224 ROYAL SOCIETY OF CANADA 
a small foramen is seen in the dentary, beneath the opening in the 
splenial and at the lower edge of the groove, leading into the dental 
canal (dc. plate I, fig. 1b and plate III, fig. 1c). ‘This canal passes 
forward, from the large cavity in the posterior half of the ramus, 
longitudinally through the dentary beneath the alveoli for the teeth. 
The splenial is applied closely to the dentary above and below the 
dentary groove. Mr. C. W. Gilmore in his able work on the “ Osteology 
of Baptanodon* (Marsh) ” refers to a similarly placed opening in the 
splenial of B. discus from the Jurassic of Wyoming.~ In describing 
the splenial Mr. Gilmore on p. 96 of his memoir says “ On the in- 
ternal surface, just posterior to the symphysis is an elongated oval 
Toramen that probably represents the internal mandibular foramen of 
the crocodile, though in this case it appears to be wholly enclosed by 
the splenial while in the crocodile the splenial only forms the anterior 
border.” In the mandible from Red Deer river the internal mandi- 
bular foramen is shown in its usual posterior position partly enclosed 
by the angular. A number of small foramina occur anteriorly in the 
upper surface of the dentary in an irregular line close to the alveoli 
on their inner side. The inner portion of the dentary behind the 
eighth tooth is missing but it appears to have enclosed the alveoli as 
far back as the thirteenth, judging from a portion of a dentary bone 
(cat. No. 780) that includes the sockets for the fifth tooth to the 
twelfth. Posterior to the thirteenth tooth the splenial probably formed 
the inner boundary of the alveoli. In the ramus under consideration 
the splenial has been broken away above from the eighth tooth back- 
ward but is partly preserved below as far back as the sixteenth. 
The other elements of the ramus preserved are the angular and 
the surangular. These two bones overlap each other to some extent, 
the thin vertical surangular’ passing down within the angular, the 
overlap immediately behind the external mandibular foramen amounting 
to 13 mm. Both the surangular and angular are imperfect anteriorly 
but in the former the upper posterior margin of the large exterior 
foramen is preserved (a, figs. 1 and 1a) whilst in the latter the lower 
posterior half of the small interior foramen is clearly shown (0, figs. 1 
and 1a). The surface of contact for the articular is seen on the inner 
posterior surface of the surangular. 
Exteriorly the ramus exhibits very rugose sculpture in its hinder 
half. Here the surface of the surangular from near its upper border 
to its junction with the angular is broken into an irregular network 
of ridges enclosing deep depressions and pits elongated horizontally. 

* Memoirs of the Carnegie Museum, Pittsburgh. Vol. 1, No. 2, 1905. 
