806 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 
are seen, asin L.aquilunguisand L. inerassatus,in the dentary bone on the 
inner side of the roots of the functional teeth. As these develop, they ap- 
pear to take position immediately below the crown of the old tooth, and 
grow vertically in its axis, finally displacing the latter in the manner so 
characteristic of the Crocodilia. 
The dentary bone is not deep, but is robust in the transverse direction. 
The external side is little convex in the vertical direction, and displays a 
‘smooth surface. A series of rather large foramina, rather closely 
placed, extends near the superior alveolar margin. The inner face of 
the dentary is divided into two subequal planes by a wide, open, longi- 
tudinal groove, which terminates at the posterior border of the symphysis. 
The surface is smooth. The symphysis is a short plane, oblique to the 
long axis of the dentary bone, and having the usual antero-superior 
oblique direction. It is short, and is characterized by its absolute 
smoothness. Near its anterior inner border, there is a large foramen. 
This reptile differs from the ZL. incrassatus from the Judith River beds 
of Montana in many respects :—(1) There is no tooth having the form of 
the canine of that species, 7. ¢., having the transverse greater than the 
longitudinal diameter, and the cutting edges opposite ; (2) the anterior 
edge is not carried to the middle of the inner side of the crown in the 
anterior tooth preserved; as to the ramus, (3) the groove of the inner 
side is much inferior in position in the Colorado animal; (4) there are 
no symphyseal rugosities, as in L. incrassatus; (5) the Pann is shallower 
and thicker. 
The species may then be named Lelaps trihedrodon, frow the form of 
the second tooth. 
Measurements. 
M. 
Depth of ramus at posterior extremity of speplyels ajaveyeibin asd o. Aviawh  alasmucsain Riera See's 0.090 
Width of ramus at the same point...--- .--. -2---- 22-2 eee eee eee ee eee ee eee 0.050 
Depth of ramus at sixth tooth ,.---------.-.----+-----+----- pina aac tetris 0.095 
Width of ramus at sixth tooth........-- we eee eee ee eee ee cree een cmenee o--- 0.045 
Depth of ramus at sixth tooth to the internal groove...--..-..-----< ----++ +--+ 0.050 
Length of portion of ramus supporting nine teeth......--..-..---.----------+- 0.260 
Diameter of base of erown of fourth t00th snteropenteior svosevceecccn 0 
Total length of third tooth ........---- --- +--+ + 2-2 eee ee ec eee eee neces 0.145 
Diameter of base of crown of third tooth } Ma RETR toy INOS a tees pee 
antero-posterior --...-.--..------- 0.022 
Width: of anterior (Convex) face... .2 veceasidengiseicice cows wees ett eee nccsis 0.017 
Length of crown of second tooth .... 2.222. 224 seen ee cee cee ee cee eee eee ee 0.045 
Widthiof Tn nertace cio. see ke eeienkeeecedc eee Bae AS aeesnisae ewe eee 0.019 
Width of exterior face’... 2.22222 cee cece cece cece cece cere ceeece cece ecsssees 0.020 
Widthuofan terior faces. 0c2 se net sis ackseeeei pest omens Geraci ses iscsi 0.012 
In this connection, I may mention that Prof. O. C. Marsh, of New 
Haven, has recently created another synonym by renaming the genus 
Lelaps. This is done on the supposition that the latter name is pre- 
occupied in entomology. The name has been used in that science, it is 
true, but simply as a synonym, and was therefore not employed or occu- 
pied when I applied it to this genus of extinct reptiles. 
