298 PROCEEDINGS OF THE ACADEMY OF [1888, 



the two complete ones. In front of these, Prof. Owen describes 

 sockets for a bifanged tooth, (the canine), and for four single incisor 

 fangs. 



PERALESTES. 



A reexamination of the superior molars in the type maxilla of 

 this genus reveals an inconsi^icuous but important feature in tlie 

 crown which escaped Professor Owen's notice as well as the writer's. 

 That is, the presence of a low transverse crest connecting the antero- 

 internal and antero-external cusps. This puts the functional adapta- 

 tion of the Peralestes molar in a different light from that described 

 in the Memoir, since it shows that this molar is subtrenehant. A 

 close examination of the anterior faces of these crests, moreover, 

 yields some evidences of wear Idv the crown of an inferior molar. 

 These crowns ai'e placed somewhat obliquely, but when the jaw is 

 tilted so that the teeth can be viewed directly upon end, they are 

 seen to have a triangular section, with the base with its lesser cusps 

 directed outwards, and the main cone directed inwards, precisely as 

 in the primitive tritubercular crown. When viewed in this w'ay,. 

 this pattern at once suggests that of the Spalacotherium lower molars,. 

 Avhich consists of a triangle reversing the al)ove, /. e. with the main 

 cone external and the base internal. Mr. Lydekker was the first to 

 reach this conclusion as to the probable identity of these two genera 

 but upon different grounds,^ and the writer has hitherto held quite- 

 an opposite opinion,'- which is now withdrawn. 



The premolar formula of Peralestes is somewhat uncertain and the 

 molars agree in number and size with those of Spalaeotherinm. At 

 present, however, the evidence for the union of these genera is hardly 

 sufficient to justify more than the placing of Peralestes in brackets 

 with the above genus. 



STYLACODONTIDAE. 



After all tlie systematic work which Iuts been done upon the genera 

 embraced in this family, there are none in greater confusion as to no- 



' " The true molars {o( Ferakstes) agree so closely in structure with those of 

 Chrysochloris tliat there is every probahility that the specimen belongs to Spalaco- 

 therium triciispiiiens''' op. cit., p. 294 : In the writer's opinion, the molars of Chrys- 

 ochloi-is bear only a remote resemblance to those of Spalacotheiinni. 



2 " A review of Mr. Lydekker's Arrangement of the Mesozoic Mammalia." 

 American Naturalist, March, 188S, p. 23'), " The molars of this genus are widely 

 different from those of Spalacotherium etc." 



