57 



and nintli marginal plates laterally expnnded, twice as br<ni(l 

 as those above tlie bridge. Proflle ol: back considerably elevated 

 and rounded, deepest in front';of^the;,bridge on second vertebral 

 plate. A deep curvature above and beyond the bridge from 

 the fifth to eighth lateral plates. Nuchal plate one-seventh 

 longer than broad, quadrilateral : niargino-nuchal plates much 

 longer on the outer than the inner edge, the latter being equal 

 to the'i breadth : margino-brachial plates quadrangular, the 

 breadth of the first pair four-sevenths of the length, with the 

 anterior and posterior margins equal ; second pair with the 

 anterior margin nearly twice as long as the posterior : first 

 pair of margino-lateral plates very narrow, more than three 

 times as long as broad, and much longer but not so broad as 

 the second margino-brachial ; second and third pairs nearly 

 rectangular ; fourth pair longer externally and posteriorly ; 

 fifth pair quadrilateral and rectangular, slightly longer than 

 broad: first pair,o£ margino-femorals as broad as the inner 

 edge, which is slightl^^ less than the outer ; second and third 

 pairs quadrilateral, longer than broad, with the inner edges 

 the shorter : supra-caudals convex on the outer edge, forming 

 a shallow notch at the symphysis, about two-thirds as broad 

 as long, and very distinctly arched at the suture. First 

 vertebral plate octagonal,* larger than the others, in conjunction 

 with the nuchal, margino-nuchal, and anterior half of the first 

 margino-brachial ; posterior edge deeply concave : second and 

 third hexagonal : fourthf hexagonal (?) with the anterior edge 

 twice as long as the posterior : fifth plate quadrilateral, its 

 anterior edge but one-third of the length of the posterior, 

 which barely touches the last margino-femoral, and is not 

 perceptibly angulated. Posterior costal plates as high as the 

 lower edge ; anterior plates very large, the outer edge nearly 

 one-half longer than the first vertebral plate, measured along 

 its central line. All the plates of the carapace, densely and, 

 with the exception of the marginal plates, deeply sculptured ; 

 for the most part this sculpturation is most eccentric in 

 character, consisting chiefly of a network of deep grooves 

 enclosing nodules of many shapes and sizes ; on the middle 

 vertebral plates, however, it takes a more or less regular 

 longitudinal form, while on the lower half of some of the 

 costal plates, a tendency to a transverse ornamentation may 

 be traced : plates of the plastron and bridge distinctly marked 

 by a network of grooves, scarcely perceptible to the touch. 



* In the type specimen, which is as yet unique, there is on the left 

 side a small plate intercalated between the first vertebral and first costal 

 plates, and standing on the anterior margino-brachial plate, but from 

 an examination of the opposite facies it is evident that this is accidental. 



fThis plate in our specimen is broken up into two parts, evidently 

 by an accidental fracture, the hinder part being small and subcircular. 



