39 



CISTUDA BLA^BINGII.—Holbrook. 



Cpiate III. 



/ Characters. Head moderate, upper jaw emarginate in front, lower jaw with 

 ' a small hook; shell sub-round, elongated, smooth, ecarinate, with an entire 



margin; sternum entire in front, deeply emarginate behind, bivalvular, posterior 



valve but slightly larger. 



Description. The head is rather small, smooth above, and slightly pointed at 

 the snout; the nostrils are anterior, and closely approximated; the eyes are large 

 and prominent, the pupil black, the iris light grey. The upper jaw is broad, the 

 cutting edge sharp and deeply emarginate in front; the lower is strong and firm, 

 and furnished with a small hook. The neck is long and slightly contracted at 

 the back of the head. 



The shell is oblong, rounded, very nearly as broad before as behind, smooth 

 and ecarinate, with an ientire margin. Of the vertebral plates, the anterior is 

 broad, pentagonal, with two of its articulating surfaces directed forwards and 

 outwards, and meeting at an angle in front; the second and third are very 

 regularly hexagonal, broadest in the transverse direction — the former very 

 slightly concave in front, and the latter as slightly concave behind; the fourth is 

 regularly heptagonal, rather concave posteriorly; the fifth is octagonal, smaller 

 above and larger below. The anterior lateral plate is irregularly quadrilateral, 

 larger and rounded below, smaller and straight above; the second and third are 

 pentagonal; the fourth is smaller and quadrilateral. There are twenty-five 

 marginal plates, making an entire cutting border; the intermediate or nuchal is 



