40 FOSSIL TURTLES OF NORTH AMERICA. 
trals joining extensively at the midline. Bridge about twice as broad as long. Inframarginals 
almost wholly on the plastral bones. Plastron with hinder lobe not shortened and not notcht 
behind. Pelvis not suturally articulated with the plastral bones. Skull pointed anteriorly; 
most of its surface bones finely tuberculated. Bones of lower jaw smooth; the symphysis 
short. 
This genus was establisht by Professor Marsh in the year 18go (Amer. Jour. 
Scl., XL, p. 177), his type being G. ornatus, collected in the Upper Jurassic of 
Wivontne: This species is apparently identical with Cope’s Compsemys plic atulus. 
A comparison of specimens of Compsemys victus Leidy with Cope’ S species just 
mentioned makes it certain that the two forms are not congeneric. Compsemys 
plicatulus must therefore be removed from Compsem ysya and Marsh’s genus Gl yptops 
becomes available. The eas ie by Cope of various species oe Jurassic and 
Cretaceous turtles to Compsemys was evidently due principally to supposed resem- 
blances inthe sculpture; but all of these species, except the type, C. victa, must be 
referred to other genera. ‘There are no evidences that C. victa possest mesoplas- 
tra. The total absence of distal prolongations of the costals for insertion in the 
peripherals of C. victa and their presence in G. plicatulus sufficiently separate them 
generically. 
To Gly ptops is provisionally referred G. pervicax, which in some respects 
approaches more closely Pleurosternon, more especially in having the plastron 
slightly notcht behind. On the other hand, the bridge is longer than in Glyptops 
plicatulus. It is not improbable that it represents an undescribed genus. 
It is to be noted that usually when authors have referred to the genus Compsemys 
they have had in mind the species C. Cane ae because its Ghercrer: were well 
known through Professor Marsh’s and Dr. Baur’s descriptions; whereas, little is 
even now known about C. victa. For these references the writer’s Bibliography and 
Catalogue of the Fossil Vertebrata of North America, 1902, p. 437, may be consulted. 
As here employed, G/yptops will include 4 species: the type, G. plicatulus of the 
Jurassic, G. celatus of the Lower Cretaceous, G. pervicax of the Benton, and 
G. depressus of the uppermost Cretaceous. Possibly when more is known of the two 
last-mentioned species they will be removed from the genus. 
Glyptops is closely related to Pleurosternon Oxtn as already recognized by 
Dr. Baur. However, it differs from the latter in having the hinder lobe of the 
plastron less constricted and without posterior notch, in having the inframarginals 
almost wholly on the plastral bones, in having the costo- marginal sulci well below 
the costo-peripheral sutures, except over the bridges, and in having longer bridges. 
The distance from a line joining the free border oF the anterior iene of che plastron 
with the posterior lobe to the outer end of the mesoplastron is contained in the width 
of the bridge about three times in Plewrosternon and about two times in Glyptops. 
Heloc hel ys i is another relative of Glyptops. Its hinder plastral lobe is little more 
than half as long as wide; the plastron appears to have been less closely joined to 
the carapace than in Glyptops; the bridges are short; and the last neural, the only 
one known, 1s hexagonal, with the broader end directed backward. 
KrY To THE KNowN SPECIES. 
7. Jurassic. 
a. Morrison beds : plicatulus 
4A. Cretaceous. 
a. Lower Cretaceous. 
b. Potomac beds : calatus 
bb. Benton beds Lt ; pervicax 
aa, Upper Cretaceous. 
c. Denver beds? depressus 
