CLASSIFICA TION OF VER TEBRA TA 42 



l>"*!lpodidae. Neotropical, Recent: 



1 >asyj)us, Piiodon, Tatusia, Chlamydophorus. Plistocene : 

 Hoplophorus, Glyptodon, etc. 

 2. Order Trogontia, Haeckel. Terrestrial, plantigrade, 

 pentadactyle (unless the first digit is reduced as in some 

 Rodentia). 



Clavicles mostly strong. 



Tendency of the second pair of incisors to excessive, ro- 

 dential development, and gradual suppression of the first and 

 lird pair of incisors. Canines reduced or lost. 



1. Sub-order TILLODONTIA, Marsh. Pentadactyle, with 

 laws. Dentition complete ; second incisor largest. 



.Mandibular condyle transverse. 

 Humerus with entepicondylar foramen. 

 Femur with third trochanter. 

 Lissencephalous. Eocene. 



Esthonychidae. Esthonyx. Lower Eocene of North America 

 id England. 



Tillotheriidae. Tillotherium. "Wyoming. 

 Stylinodontidae. Stylinodon. North America and 

 Europe. 



2. Sub-order TYPOTHERIA, Zittel. Digits = 5 - . One 



' ° 5 or 4 



)air of upper incisors enlarged. Molars prismatic, high, mostly 

 rootless. Mandibular condyles roundish. With entepicondy- 

 ir foramen, and with third trochanter. Tertiary. 



Protypotheriidae. Protypotherium. Mid-Tertiary, Pata- 

 mia. 



Typotheriidae. Typotherium, new Tertiary. Pachyrucos. 

 tertiary, Patagonia. 



3. Sub-order RODENTIA, Vicq. d'Azyr. Digits 57^-3- 

 second pair of incisors much enlarged and rootless ; the others 

 mch reduced or lost. Canines absent. Mandibular con- 

 lyle longitudinal. Clavicles weak or absent. 



Uterus bicornis. Placenta discoid, deciduous. Cosmo- 

 politan, few in Australia and Madagascar. About 900 recent 

 species. 



Lagomorpha, Brandt. Incisors f; one small incisor is 

 placed behind the much enlarged second. Fibula articulating 



