23'i Illinois State Laboratory of Natural History. 



plates with slight longitudinal rugae. First and last dorsal 

 plates with obsolete ruga?. The remaining dorsal plates and 

 the marginals smooth. Nuchal plate nearly twice as long as 

 wide, its anterior edge straight. First dorsal plate vase-shaped 

 in outline. The second and third dorsal plates are equal in 

 size, are elongate, quadrangular, and about equally wide at 

 both ends. The fourth dorsal plate is about equal in size to 

 the two preceding plates and is elongate, but is hexagonal and 

 narrowed behind. The fifth is the widest plate of the series, 

 being about a third wider than long, and is sub-heptagonal. 

 First costal plate triangular in general form, with its outer 

 margin rounded. The remaining costal plates are quadran- 

 gular, and decrease in relative size from before backwards. 

 Anterior lateral angles of gular plates bluntly rounded. Pos- 

 terior lobe of plastron with a median notch behind: on each 

 side of the notch slightly sinuate. Inguinal plate produced 

 forwards so as to exclude the greater part of the abdominal 

 from the marginal plates. Head of medium size. Superior 

 jaw with a perfectly smooth edge and a very slight median 

 notch. Edge of lower jaw distinctly serrated and with a prom- 

 inent median tooth; its outer surface roughened. Alveolar 

 surfaces of jaws wide, with strongly toothed ridges. Feet 

 completely webbed, with rather strong, slightly curved claws. 

 Blackish above, obsoletely reticulate with yellow lines, the 

 areas between these lines being occupied in most cases by nar- 

 row, concentric lines of the same color. The lines on the 

 dorsal })lates are mostly longitudinal; those on the sides are 

 mostly transverse. On the marginal plates are sets of concen- 

 tric yellow lines, each set with two more or less evident 

 central dots, one on each side of the line of union of two mar- 

 ginal plates. Wider orange-red lines lie one across the middle 

 of each marginal plate; they expand at the margin of the shell 

 and bifurcate near the inner edges of the marginal plates, their 

 branches uniting with each other or with the netted lines of 

 the upper part of the surface. Plastron pale straw-yellow, 

 without blotches; wings of the pectoral and abdominal plates 

 each with two parallel dusky lines. Inguinal plate with a 

 dusky ring. Marginal plates beneath orange-red, with large 

 round dusky spots at the union of two plates, including in 



