442 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Of the five vertebral plates, the anterior is pentagonal, the two pos- 

 terior angles right angles; the second and third are hexagonal, the 

 anterior and posterior lateral margins approximately equal; the fourth 

 is hexagonal, the jiosterior lateral border longer than the anterior lat- 

 eral and carved inward; the fifth is hexagonal, the anterior lateral bor- 

 ders longest. The first lateral plate is quadrilateral (or resembles a 

 triangle with a rounded apex), the lower border presenting rounded 

 angles, and joined to the first four marginal plates; the second and 

 third are hexagonal, the lower angle very obtuse; the posterior is quad- 

 rilateral and in adults nearly square. There are twenty-four marginal 

 plates. The nuchal is small, quadrilateral, largest in front, or square; 

 the supra-caudal is quadrilateral, but considerably less than twice as 

 broad as high. The marginal plates differ much in different specimens. 

 The first is rudely pentagonal, usually with an acute angle directed 

 toward the nuchal; the remainder are irregularly quadrilateral; the 

 sixth, however, is sometimes ijlainly pentagonal. In adults, the center 

 of the eighth, ninth, tenth, and eleventh plates is usually strongly de- 

 pressed, the free border being revolute. 



The sternum is broad and convex at the sides, and extends an inch or 

 less beyond the carapace in front. Each gular plate is quadrilateral. 

 They are united, the anterior border of the resulting pentagon being 

 invariably emargiuate, often very strongly notched. The nuchal plates 

 change shape to a remarkable degree from youth to maturity. In the 

 newly-born animal they are broad and short, but in the adult they are 

 narrow and elongated. The brachial are quadrangular; in the adult, 

 both free and posterior borders convex. The thoracic are rudely quad- 

 rilateral, and very narrow at their juncture in the median line. The 

 femoral are quadrilateral, very long and broad, covering more than a 

 third of the sternum; the anterior and posterior borders i)arallel. The 

 abdominal are rhomboidal, the exterior side longer than the interior, 



and convex. The sub-caudal are quad- 

 rilateral, with a notch of medium depth 

 between them posteriorly. The axillary 

 are usually three in number — one large 

 one between two small ones. The in- 

 guinal are also three in number, ar- 

 ranged as are the axillary plates. 



The head is slightly elongated, deep, 

 and from the eyes forward wedge- 

 shaped; it is covered with flat scales of 

 Fig. III.— X. Bkrlandieri. moderate size which in adults are ap- 

 Contour of bead obtained as before, proximately equal. In the young the 

 scales on the fore part of the head are clearly larger than elsewhere and 

 are divided into pairs, but these distinctions become uuappreciable in 

 the adult. There is usually also one very large scale over the tympanum. 

 Nostrils moderate. Eyes large, set obliquely, and looking slightly for- 



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