71 



upper part by the medullary artery. Dorso-lumbar vertebrae, generally, 

 nineteen in number (d. 12 15-j-l. 7 4.) Skull witli the intermaxillary 

 bones flattened above towards the symphysis, and with the incisors, when 

 present, diverging towards their roots. Stomach more or less subdivided 

 er complex: coecum comparatively small and simple. 



ARTIODACTYLA. 



II. Digits unpaired or unequal, the third being the largest and most exserted ; 

 (the fourth nearly co-equal in size and position with the second; fifth 

 of hind foot, at least, atrophied;) the articulating phalanges and carpal 

 and tarsal bones correspondingly modified. Astragalus with the anterior 

 or inferior articular surface divided into two very unequal facets. Femur 

 with a third trochanter, and with its shaft perforated at the back-part by 

 the medullary artery. Dorso-lumbar vertebrae not less than twenty-two 

 in number (d. 18 19-f-L 3 6). Skull with the intermaxillary bones 

 tectiform above and united towards the symphysis, and with the incisors, 

 when present, implanted subvertically and nearly parallel to their roots. 

 Stomach simple : coecum very much enlarged and sacculated. 



PERISSODACTYLA. 



AUTIODACTYLA. 



FAMILIES. 



I. Molars (M) attypically each with two double crescentiforrn folds, whose 

 convex surfaces are internal. Canines of lower jaw, attypically, re- 

 sembling, and parallel with, incisors ; (differentiated and specialized in 

 Camelidae). Palatine bones contracted and compressed behind, thin, and 

 (at the walls of the posterior nares) separated by a wide sinus from the 

 terminal portion of the supramaxillary bones. Digestive system adapted 

 for rumination : stomach tripartite, or, attypically, quadripartite, a " psal- 

 terium" being finally developed. Axis with the odontoid process like 

 a spout, or hollow half-cylinder, and with a prominent sharp semi-circular 

 rim. (Flower.) (Pecora; or, Ruminantia.) 



* Incisors deciduous from upper as well as lower jaws. Canines of lower 

 jaw inclined forwards, with compressed cuneate crowns. Placenta and 

 stomach unknown. Chalicotheroidea. 



One family. CHALICOTHERIIDAE. (XXVII a.) 



** Incisors persistent in lower jaw. 



A. Hind limbs with the proximal joint (femur) exserted and not contain- 

 ed within the common integument. Canines of lower jaw specialized 

 and differentiated from incisors. Incisors in part (z. e. lateral) persist- 

 ent in upper jaw. Placenta diffuse. Stomach imperfectly quadripartite. 

 {Pecora tylopoda s. phalangigrada.) 



One family. CAMELIDAE. (XXVIII.) 



B. Hind limbs with the proximal joint (femur) not exserted but inclosed 

 within the common integument. Canines of lower jaw similar to and 



