1883.] dlO [Cope. 



cingulum present. External cusps rather small, separate. Intermediate 

 cusps present ; V large and distinct. Enamel smooth. 



The inferior true molars support Vs ; in the second the anterior is 

 smaller and is more elevated than the posterior. The latter is continued 

 as a raised posterior, and partly interior border of the heel, without promi- 

 nent cusp. The crown has a distinct external and a very faint internal 

 cingulum. In the supposed first true molar, the anterior V is more pro- 

 longed anteroposteriorly as in the corresponding tooth of Mioclmnus ferox, 

 etc., and the fourth premolar of Phenacodus primcevus. The anterior 

 cusp is the lowest. The heel supports three low cusps, of which the ex- 

 ternal has a crescentic section, and the posterior is the smallest. 



It is probable but not certain that the fourth premolar has an internal 

 cusp, as the tooth, presumably this one, is injured at that point, Should 

 the internal cusp be absent, this species cannot be referred to Ghriacus. 



Measurements. M. 



Length of superior true molars 0135 



/ anteroposterior. 005 



Diameters of first true molars { transyerse 006 



„. „ , . , f anteroposterior 0053 



Diameters of second true molars < * „„„ 



I transverse 007 



_.. ».,. , , , [anteroposterior .0034 



Diameters of third true molar < ... 



I transverse 006 



_,. . „„,.„; , /anteroposterior.. .005 



Diameters of first inferior true molars . ,,_._ 



(-transverse 0035 



_.. . ■ . „ . , /anteroposterior .0056 



Diameters of second inferior true molar i , __.„ 



<- transverse 0043 



D. Baldwin, discoverer. 

 Tricentes crassicollidens, gen. et sp. nov. 



Char. gen. This genus is Ghriacus with only three premolars in the su- 

 perior, and probably inferior series. The canines are well developed, and 

 lateral in position, leaving space for small incisors, thus differing from the 

 genera of the Mixodeciidm, Mixodectes, Microsyops, andGynodontomys, on the 

 one hand, and from Necrolemur on the other. It has, so far as known, the 

 dental formula of several genera of typical Lemuridse, but differs from these 

 in the following points. The orbit is open posteriorly ; the inferior molars 

 have the anterior triangle of three cusps ; and the fourth inferior premolar 

 has an interior cusp. I have demonstrated the last mentioned characters 

 on the type, T. crassicollidens only, but suspect its presence on some or all 

 of the other species. In their details the superior true molars are like those 

 of Mioclsenus, as distinguished from those of Pelycodus. 



To this genus belongs the Mioclcmus subtrigonus, and probably, from the 

 small size of its fourth premolar, the M. bueculentus. I add to these three 

 a fourth, T. incequidens, and remark that it is yet uncertain how many pre- 

 molars are present in the Ghriacus simplex. Should the latter possess 

 three only, it will be properly referred to Tricentes. 



