WILLISTON: RANGE AND DISTRIBUTION OF THE MOSASAURS. 183 
avoid the suspicion that both the specimens in question and those 
described by the high authority just mentioned (Owen) really ap- 
pertain to the dorsal series of MWosasaurus.” The vertebre figured 
by Leidy seem to be congeneric with the Kansas forms referred to 
7ylosaurus, but, inasmuch the genus is distinguished with difficulty 
by the vertebra alone, it would be hazardous to say with any degree 
of certainty that they are really the same. Cope, in 1870 (Extinct 
Batrachia, etc.), referred certain bones to this same species under 
the name Zzodon. Inthe plates of the same work he figured two 
or three vertebra over the name of Z. validus, referred to L. levis 
in the text, and to Céidastes antivalidus in the explanation of the 
plates! The bone figured in the text certainly does not belong 
with 7Zylosaurus, and, if Cope is correct in his determination, 
Macrosaurus is not the same as 7losaurus. The different names 
that he used, however, are sufficient evidence of his uncertainty. 
Lesticodus was given by Leidy to a species (ZL. /mpav) represented 
by teeth and portions of the jaws, and was afterwards abandoned 
by him. Cope apparently believed that the genus was the same as 
Liodon Cope. 
Nectoportheus Cope was based upon Liodon validus (olim 
Macrosaurus) and was characterized by him as follows: (Extinct 
Batrachia, etc,, 208) ‘‘The posterior dorsals are so much more 
depressed than in Zéodon devis, that future discovery may justify 
the generic separation of the genus Wectoportheus, which I originally 
applied to this animal.” In his ‘‘Cretaceous Vertebrata” (p. 160) 
he says: ‘‘The typical species of this genus (Léodon anceps Owen) 
is very little known, but few remains having been obtained from 
the English chalk, its locality and horizon. Numerous North 
American species resemble it in the forms of the crown of the 
teeth, and it is probable, though uncertain, that they agree in other 
respects also. Several names have been proposed for our species, 
the earliest of which is MZacrosaurus Owen. This name applies to 
species with compressed dorsal vertebre, as 7. /evis and ZL. 
Mitchel’, both from the New Jersey Greensand. Tor species with 
the depressed dorsal vertebre, as 1. validus from New Jersey, LZ. 
perlatus from New Jersey, and Z. proriger from Kansas, the name 
Nectoportheus was proposed and briefly characterized.” 
The definition of 7vlosaurus (Rhinosaurus) was explicit and exact, 
leaving no doubt of the genus to which it was intended to apply. 
PLATECARPUS. 
? Holcodus Gibbes, Smithsonian Contributions, 1, p. 9, 1850. 
Platecarpus Cope, Boston Soc Naty Hast? ¢coo/spucrOd. 
