328 STNOPSIS OF THE VERTEBRATE FAUNA OF THE PUERCO SERIES. 



This sijecies is dedicated to my distiiiguislied friend Prof. Albert Gaudry, Pro- 

 fessor of Palaeontology in the Jardm des Plautes, Paris. The type specimen comes 

 from the Lower Puerco. 



MiocL^NUS INTERRUPTUS Cope. DelUitherium inlerruptum Cope, Proc. Arner. PUilos. Soc, 1883, p. 4G3 ; Tertiary 

 Vertebrata, 1885, p. 283, PI. XXIII d, fig. 13. 



The type and only specimen of this species is imi^erfect, but presents the char- 

 acter which is shared by no other in this genus, of interspaces between the second, 

 third, and fourth inferior jDremolars. The fourth premolar is not present in the speci- 

 men, whence my former reference of the species to the genus Deltatherium, but the 

 appearance of the surface of the ramus leads me to suspect that the tooth has been 

 lost by accident. The species is further peculiar in the very small anteroposterior 

 diameter of the first premolar, in which it differs from the other species where this 

 tooth is known. The fifth cusp is well-developed on the m. i, but the other inferior 

 molars, with the superior dentition, are unknown. 



MlOCL^NUS LTDKKKERIANDS Sp. nOV. 



This species is characterized by the presence on the inferior molar teeth of a 

 distinct curved ledge in front of the two principal anterior cusps, which terminates in 

 a more or less distinct fifth cusp at its internal extremity. The ledge with its curved 

 anterior edge is unusual in this genus, though more oi- less developed in some of them, 

 especially the M. opisthacus. The present species is much larger than the latter, and 

 exceeds the M. suMrigonus also, but is smaller than the M. jjrotogomoides. 



The heel is rather wide and the edges elevated and with only an external cusp- 

 like elevation, giving a basin-like surface. The last molar is not enlarged or reduced, 

 but is narrowei- than the m. ii. The crowns are without cingula, and the enamel is 

 obsoletely plicate. No premolars preserved. 



Measurements. M. 



Length of true molars OlS 



" " la.st true molar 007 



-,. .. f anteroposterior OdCi 



Diameters m. n -^ 



I transverse 00() 



_ . f anteroposterior OO.'io 



Diameters m. \ \ 



[^ transverse OO.j.i 



Deplli of ramus at m. i 014 



Poi'tions of three mandibular rami represent this species. It is dedicated to 

 Dr. Kichai-d Lydekker, the distinguished curator of vertebrate palajontology in the 

 British Museum. 



