32 
the diseased condition of this bone at the centre of the dental magazine. 
An injury in life has caused a swelling of the bone on the external side and 
development of a deep pit without tooth rows forward of the centre of the 
tooth series. That this injury altered the normal proportions of the 
edentulous portion is, of course, very improbable. 
Comparative Measurements of Dentaries 
Paratype? of 
Stephano- 
saurus 
marginatus, 
No. 361, 
G.S.C. 
Skull first 
referred to 
S. marginatus, 
No. 351, 
G.S.C. 
Skull last 
referred to 
S. marginatus, 
No. 2869, 
G.S.C. 
Mm. 
Mm. 
Mm. 
Length of dentary from posterior tooth to tip 
489 
432 
400 
Length of dental magazine 
320+ 
315 
272 
Length from most anterior dental foramen to tip of 
dentary 
172 
133+ 
140 
Length (longitudinally) of 10 tooth rows, 12 to 21 in- 
clusive 
81 
85 
84 
Average length of nonfunctional teeth in above rows. 
28 
35 
36 
Number of vertical tooth rows in dentary 
45 or 46 
40 
41 
Examination of the above comparative table demonstrates conclusively 
that the dentary included by Lambe in the description of Stephanosaurus 
( Trachodon ) marginatus pertains to a different animal than do the dentaries 
belonging to the subsequently referred skulls. That the fundamental 
differences observed are outside the range of variation within a species 
appears to be shown by the close agreement of the two referred specimens 
that represent individuals of somewhat different age and size, but agree 
so closely in their important details as to leave no doubt that they belong 
to the same genus and species. The greater number of vertical tooth rows; 
the shorter and narrower proportions of the individual nonfunctional 
teeth; the longer, narrower, and apparently less abruptly decurved eden- 
tulous-symphysial portion of the typical dentary are features that together 
appear sufficient to indicate its distinctness from those specimens sub- 
sequently referred to it. 
This critical examination of the type materials of Stephanosaurus 
( Trachodon ) marginatus Lambe, may now be summed up as follows: The 
“remains of one individual” is, I believe, determinate, and, therefore, 
obviously remains the primary type. The proportions of the fore limb 
bones show that it cannot pertain to the Lambeosaurinse. The maxilla, 
which could only by the most liberal interpretation be considered a para- 
type, is also excluded from that sub-family. Likewise, the dentary is 
shown to be in all probability generically and specifically distinct from 
the subsequently referred skulls, which clearly pertain to the Lambeosau- 
rinse. The question now arises, can the remains of “one individual” which 
consist, as originally enumerated by Lambe 1 , of the “humerus, ulna, and 
radius of the left fore limb, a metatarsal and phalanges of the pes, the 
»Op. cit., 1902, p. 71. 
