604 THE MES0SAT7EIA OF SOUTH AFRICA. 



makes a resemblance to Stereostemum. It is possible that the suborder 

 Mesosauria may be enlarged hereafter, but at present it seems to 

 me convenient to include in it two divisions, the Proganosauria of 

 Baur and the Neusticosauria. These groups may be defined in the 

 following classification : — 



§ 6. Classification of the Mesosaueia. 



General Characters : — Palate closed in the median line. Teeth 

 slender, prehensile. Cervical ribs with a single articulation. Dorsal 

 ribs articulated to the anterior face of the neural arch. The 

 shoulder-girdle formed of scapular and clavicular arches. Humerus 

 expanded distally with an ent-epicondylar foramen. Digits ter- 

 minating in claws. 



Division I. Proganosauria. 



Articular faces of centrum conically cupped. Coracoid and 

 scapula anchylosed. A large clavicle [or separate episcapulas]. A 

 sacrum of four vertebrae. A foramen in the pubis. Five bones in the 

 distal row of the tarsus. Neck short ; tail long. 



South Africa ; South America. 



Division II. Neusticosauria. 



Articular faces of centrum flat. Coracoid and scapula separate. 

 Clavicles relatively small [no separate episcapulal. Sacrum unknown. 

 A notch instead of a foramen in the pubis. Neck long ; tail short. 



Europe. 



I wish in conclusion to express my thanks, for the loan of speci- 

 mens and for facilities in making these observations, to the Trustees 

 of the South African Museum, Cape Town ; to the Committee of the 

 Albany Museum, Grahamstown ; to Dr. Henry Woodward, P.R.S., 

 and the Officers of the Geological Department of the British Museum 

 (Natural History) ; and to the Government Grant Committee of the 

 Eoyal Society for assistance. 



EXPLANATION OF PLATE XYIII. 



Fig. 1. Dorsal aspect of dorsal vertebrse and ribs of Mesosaurus fleurog aster 

 (Brit. Mus., Nat. Hist.) ; n = neural arch ; v = transverse process ; 

 c = centrum. 



2. Portion of ventral armour of the same specimen. | 



3. Ventral aspect of a specimen showing abdominal ribs. 



4. Impressions of early caudal vertebras ; and hind foot of the same 



animal. 



5. Ventral aspect of the anterior part of the skeleton of Mesosaurus tenui- 



dens (South Afr. Mus., Cape Town). 



