226 



REFTILIA. 



may be left a median space, closed by skin or cartilage (Trionyx, 

 Chelonia, etc.). The spinous processes and ribs of the thoracic vertebrae 

 take part in the formation of the large carapace, as well as a number 

 of paired and unpaired osseous dermal plates, which are placed partly 



FIG. 646. Skeleton of Cistudo (Emys) europaea. V, vertebral (neural) plates; C, costal 

 plates ; M, marginal plates ; Nu, nuchal plate ; Py, pygal plate ; B, plastron (ventral 

 shield) ; Cl, clavicle ; Jcl, inter-clavicle ; Sc, scapula ; Co, coracoid ; Pco, acromial 

 process (pro-ceracoid); Pb, pubis ; Js, ischium ; Jl, ilium ; H, humerus ; JB, radius ; 

 U, ulna; Fe, femur; T, tibia; F, fibula. 



in the median line in the neck (nuchal plate), and in the sacral region 

 (pygal plate), and partly laterally at the edge of the shield (22 mar- 

 ginal plates). 



While the spinous processes of eight of the thoracic vertebrae (2nd 



