margin, and, strictly speaking, this condition 

 generally still obtains in the adult, though the great forward and upward development 

 of the orbital rim as adult age is reached leaves the whole fossa well within the orbit. 



The small size and elevated position of the orbits on the one hand and the constricted 

 postorbital region on the other, naturally alter the contours of the maxillary and frontal 

 bones in this part of the skull. In Indris the posterior part of the maxilla is inflated 

 by an extensive aerial sinus and forms a veritable floor for the eyeball. In Falmo- 

 propithecus the maxilla rises up to form an extensive fronto-maxillary suture between 

 the lacrymal and the ethmoid, but forms no horizontal floor as in the extant genera. 

 The ethmoid has been mentioned as entering the orbit in Palwopropithecus. There is 

 apparently in young skulls in the position where this bone occurs in Propithecus (viz., 

 at the point where the frontal, maxilla, orbito-sphenoid and palatine all approach each 

 other) a small os planum which early fuses with the end of the palatine, and in older 

 animals is drawn in away from the orbital wall by the sinking in of the margins of the 

 spheno-palatine and postpalatine foramina. 



The great depth of the malar below the orbit has been referred to. Below and 

 within the outer orbital margin this bone is triangular in section, presenting a distinct 

 inner ridge which partially walls in the orbit behind. A downwardly extending ridce 

 of the frontal serves a similar purpose in the upper part of the orbit. We shall have 

 occasion in succeeding sections to notice a similar condition of the postorbital bar in 

 several of the other subfossil Malagasy Lemuroids. 



The Nasal Begion. — The nasals are broad and flattened as compared with those of 

 the modern genera. Their median suture is early obliterated, as also are those they make 

 with the frontal and maxilla, but their contour can be readily traced on a young skull. 

 Each nasal sends out a rounded wing to meet the anterior angle of the lacrymal. The 

 nasalia are slightly constricted in the front of this point, the two edges runnino- 

 parallel for a short distance, when they again broaden out, resembling closely the 

 corresponding part in Archceolemur. At their anterior end the nasals are curiously 

 turned up, and along their outer anterior margin form a suture with an upwardly 



