WEALDEN CHELONIANS. 183 



half of the hyposternals. The femoral scutes {fe) were longer than they were 

 broad ; thej joined the abdominal scutes by a straight transverse line ; but that 

 between them and the anal scutes {a n) describes a curve, with the convexity back- 

 wards, and nearly equally divides the xiphisternals [x s). In addition to the axillary 

 and inguinal scutes, there are three scutes interposed between the outer borders 

 of the pectoral and abdominal scutes, and the under borders of the fifth, sixth, and 

 seventh marginal scutes : these superadded scutes I propose to call " submarginal 

 scutes." The Platysternon megacephahmi, or Large-headed Terrapene of the 

 Chinese swamps, presents a corresponding, but single, supplementary " submar- 

 ginal scute " upon the under part of each lateral production of the plastron. The 

 under surface of the fifth, sixth, and seventh marginal plates bears a crucial 

 impression, indicative of the lines of junction between the marginal and submar- 

 ginal scutes. The head of the left femur is preserved, near the seventh marginal 

 plate, in the specimen above described. 



Pleueosteenon emaeginatum, Owen. Plates 55, 56. 



This is a nearly-allied species. It is from the same formation and locality, and 

 differs from the foregoing chiefly in the contour of the free borders of the 

 plastron. The nuchal and first marginal scutes are wanting in the specimen with 

 the upper surface of the carapace exposed (PI. 55). The neural plate answering 

 to (s i) in ordinary Chelonia is divided by a transverse suture in this species, 

 as in PI. concinnum, and the impression of the line of union between the first and 

 second vertebral scutes crosses just in front of the suture of division. The second 

 neural plate (2) joins the first costal plate of the left side, but not that of the right ; 

 and it is pentagonal, the shortest side or border being that which joins the left 

 first costal plate. The third (3) to the seventh (7), neural plates inclusive are 

 hexagonal, and resemble in shape those in the Plem-osternon concinnmn ; the eighth 

 neural plate is hexagonal, and is broader than it is long ; the ninth neural plate 

 answering to that bearing the letter (« s) in PI. 53, is more expanded at its hinder 

 part ; the tenth neural plate (10) is triangular, with a truncated apex and a broad 

 rounded base, which articulates with the pygal and adjoining marginal plates. The 

 second and third marginal plates bear not only the impressions of the lines 

 dividing the corresponding marginal scutes from each other, but those dividing the 

 marginal from the first costal scutes. The succeeding costal scutes do not encroach 

 on the marginal plates, which consequently only show the impressions dividing the 

 marginal scutes from each other. Some of the marginal scutes are slightly 

 dislocated, and the posterior ones, from the ninth to the pygal scute inclusive, have 

 their free borders mutilated. 



