728 



DR R. H. TRAQUAIR ON 



anterior or oral margin, which is also the longest, is, however, not quite straight, as it 

 shows a very obtuse angle in the middle ; the two lateral margins are shorter and 

 slightly convergent posteriorly ; the postero-lateral margins follow, each at an obtuse 

 angle to its respective lateral one, and they meet each other behind, also at an obtuse 

 angle, which fits into the anterior notch or excavation of the plate next to be described. 

 This, the great median ventral plate (m.v.), is of a broadly oval form, having a widely 

 open notch or indentation in front, which, as aforesaid, receives the posterior angle of 

 the mental plate. In the specimen shown in PL III., and of which text fig. 2 is a 

 sketch, the hinder extremity of this plate is broken off, but in fig. 3 I have restored its 

 contour from other specimens, among others that represented in PL V. fig. 1. It will 



pv.2. 



Fig. 2. — Sketch of a specimen of the carapace of Drepanaapis Gemurulcnensis, Schl. One-third natural size. 

 o., mouth; r. , rostral or upper labial plates; e.l. , external labial plate ; to., mental plate ; a.v.l., anterior 

 ventro-lateral ; m.v., median ventral; m.d., portion of inner surface of median dorsal; p. v. I., posterior 

 ventrolateral ; p.l., postero-lateral or cornual plate. 



therefore be seen that the posterior border of this plate presents a narrow bluntly- 

 rounded median notch or indentation, the direction of which is continued for a little 

 way in front by a longitudinal fold-like elevation of the surface. To this indentation I 

 shall again refer in speaking of the scales of the caudal region. 



Returning now to the front, we find on each margin of the carapace, immediately 

 behind the small external labial plate, another and rather larger element of a trapezoidal 

 shape (x.) ; transversely placed, with a short external margin, a longer internal one, 

 while the posterior is the largest, and is directed nearly at a right angle to the middle 

 line of the creature. This plate is seen in situ on both sides of the carapace in 

 PL III., that of the left side in PL IV., while in PL II. that of the right side is seen 

 detached from its place and turned round so as to show its sculptured surface. In PL I. 



