1873.] MR. ST. G. MIVART ON THE LEMURS. 507 



ones, and that the two groups are no more genetically united to each 

 other than is either one of them to the Carnivora or Cheiroptera. 

 Hut even if this is not the case, and if both groups really are the de- 

 scendants of some special but remote common ancestor, nevertheless 

 the number of subdivisions necessary to classify the Artiodactyla is 

 so great as possibly to justify, on that ground, the elevation of that 

 group to the rank of a distinct order. As to the question respecting 

 the zoological value of the Lemuroidea, there can, I think, be no 

 doubt that Man, Apes, and Half-Apes together constitute a group 

 capable of convenient and very distinct zoological definition 



The group may be thus defined : Unguiculate clavicul'ate pla- 

 cental mammals, with orbits encircled by bone; three kinds of teeth 

 at least at one time of life ; brain always with a posterior lobe and 

 calcanne fissure ; the innermost digits of at least one pair of extre- 

 mities opposable; hallux with aflat nail or none; a well-developed 

 cacum; penis pendulous; testes scrotal; always two pectoral 

 mammce. 



The group thus characterized, is sharply marked off from every 

 other order of Mammals, while its common characters are suffi- 

 ciently numerous and important to make a coherent whole in spite of 

 the diversity existing between the two subordinal sections into which 

 it is divided. 



Moreover the number of forms contained in the order is not ex- 

 cessive, nor is the amount of subdivision requisite for classification 



We may now turn to the subdivisions of the order, and seek an- 

 swers to the three following questions :— 1. What are the characters 

 separating the Lemuroidea from the Anthropoideal 2 What is 

 the value of the characters which define subordinate groups of Pri- 

 mates ' 3. What is the more prudent course as to the classification 

 ot such forms as may seem to be probably or possibly distinct in 

 their origin ? J 



The characters which divide the Lemuroidea from the Anthro- 

 poidea are as follows : — 



1 . Orbit opening widely into the temporal fossa. 



2. Lachrymal foramen on the cheek. 



3. Cerebellnm much uncovered. 



4. Posterior cornu of lateral ventricle very small. 



5. Pollex always large. 



(i. Index of foot with a sharp claw. 



7. Posterior cornua of os hyoides shorter than the anterior cornua 



8. Clitoris perforated by the urethra. 



9. Uterus two-horned. 



10. Placenta bell-shaped, diffuse, and non-deciduate. 



1 1. Allantois very large. 



The more important of these characters have already been reviewed 

 and reasons have been advanced tending to show the uncertainty" 

 which hangs over them as to the question of their adaptive or genetic 



With regard to the clitoris, which offers so apparently striking a 



