CHARACTERS OF LEMURS 88 1 



claw, but the others usually have flat nails ; the cerebral 

 hemispheres are but slightly convoluted, and do not com- 

 pletely overlap the cerebellum (except in Indrisinae) ; the 

 middle or transverse portion of the colon is almost always 

 folded or convoluted on itself ; there may be abdominal and 

 inguinal as well as pectoral mammae ; the uterus is bicor- 

 nuate ; the urethra perforates the clitoris (except in 

 Chiromys) ; the placenta is diffuse and non-deciduate 

 except in TarsiuSy where it is metadiscoidal and deciduate. 

 Among other features we may note that the Lemurs are 

 plantigrade and usually pentadactyl ; the tail (sometimes 

 reduced) is never prehensile ; the mandibles are often 

 unfused at the junction ; in the Madagascar forms the 

 tympanic remains a half-ring within the bulla which is 

 due to the periotic ; the carpus has a centrale usually 

 free ; there is a large caecum without a vermiform appen- 

 dix ; there are often retia mirabilia on some of the arteries 

 and veins. 



The lemurs are small, furry quadrupeds, with fox-like faces but 

 the general appearance of monkeys. Most are nocturnal, all arboreal. 

 They feed on fruits and leaves, on eggs and small animals. Most are 

 loud-voiced. They are usually uniparous. 



A. Madagascar Lemurs, with the tympanic annulus free in the bulla. 

 Family Lemurinae, with long faces. Some have tufts of vibrissas 



on the forearm, and a forearm gland, with spines in the male. 

 Family Indrisinag, with short faces, cerebrum covering cerebellum. 

 Family Chiromyinae, with Chiromys, the Aye-Aye, highly speci- 

 alised, e.g. with very long slender third finger, with a flat nail on 



the thumb only, with rodent-like permanent incisors (^-^), 



with inguinal mammae. 



B. Ethiopian and Oriental Lemurs, with the tympanic sharing in 



making the bulla. Family Galaginae, with one type Galago, 

 with elongated calcaneum and navicular. It occurs right across 

 Africa. Family I.orisinae. Asiatic and African. 



C. The aberrant Indo-Malayan Tarsius, with many peculiarities, e.g. 



the orbit comm\micates with the temporal fossa only by a fissure, 

 the upper incisors are close together, the calcaneum and navicular 

 are greatly elongated like the calcaneum and astragalus in the 

 frog, the placenta is metadiscoidal and deciduate as in monkeys. 

 Important as a stage in the differentiation of the cerebral neo- 

 pallium, e.g. the predominance of visual over olfactory areas. 



The lemiirs are interesting as links between Antkropoidea and 

 lower Mammals, and because of their distribution. In Eocene times 



S6 



