536 Dr. C. I. Forsyth Major on the 



metacone, which in Centetidge continually advances further 

 inwards, gradually replaces in function the " protocone " 

 (talon), which in consequence becomes superfluous. In the 

 interpi'etation of the homologies the two have been pretty 

 generally confounded with each other, «*. e. paracone + meta- 

 cone is regarded as the " protocone." 



As I would finally point out yet once again, the three 

 main cusps of the crown — upon which the theory of the tri- 

 tubercular form of the dentition of Centetidse is based — accord- 

 ingly consist externally of the two most strongly developed 

 of the outer cusps, the parast7/le and metastyle of Osborn, and 

 internally (apex of the triangle) of the paracone + metacone, 

 united to form a single cusp. In cases where similar forms 

 occur among the Lemurida? the two outer cusps are consti- 

 tuted by the paracone and metacone. Like Winge, I have 

 interpreted * the apex in Lemuridae as being homologous with 

 the " protocone " of other mammals — Winge's 6. 



With regard to the lower molars I can express all that I 

 need to say here in a very few words. A characteristic 

 feature in these teeth is the extensive reduction exhibited by 

 the " talon," which usually appears only as a low posterior 

 basal cusp. The lower molars, therefore, essentially consist 

 of the anterior trigon (Osborn's " trigonid ") alone. When 

 we consider that the talon (Osborn's " talonid ") is developed 

 to the fullest extent among mammals belonging to the Lowest 

 Tertiary f and Upper Cretaceous \ Beds, it appears, in con- 

 nexion with all that has been stated above in the case of the 

 upper molars, unjustifiable to wish to regard the form of the 

 lower molars in Centetidse as of a primitive type. 



IL The Antemolars. 



Leche remarks § with reference to the upper incisors and 

 canines of Centetidee {Microgahj EriculuSj Centefes), that 

 they are provided with accessory cusps more abundantly in 



specialized and forms a parallel to Centetidse, and still more to Chryso- 

 chloridse, that this fusion likewise occurs in all molars ; tlie protocone in 

 Notoryctes is still developed to a considerably greater extent than in 

 Centetidae. 



* " On Megaladapis &c." {vide suprd), p. 23, text-figs. 1 and 2, 



t Cf. Lemoine, " Etude d'ensemble sur les dents des Mammiferes 

 fossiles des environs de Reims," Bull, Soc. Geol. de France, 3^ s^rie, 

 t. xix. 1891, pis. X., xi. 



X Cf. H. F. Osborn, " Fossil Mammals of the Upper Cretaceous Beds," 

 Am. Mus. Nat. Hist. vol. v. art. xvii. (New York, 1893), pi. viii. 

 figs. HI, Al. 



§ Anat. Anz. xiii. p. 520. 



