204 EEPTILIA class hi 



separating the quadrate and ha&isphenoid ; nasals free or united with prefrontals ; the 

 latter without descending processes. Neck bending laterally; cervical vertebrae with 

 strong transverse processes and single articidar faces. Shell usually covered with 

 epidermal shields; a complete series of marginal bones connected with the ribs; 

 epiplasfra in contact with hyoplastra ; mesoplastrals present in some forms, and an 

 intergular in all cases where epidermcd shields occur. Pelvis anchylosed to carapace 

 and plastron. Digits tvith not more than three phalanges. 



In this group, as indicated by the name, the neck bends laterally, and the 

 pelvis is anchylosed to the carapace and plastron. A number of fossil forms 

 are known which exhibit characters intermediate between Pleurodires and 

 Cryptodires, and are here considered (following Baur and Lydekker) as an 

 independent sub -order, the Amphichelydia. Existing Pleurodires are re- 

 stricted to the southern hemisphere, and distributed in South America, 

 Southern India, Africa, and Australia. 



Family 1. Proganochelyidae. 



Containing only the primitive Proganochelys, with the characters of that 

 genus. 



Proganochelys, Baur (Psammochelys, Quenst. ; ? Chelytherium, von Meyer). 

 The following description of this, the most ancient of all Chelonians, is 

 condensed from Fraas ; known only by the carapace and plastron, in one 

 specimen about 065 m. long and nearly as wide. Carapace moderately convex, 

 with five vertebral shields greatly enlarged and the costals corresj)ondingly 

 reduced ; a series of supramarginal epidermal scutes at the antero- and postero- 

 lateral angles, elevated into prominences ; posterior marginals large and freely 

 projecting. Neural bones small, costals large and extending with the rib ends 

 as far as the plastron. Sternal bridge long, mesoplastrals very large, laterally 

 expanded, and meeting in the middle line ; epi- and ento-plastron ver}' small. 

 Pelvis supported by two sacral vertebrae ; ribs and pelvis connected with the 

 carapace and plastron. Upper Trias (Stuben Sandstone) ; Wiirtemberg ; 

 P. quenstedtii, Baur { = Psammochelys keuperiana, Quenst.). 



Family 2. Miolaniidae. Owen. 



Shell known only by fragments. Skidl with completely roofed temporal fossae, and 

 furnished with horn-like bony protuberances; no distinct nasals; vomer dividing 

 palatines. Caudal vertebrae opisfhocoelous, with chevrons ; tail long and encased in a 

 nodose bony sheath. Pleistocene. 



Miolania, Owen (Ceratochelys, Huxley). Cranium with three pairs of 

 peripheral prominences in the fronto-parietal region, the head measuring in 

 one species 0*6 m. in width to the tip of the " horns." Habits probably 

 herbivorous and terrestrial. Eelated to the Testudinidae, according to Baur. 

 Pleistocene ; Queensland and Lord Howe's Island. M. platyceps, Owen ; M. 

 oweni, Sra. "Woodw. 



Family 3. Ohelsridae. Gray. 



A strong parieto-squamosal arch; posterior narial openings bounded by maxillae, 

 palatines, and vomer ; frontal unpaired ; nasals free ; premaxillae district. Shell 



