SUBORDER B DILAMBDODONTA 45 



Lower M tuhercido- sectorial with fairly high trigonid and large, low talonid. 

 Lower Eocene of Europe. 



The shape of the lower jaw and the nature of the dentition indicate that 

 we probably have to deal with the ancestral stock of rodents. 



Plesiadapis Lemoine. Lower Eocene of Rheims and Belgium, possibly 

 also in the Bohnerz of Egerkingen. 



Protoadapis Lemoine. 2.L3.3. Without diastema. Eocene of Rheims, 

 France. Systematic position uncertain. 



Family 10. Pantolestidae Matthew. 

 C normal. Upper I isolated, P simple and trerichant. Upper 



3.1.4.3. 



M trit'ubercular, lower tuhercido -sectorial with tricuspidate trigonid and talonid. 

 Snout short and broad, cranium long and wide, with high supraoccipital crest and 

 weak sagittal crest, without ossified bulla. 



The Pantolestidae were at first considered as Artiodactyla. Matthew 

 now classes the type species as insectivore on account of the characters of the 

 skeleton, the presence of a mental foramen below M, and the short, broad snout. 

 Were it not for these characteristics they might also be placed under the 

 head of creodonts. The much-curved humerus has a well-developed deltoid 

 crest and an entepicondylar foramen, the femur has a third trochanter, and 

 tibia and fibula are distally co-ossified. The astragalus has a broad, furrowed 

 trochlea and a short neck, the claws are flattened and broad. The tail is 

 rather long. The extremities show adaptation to aquatic life. 



Pantolestes Cope (Passalacodon, Anisacodon Marsh). Paraconid small. 

 Middle Eocene (Bridger beds). 



Palaeosinopa Matthew. Paraconid well developed. Lower Eocene 

 (Wasatch beds). 



Pentacodon Scott. Lower Eocene (Torrejon beds) ; New Mexico. 



1 Ptolemaia Osborn. Paraconid weak. I and foremost P reduced. 

 Oligocene ; Egypt. 



Family 11. Tillodontidae {Tillodontia Marsli).i 



Extinct, pentadactyl, clawed plantigrades with enlarged and rodent-like Z, and 

 brachyodont M. Upper M tritubercidar, with secondary tubercles, lower with high 

 semicircular ? trigonid and a somewhat lower semicircular talonid. Scaphoid 

 separated from lunar. 



The skull is on the whole carnivore-like. The breadth of snout and occiput, 

 the lack of postorbital contraction and the nature of the auditory region — 

 flat bulla — as well as the shape of the articulation of the mandible emphasise 

 the connection of this family with the insectivores. The diff"erentiation 

 between / and also agrees with this interpretation. The first pair of 

 / are lost, the second pair enlarged, the C pass into small intermediate teeth, 

 and accordingly the hinder P become ilf-like. 



^ Cope, E. I)., Vertebrata of the Tertiary formations of the west, 1877. — Tertiary Vertebrata, 

 \%M.— Gregory, W. K. Bull. Amer. Mus. Nat. Hist., 1910, p. 292.— Marsh, 0. C. Aiuer. 

 Journ. Sci., 1875, vol. ix. ; 1876, vol. xi. 



