16 THE PROCEEDINUS OF THE LINNEAN SOCIETY 



two species. Dr. Gunther, I observe (Ann. and Mag. Nat. Hist. 

 Series 3, vol. 20, p. 53), describes D. calligastra as having no 

 loreal ; but what I take to be the loreal shield in that species is of 

 remarkable length. 



The scales of the back are in thirteen rows, all elongate except- 

 ing the central and external ones. The abdominal plates are 

 strongly bicarinated, making the central half of each quite flat ; 

 this double ridge or keel is stronger than in the other two species 

 and extends to the very tip of the tail. 



The entire upper surface is of an olive black, the under surface 

 is yellowish white, clouded more or less with black according to 

 the age of the individual, the young specimens being much darker 

 than the adult. In the specimen before you, which, though full 

 grown, is probably not an old one, the first thirty or forty abdomi- 

 nal plates are without any black marking whatever, the next 100 

 plates or so are only slightly marked on each side near the ventral 

 ridges, but every plate getting distinctly darker as you descend. 

 The remainder are nearly black with their posterior edges, and a 

 broad vitta outside of each ventral ridge white. The subcaudal 

 plates have each a black patch at its point of contact with its 

 opposite plate, presenting the appearance of a continuous black 

 line of lozenge-shaped markings along the entire length of the 

 tail. The upper labial shields are white, with the exception of 

 the eighth and the upper portion of some of the others. The 

 lower portion of the rostral shield is also white. 



