DESCRIPTIONS OF FOSSIL LIZARDS GILMORE 21 



greater in other parts of the animal, since scattered scutes found 

 with other specimens show this smooth band to be one-fourth the 

 total length of the scute. 



The exposed surfaces of all the scutes are thickly studded with 

 rounded tubercles. Those on the margins are usually arranged in 

 two or more concentric rows. The tubercles inside these outer rows 

 are usuall}^ smaller and without definite arrangement, except that 

 there is a tendency in some scutes to form subcircular rows around 

 the low nodelike carina that occurs on the posterior dorsal surface. 

 Except on the median dorsal row the carina is always placed nearer 

 to the inner than to the outer side of the scute. This fact would 

 enable one to segregate scattered scutes into the right and left series. 



The ventral scutes have the same rectangular shape, but they are 

 distinguished from those described above by their smaller size, absence 

 of a carina, and less prominently developed tubercles without def- 

 inite arrangement. Since the anteriormost rows of the ventral 

 scutes preserved cover the posterior end of the ramus, it seems quite 

 probable that in life they continued farther forward under the jaws. 



The scutes of the median dorsal row differ from the others in being 

 wedge-shaped, wider in front than behind, and the low nodelike 

 carina centrally placed on the posterior half. Slight disarrange- 

 ment renders the count a little uncertain, but there appear to be 14r 

 longitudinal rows of scutes, enumerating from the median dorsal 

 row to the midventral region. This would indicate the complete cir- 

 cumference as being composed of 29 longitudinal rows of plates at a 

 point inmiediately posterior to the skull. 



With the discovery of more and better-preserved specimens, it be- 

 comes more and more apparent that in the genus Glyptosaurus the 

 tubercular patterns on the scutes are of little assistance in taxonomy. 

 Such differences as have been used in the past are found to be value- 

 less from the fact that this ornamentation varies with the position 

 of the scute on the body. Therefore until their limitations are known 

 they will be of little use in characterizing species. 



The cranial scutes, on the other hand, appear to show definite dif- 

 ferences, although, as indicated by the two specimens now before 

 me, there is considerable individual variation that must be always 

 taken into consideration. 



Genus PELTOSAURUS Cope 



PELTOSAURUS species 



In 1928 I referred ^ three incomplete dentaries from the Fort 

 Union, Paleocene of Montana, to the genus Peltosaurus^ but without 



• Mem. Nat. Acad. Sci., vol. 22, p. 137, 1928. 



