GEOLOGICAL SURVEY OF THE TERRITORIES. 407 



tus and continued as a rounded ridge, separating the anterior and exter- 

 nal faces of the bone. Median posterior ridge not prominent. Centra of 

 dorsal vertebrae depressed. Humerus broad, short. 



Description : This species is represented by portions of cranium, as 

 post frontal, susparsorial, pterygoid articular, and quadrate bones ; by 

 parts or wholes of seven, vertebrae, which are all dorsals, and by 

 scapula and coracoid, with many elements of the fore limb. The latter 

 includes humerus, radius, a carpal, and numerous metacarpals and pha- 

 langes. 



The species is first well characterized by the form of the quadrate 

 bone. This element lacks a portion of the ala, and the postero-superior 

 decurved process, but is otherwise perfect. Its form is intermediate 

 between that in L. validus, Cope, and Mosasaurus depressas, Cope. Its 

 external angle of the proximal extremity is posterior to its usual posi- 

 tion, as in the former species, but is less prominent than in it. It ex- 

 tends to near the distal end, disappearing between the extremities of the 

 median posterior and the distal longitudinal angles. The former of 

 these is short and it disappears by a gradual descent distally, in a very 

 rugose margin. The distal longitudinal is short and acute, not promi- 

 nent at the distal extremity. From the posterior position of the prox- 

 imal external angle, the alar articular surface is somewhat elongate. 

 The postero-external face above the meatus is proportionately short. 

 The meatal pit is scarcely one-fifth the usual size, so far as determinable 

 from the present surface, but it is possible that the greater part is filled 

 by an impacted mass of bone derived from the adjacent ridge. The 

 margins of the articular extremities and of the ala are striate and papil- 

 lose rugose. No meatal knob. 



The suspensorium is slender. It is peculiar in the great extent of the 

 exoccipital element, which covers the whole superior surface, and ex- 

 tends externally over the opisthotic to the squamosal, concealing the 

 former, except its anterior margin. The prootic sends a small proximal 

 portion only to the superior face. 



The pterygoid has been free from its fellow medially. A distal and 

 median portions have been lost ; the remaining portions present bases 

 and alveolae for eleven teeth. The fangs are rugulose and but little 

 swollen ; probably five to seven stood on the lost portions. The bases 

 of the crowns are circular. The external process of the bone is slender 

 and flat. 



The portion of the mandible preserved includes much of the articu- 

 lar and adherent parts of the angular. The latter forms a narrow band 

 on the lower edge of the external face, and one twice as wide on the 

 inner face. The only characteristic feature is the lowness of the ridge, 

 which descends and extends anteriorly from the anterior margin of the 

 cotylus for the quadratum. 



Of the vertebrae several are so distorted by pressure as to be uncharac- 

 teristic. Two well-preserved anterior dorsals have transversely oval 

 articular surfaces excavated openly above for the neural canal. One is 

 from a position anterior to the other, and these surfaces are less oval, 

 though still transverse. The centra of both are very concave in profile 

 below, and expand both interiorly and laterally to the edge of the cup. 

 A deep groove surrounds the base of the posterior face. In the ante- 

 rior dorsal the neural arch is preserved. It exhibits an approach to 

 a zygosphen articulation more marked than in any other Liodon, and 

 is hence nearer Clidastes in this respect, as well as in the slender ptery- 

 goids. A zygosphen is not separated from the zygapophyses, owing to 

 their connection by a lamina of bone. The notches at the posterior end 



