Marsh Collection, Pedbody Museum. 405 



Megaladapidse. It should be remembered, however, that the 

 Leniuridse, as thus constituted, include forms of very diverse 

 structure and probably not very closely related. Thus the 

 Indrisinse, usually considered as one of the best-marked and 

 most distinct subfamilies, in the absence of one pair of incisors 

 or canines in the lower jaw, together with the strongly 

 developed mesostyle of the superior molars, appear to be suffi- 

 ciently differentiated from the central forms of the typical 

 lemurs to be entitled to a distinct family rank. 



The third and last primary division of the order is the 

 Anthropoid ea, and in the present state of our knowledge it 

 seems quite impossible to obtain any very clear insight into 

 the phyletic history of the various groups composing it. Until 

 much additional information is secured concerning many of the 

 fossil types already known, as well as of the large number of 

 undiscovered connecting forms which must have certainly 

 existed, any attempts at a classification that may be regarded 

 as final can not at present be made. Still, certain advance 

 steps may, I think, now be taken, which will help considerably 

 toward a final solution of some of the many difficult problems 

 involved in unraveling the tangled web of simian evolution. 



The characters by means of which the members of the group 

 are distinguished from the two foregoing suborders are as fol- 

 lows : Incisors reduced to two pairs above and below (in Tar- 

 sius, one below) ; they have a normal form and position ; there 

 is no caniniform enlargement of the first lower premolar ; the 

 entocarotids traverse the petro-tympanic ; the lachrymal canal 

 (except in one group) is more or less confined within the orbit, 

 and the facial part of the bone is quite generally reduced ; the 

 lachrymal and malar are not in contact, leaving the maxillary 

 a share in forming the anterior rim of the orbit ; the fourth 

 digit of the manus is never the longest of the series. 



It would appear from present evidence that the Anthropoidea 

 early divided into at least three main branches, but the exact 

 lines of descent from these starting points can not now be 

 traced with any degree of certainty, among the majority of the 

 living species. The first of these divisions is represented by 

 the living marmosets, a group which Huxley classified under 

 the name of the Arctopithecmi.* Their chief claim to dis- 

 tinction consists in the lack of opposability of the hallux and 

 pollex ; the clawed condition of all the terminal phalanges of 

 both manus and pes, except a slight flattening of that of the 

 hallux ; the loss of the third molar above and below, and the 

 tritubercular condition of the superior molars. These charac- 

 ters, except the last, are unique among the Primates, and may 

 or may not indicate a very ancient branching from the main 

 * Anatomy of Vertebrated Animals, 1872, p. 392. 



