206 



EEPTILIA 



CLASS III 



IdiocJiehjs, v. Meyer (Cheloimni/s, Jourdan). Shell with deeply emarginate 

 nuchal ; neurals frequently short and interrupted, never exceeding seven in 

 number, and not connected with the one suprapygal. Vertebral shields very 

 broad. Lithographic Stone ; Bavaria and Cerin, Ain. /. fitzingeri, v. Meyer. 



Plesiochehjs, Eut. {Stylemys, Maack, non Leidy), (Fig. 307). Shell attaining 

 a length of 0-5 m., circular or cordiform, relatively thick, considerably vaulted 



Hcsiochelys solothtrensis, Rlitimeyer. Upper Jura (Kimmerklgiaii) ; Solothuni, Switzerland. 

 Vs (after Rlitimeyer). 



in the adult, and with or without a persistent plastral vacuity. Nuchal more 

 or less emarginate ; neurals generally long and narrow, eight in number, and 

 connected with the first of the three suprapygals. Plastral bridge long ; 

 sulcus between abdominal and femoral shields ascending towards the hypo- 

 plastral suture, and terminating in the middle of the inguinal notch. Upper 

 Jura ; Germany, Switzerland, and France. 



Hydropelta, Paracheli/s, v. Meyer. U pj:)er Jura ; Euro^ie. Hylaeochelys, Lyd. 

 Upper Jura and AVealden ; Europe. 



Sub-Order D. AMPHICHELYDIA. Lydekker. 



Xa sals free ; a squamuso-parietal arch; descending 'processes of irrefrontaU 

 joining vomer ; stapes in an open groove of the quadrate ; pterygoids narroio in the 

 middle, without wing-like lateral expansions, separating quadrate and hasisphenoid ; 

 epipterygoid well developed and free; dentary bodies distinct. Cervical vertebrae 

 with well -developed transverse processes, with single articular faces, biconcave ; 

 dorsal and sacral vertebrae tvith icell- developed ribs. Pelvis not anchylosed to 

 the carapace and plastron. Epiplastra in contact with hyoplastra, entopilastron 

 oval or rhomboidal ; a complete series of marginals connected with the ribs. 



The foregoing definition of this sub-order, as given by Baur, is based 

 largely upon the genus Compsemys, Leidy, oldest North American tortoise, of 

 which nearly all parts of the skeleton are known. The group was established 

 by Lydekker to include a number of generalised later Mesozoic forms having 

 a shell constructed on the plan of that in Cr\^ptodires and Pleurodires, in 

 which mesoplastral bones and an intergular shield are develojoed. The pubis 



