KANSAS UNIVERSITY QUARTERLY. 
Wo. VIT. JULY, 1808. Now 3; 
Individual Variations in the Genus 
| Xiphactinus Leidy” 
Contributions from the Paleontological Laboratory, No. 31. 
BY ALBAN STEWART. 
With Plates VII, VIII, LX, X. 
The exceptionally fine collection of X7phactinus material in the 
Kansas University museum has suggested a series of comparisons 
which show that the individual variations within the species are 
both numerous and interesting. My attention was first called to 
these facts by finding certain individuals which I could not place 
in any of the known species from America with any degree of 
satisfaction, and yet the differences were not sufflcient to be called 
specific. The comparisons are confined entirely to the jaws, and 
show differences in size, shape, and arrangement of the teeth that 
are very marked, and | think prove conclusively that these charac- 
ters can not be regarded as specific in the two species involved. 
For convenience to those who may wish to examine the material 
in the future, the catalogue numbers on the cuts of the specimens 
will be used in reference to each individual in this article. As the 
relation of X. molossus and X. thaumas are most affected by this 
discussion, the original description of the jaws as given by 
Cope,+ will be partially repeated here in order to have the specific 
characters of these parts well in mind. 
*Xiphactinus audax Leidy (Proc. Acad. Nat. Sci., Phila., 1870, p. 12) has been shown 
to be a synonym of Sauwrocephalus Cope (U. 8. Geol. Surv., Wyoming, etc., 1872, p. 418). 
In a letter to Prof. Mudge, dated October 28, 1870, which will shortly be published in 
the fourth volume of the Kansas University Geological Survey, Cope refers it to 
Saurocephalus thaumas (Portheus thawmas Cope). After carefully comparing the de- 
seription and figure of the pectoralspine of X. audaxr I was led to the same conclusion; 
and as the genus Portheus was not made known by Cope until 1871 (Proc. Am. Phil. Soc., 
1871, p. 173), according to the rules of nomenclature Niphactinus should have priority, 
+Cret. Vert., 194-95. 
(115) KAN. UNIV. QUAR., VOL. VII, NO. 3, JULY, 1898, SERIES A. 
