194 PROF. OWEN ON A THERIODONT REPTILE 
size, equality, and even ranking of the molar series had not more 
decisively demonstrated the Theriodont character of the fossils. 
It might, indeed, be objected that the evidence of the size and 
shape of the teeth in Titanosuchus is partial or defective; and I 
admit that the indications of the molar series, like those of the 
canine and incisor teeth, are of the implanted fangs. The shapes 
of their respective crowns are matters of inference from analogy ; 
but the closest analogy in the reptilian series is with the Theriodont 
group. 
Lycosaurus pardalis* exemplifies a similar proportion of molars 
as compared with incisors. Galeosaurus planiceps; shows the uni- 
form character and straight alveolar supporting frame of the molar 
series. 
Tt is reasonable to infer that the crowns of this series, in Titano- 
suchus, would show a less disproportionate size than might be de- 
duced from the roots. But these, with the alveolar frames enclosing 
them, afford sufficient evidence of the absence of that repetition of 
the canine-like characters of shape and relative size in certain teeth 
of the series, which characters are associated with the undulatory 
course of the alveolar border of the jaw in true Crocodiles; while 
the earlier Teleosaurian type and its existing representative in the 
Gavials have no teeth recognizable by differential shapes or sizes as 
incisors and canines from the series of equable and similarly shaped 
teeth supported by their long and slender jaws. 
I have, however, finally to refer to another Thericdont character, 
which, with the humeral onet, exemplifies a nearer affinity to the 
carnivorous Mammalia than is recognizable in any known modifica- 
tion of the Crocodilian order. 
If, for example, a vertical section be made of the tooth of a Cro- 
codile answering to the canine in 7%tanosuchus, its root does not 
contract or solidify as it descends in the socket, but it ends in an 
open basis of the hollow cone, whose apex terminates the more solid 
crown of the tooth. Communicating with the inner side of the 
socket is a larger or smaller reserve socket lodging the matrix of the 
successional tooth. 
Every Crocodilian tooth shows more or less of this character, 
associated with the relatively shorter duration of the teeth in use 
and their speedy shedding and replacement by successional teeth. 
In the Theriodontia the teeth, at least in full-grown specimens, 
are longer retained and develop roots, which contract as they sink 
in the socket and become more or less closed at the implanted end, 
like the permanent teeth in diphyodont Mammalia. 
In a portion of the right maxillary of Titanosuchus containing the 
implanted root of the canine, this was exposed by chiselling away 
the socket to the end of the root, which gradually contracted from 
a breadth of 14 inch (40 millims.) to that of 25 millims., when 
the fang rounded off to terminate obtusely. The external wall of 
the pulp-cavity of the canine had been in part broken away in the 
* Op. cit. p. 15, pl. xiv. fig. 2. t Jb. p. 23, pl. xviii. 
{ Quart, Journ. Geol. Soc, yol, xxxii. p. 96, pl. xi. fig. 6, h, &. 
