336 AMERICAN TESTUDINATA. Pakt II. 



ward, is straight, and parallel to the flattened part of the lower surface. The spinous 

 apophyses of the back are very long; longest about midway of the body, a Uttle 

 shorter toward the neck, and shortest at the meeting with the sacrum. Thus 

 the median longitudinal line of the upper surface is high above the column ; it 

 arches from end to end, descending much lower behind than before ; it reaches 

 far forward over the neck.^ The upper surface is broad, bluntly curved at the 

 front end, and narrower and more pointed behuad ; it reaches far forward in 

 front of the arch of the first and second pairs of ribs, but arches little from side 

 to side, and the bulk of the body is below the outer edge ; it is depressed on 

 either side of the middle longitudinal line, along where the ribs first meet it in 

 passing out from the vertebrte. The outer edge is high above the base upon 

 which the body rests ; it Mis from the front end to about midway, then rises 

 over the hind legs, and again falls behind the pelvis, where it is lowest. The 

 flattened lower surface is long and rather broad ; it reaches forward somewhat 

 farther than the upper surface, and backward to the hind edge of the pelvis; 

 it is broadest nearly under the third pair of ribs, where it has about half the 

 width of the body ; it narrows liut little forward, having a blunt, broad front 

 end, but backward it narrows faster, and at its hind end has about the same 

 width as the pelvis ; it rises somewhat from the region where it is broadest to 

 the front end. 



It is important to notice, that both the upper and the lower surface extend 

 far in front of the first vertebra of the back, and thus a large part (more than 

 a third) of the neck is inclosed within the walls of the body. The carapace 

 and plastron are joined from the arch of the second to that of the fifth pair 

 of ribs. The bridge on each side, reaching down from the outer edge to the 

 flattened loAver surface, is necessarily long, and the openings about the ends of 

 the body for the protrusion of the head and limbs and tail are high and large. 

 The bridges reach considerably inward in descending ; their free edges are turned 

 far into the body, and the upper edge is united by long sutures with the 

 second and fifth ribs. The plastron vmderlies the whole broad flattened lower 

 surface of the body ; its free edges project little beyond their attachment, in fact 

 not at all, except about the front end, so that the plastron does not protect, as 

 is the case in the Emydoidte, any extensive part of the lower surfiice beyond that 

 to which it is actually attached. The free edges of the carapace jDroject rather 

 widely over the legs, but little behind the pelvis, and only slightly over the neck. 



^ The effects produced in the outline of the tion of the shield, as they do not constitute an essen- 

 outer surface by the varying thickness of the derm tial element of the form, but are rather an incidental 

 are omitted here, and noted below in the descrip- structural result of it. 



