508 MR. ST. G. MIVART ON THF LEMURS. [May 20, 



difference, it should be remembered that amongst Apes we find in 

 Ateles an extraordinary elongation of that organ, while no naturalist 

 would think of separating from the orders Insectivora and Rodentia 

 such forms as Talpa, Arvicola, Lagostomus, and Bathyergus because 

 in them this structure is, as in the Lemuroids, perforated by the 

 urethra. 



Nevertheless whatever objections may be made to the above di- 

 stinctive characters taken one by one, it is not, I think, to be con- 

 tested that, taken together, they render it in the highest degree im- 

 probable that the Lemuroids and Apes took origin from any common 

 root-form not equally a progenitor of other Mammalian orders. 

 Consequently, if genetic affinity is to be our standard, the Lemuroidea 

 should rank as a distinct order. Considerations, however, have been 

 already advanced against the adoption of such a standard ; and yet 

 other reasons will, I think, become obvious from a consideration of 

 minor groups. 



As to the second question then, namely the value of the characters 

 which define subordinate groups, it may be well to compare toge- 

 ther the Simiadce and Gebidce. 



If the difference as to the development of the pollex in Lemuroids 

 and Apes is of weight, why is not as much weight to be attached to 

 the entirely different character of that organ in the two great groups 

 of Apes 1 



If the dental distinctions between Lemuroids and Apes are to be 

 considered to tell against genetic affinity, why should not the com- 

 bined diminution of molars and augmentation of premolars so tell 

 also in Hapale 1 



If an oblique ridge on the grinding-teeth can arise independently 

 in Galago and Ateles, why may it not arise independently in Ateles 

 and Simia 1 



If the absence in one case of a postorbital extension of the ali- 

 sphenoid and malar counts against the common origin of Lemur and 

 Cynocephalus, why should not the absence of a bony meatus audi- 

 torius externus in Mycetes also count against its affinity to Cyno- 

 cephalus also 1 



If the greater relative size of the anterior hyoidean cornua is a bar 

 to the assignment of a common origin between Galago and Colobus, 

 why should not the presence of a jointed anterior cornu in Lagothrix 

 form a bar to the assignment of a common origin to that Ape and to 

 Colobus 1 



I must confess that I find it exceedingly difficult to conceive that 

 the universal presence of a long bony meatus auditorius externus in 

 the Simiadce and its equally universal absence in the Gebidce can be 

 accounted for any exigences of the struggle for life upon incipient or 

 primordial Ape-forms. 



To this character must be added the many others which divide 

 the Apes of the two hemispheres, namely : — (1) their different denti- 

 tion ; (2) the broad nasal septum of the New-World Apes ; (3) the 

 tendency of the Gebidce to a curled tail-end, and the constant absence 

 of any manifestation of such a tendency in the Simiadce ; (4) the 



