Cope. ] 42 {Mareh 8, 
but one, an anterior, cutting edge, the posterior face being regularly 
convex. The inner face is much more convex than the outer, and the 
flatness of the latter is marked at the apex of the tooth by a short ridge 
which bounds it posteriorly. This is a trace of the bounding angle which 
extends to the basis of the crown in Mosasaurus. The anterior cutting 
edge is in profile convex ; the posterior outline concave to near the tip. 
The cutting edge is acute, and beautifully ribbed on each side, but not 
properly denticulate. The surface of the tooth is not facetted, but the 
outer face exhibits the peculiarity of a longitudinal coneavity, or shallow 
groove extending from the base to the middle of the crown. The enamel 
is polished, but under the microscope minutely and extensively striate: 
ridged. This description is taken from the second or third from the 
anterior end of the maxillary bone. The third from the distal end of the 
dentary is very similar. 
The crowns become rapidly more compressed as we pass backwards. 
From a broad oval section of two crown bases, we reach a flattened oval 
crown, with the cutting edge sharp behind as well as before, and minutely 
ribbed. ‘The crown is not facetted, and is more convex interiorly than 
exteriorly. The exterior convexity is chiefly anterior ; the posterior face 
is slightly concave from the open groove already described as present in 
the anterior teeth. In two posterior crowns, one still more elongate in 
section, the external concavity becomes flatter and includes a great 
part of the outer face. A tooth still more posterior presents the peculiarity 
of the species in the strongest light. The crown is still more compressed, 
directed backwards, and only .25 higher than wide antero-posteriorly at 
the base. The latter is a little over twice the transverse diameter just 
behind the middle. The surface presents the characters described in 
others. The outer concave surface is wide and shallow, and contributes 
to the attenuation of the posterior half of the tooth rather than the an- 
terior, which is consequently thicker. The cutting edges are sharp, the 
anterior convex and retreating backwards to the rather obtuse apex ; the 
posterior convex above, concave below. 
The exposed parts of the dental pedestals are frustra of cones, neither 
swollen nor concave. 
Measurements. M. 
Third superior maxillary length crown............0.++-++ 0.088 
 Neiglt.crown and pedestal... ii. .ausc.ss i.e. >. . .048 
‘¢ longitudinal diameter base crown...... WA cage 002 
Hee SUPSMAVOLEOn cis wee: OU fo ee ee .018 
Sixth dentary, longitudinal ....... Pog oe Pi cre ce 0rd! 
Mi ss transverse... .... ait aehiye Pont eRe A sires ote eed 
Eleventh dentary height crown..............+. bite ide 034 
us height crown. and pedestal. ..06. «ive cee seen s .0505 
fs longitudinal diameter basis crown............... .026 
#3 UPADBYCIEG . 06.665 6 oe wVviele or Vale he caes Gee eas 014 
The articular bone is perhaps .66 the size of that of Mosasaurus dekayt 
I I Y 
