86 0. C. Marsh—New Characters of Mosasauroid Reptiles. 
subrectangular shape of all the plates shows that when in 
position, the outer and inner diameters of the sclerotic ring were 
not widely different. 
nusensit 
Figures 2, 3, and 4.—Sclerotic plates of Lestosaurus simus, Marsh; natural size, 
external view. 
The sclerotic plates of the Mosasauroids may be distinguished 
from the dermal scutes on the head and body by their peculiar — 
shape, and much larger size. The latter, so far as known, are 
more rhombic in form, but their variations on different parts _ 
of the body, and in different species, remain to be determined. 
Tue TRANSVERSE Bone. 
ears ee, 
transverse bone, and Owen, the ectopterygoid, has not been 
observed hitherto in the Mosasauroids, but it is present 10 
both points he was in error. true palatines are small a 
edentulous bones, in front and outside of the pterygoids. They 
* Vertebrata of the Cretaceous, p. 118. a 
