1867-] MR. ST. GEORGE MIVART ON INDRIS DIADEMA. 255 



by the three forms (which I consider to,2;ether constitute but a single 

 genus) may perhaps be expressed as follows : — 



Indrisin.^;. Indrts. 

 I.^. C.;e|. P.M.g. M.fE^ = 1^ = 30. 



Characters. — Ears short; muzzle moderate, or rather or very 

 short ; hind legs much longer than the fore limbs ; index very short, 

 much shorter than the fifth digit ; poUex short and placed far back ; 

 hallux very long and covered with hair ; tail long, or very short and 

 rudimentary ; internal condyle of the humerus perforated ; carpus 

 destitute of an os intermedium ; tarsus short ; first upper molar with 

 four principal cusps, and from two to four supplementary ones ; last 

 upper molar with only two well-developed cusps ; each lower incisor 

 with its outer surface longitudinally grooved ; posterior lower pre- 

 molar much antero-posteriorl}^ extended ; first lower molar with five 

 more or less distinct cusps ; last lower molar quinquecuspid ; a pa- 

 ramastoid process ; no malar foramen ; lachrymal foramen very near 

 the margin of the orbit ; a process depending from zygoma in front 

 of, and external to, the glenoid surface ; a glenoid foramen ; ante- 

 rior palatine foramina very large ; mandibular symphysis very long ; 

 condyle rounded, but very little transversely extended ; articular 

 surface prolonged somewhat down the back of ascending ramus ; 

 digastric fossa more or less deep. 



Hab. Madagascar exclusively. 



Indris brevicaudatus. 



Characters. — Ears exserted ; muzzle moderatelv long ; tail short; 

 posterior pair of upper incisors not much larger, sometimes decidedly 

 smaller, than anterior pair ; upper canine longer than first premolar; 

 skull not concave between the orbits ; antero- posterior extent of the 

 anterior opening of the orbit less than the length of the muzzle in 

 front of that opening ; no protuberance above the external auditory 

 meatus ; no process of the malar projecting over the anterior end of 

 the zygomatic process of the squamosal ; floor of orbit considerably 

 above the upper alveolar margin ; a large palatine foramen behind 

 the third molar ; palate with its posterior margin thickened ; man- 

 dibular symphysis much less than three times the length of the 

 lower incisors ; fossa for digastric not very deep ; posterior part of 

 articular surface of condyle not grooved, nor always much flattened ; 

 angle very much bent downwards, making the inferior margin of the 

 mandible exceedingly concave. 



Hab. Madagascar, but not St. Mary's Island. 



Indris diadema. 



Characters. — Ears short, in the fur ; muzzle rather short ; tail 

 long ; posterior pair of upper incisors much smaller than the ante- 

 rior pair ; upper canine larger than first premolar ; last upper molar 

 very small ; skull not concave between the orbits ; antero-posterior 



