SUBORDER A PROSIMIA 267 



Suborder A. PROSIMIA (LEMUROIDEA). Lemurs. 



Plantigrade, usually pentadadyl, frugivorous or omnivorous arboreal quadrupeds, 

 with opposable hallux. All digits have nails except digit II. of the manus. Denti- 

 tion frequently complete. Superior molars bunolophodont, quadritubercular, or tri- 

 tubercidar. Premolars less complex than molars. Inferior molars quadritubercular 

 or quinquetubercidar. Nasal bodies and muzzle elongated. Orbits posteriorly limited 

 by bone, but not separated by a wall from the temporal fossa. Lachrymal foramen 

 lying outside the orbit. Brain slightly convoluted, the cerebellum not covered by the 

 cerebral hemispheres. Mammae pectoral or abdominal. 



The lemurs are inhabitants of Madagascar especially, but are likewise 

 found in tropical Africa and southern Asia. They are distinguished from the 

 true apes by the smaller, less convoluted brain, by the large orbit posteriorly 

 limited by a bony bar but not by a wall of the temporal fossa, by the lachrymal 

 foramen lying outside the orbit, by the partially clawed digits, by the oppos- 

 able inner digit on the manus and pes, which is always well develojDed, by the 

 hairy covering of the face, the bicornuate uterus, and usually abdominal 

 mammae. The placenta is diffuse or bell-shaped ; a decidua is absent. 



In many respects the skeleton of the lemur is more primitive than that 

 of the apes, and recalls that of the Insectivora, Creodontia and modern 

 Carnivora. The hind -limbs are always longer than those in front, co-ossi- 

 fication never occurs in the carpus and tarsus, and as a rule a centrale 

 is present in the former. Calcaneum and naviculare are frequently 

 elongated. The dentition is either continuous or the series may be interrupted 

 by a diastema. The superior molars are either tritubercular or more fre- 

 quently quadritubercular in structure, and the protocone assumes a V-shaped 

 form ; it is joined to the external cusps by the two diverging sides, so that 

 the dental crown is trigonodont, that is, bunolophodont. If it at all enters 

 into the composition of the tooth, the hypocone always remains inferior in size 

 to the protocone. A strong basal cingulum is generally present, which some- 

 times forms an inner wall. Small intermediate conules also occur in various 

 genera. As in the ungulates, the talon on the inferior molars consists of a 

 bicuspid posterior jDortion, which in length and breadth does not fall beloAV 

 the anterior half. The latter frequently exhibits the three primitive cones, 

 although the protocone is far less robust than the two others and often dis- 

 appears completely ; hence the dental crown of the inferior molars consists of 

 two pairs of opposite or somewhat alternating tubercles, which are usually 

 united by transverse or oblique ridges. The premolars are always less com- 

 plex than the molars. While in the fossil forms three incisors, often four 

 premolars, and three molars are developed, in existing lemurs never more than 

 three premolars and two incisors are present above and below, and the first 

 premolar in the mandible exhibits a most marked and stout structure ; it 

 assumes the form and function of a true canine, yet does not like this come in 

 contact with the normally formed superior canine; but like a true premolar it 

 is inserted between the latter canine and the first superior premolar. The 

 peculiar inferior canine immediately follows the incisors and also agrees with 

 them in form and function, as in the ruminants. The superior incisors are 

 small, curved, conical, or spatulate, those below, however, being unusually 

 slender, awl-shaped, much elongated, and close together. 



