22 
uniform curvature along the inferior margin, Cuvier has adduced 
the same structure as distinctive of the Monitors, Iguanas, and other 
true saurian reptiles, so that whatever support these modifications of 
structure may give to the question respecting the marsupial nature 
of the Stonesfield fossils, as compared with other groups of mammals, 
they do not affect the previous question of their mammiferous na- 
ture, as compared with reptiles and fishes. ‘The fossil jaws, Mr. 
Ogilby says, agree with those of mammals, and differ from those of 
all recent reptiles, in not being prolonged backward behind the 
articulating condyle ; a character in conjunction with the former 
relation, which would be, in this author’s opinion, well nigh incon- 
trovertible, if it were absolutely exclusive ; but the extinct saurians, 
the Pterodactyles, Ichthyosaurt, and Plesiosauri, cotemporaries of the 
Stonesfield fossils, differ from their recent congeners in this respect 
and agree with mammals. Mr. Ogilby is of opinion that the con- 
dyle is round both in D. Prevostii and D. Bucklandii, and is there- 
fore a very strong point in favour of the mammiferous nature 
of the jaws. ‘The angular process, he says, is distinct in one speci- 
men of D. Prevostii, and, though broken eff in the other, has left a 
well-defined impression ; but that it agrees in position with the insec- 
tivora, and not the marsupialia, being situated in the plane passing 
through the coronoid process and the ramus of the jaw. In the 
D. Bucklandii, he conceives, the process is entirely wanting; but 
that there is a slight longitudinal ridge partially broken, which 
might be mistaken for it, though placed at a considerable distance up 
the jaw, or nearly on a level with the condyle, and not at the 
inferior angular rim of the jaw. He is therefore of opinion that the 
D. Bucklandii cannot be properly associated either with the marsu- 
pial or insectivorous mammals. ‘The composition of the teeth, he 
conceives, cannot be advanced successfully against the mammiferous 
nature of the fossils, because animal matter preponderates over 
mineral in the teeth of the great majority of the Insectivorous Cheir- 
optera, as well as in those of the Myrmecobius, and other small marsu- 
pials. In the jaw of the D. Prevostii, Mr. Ogilby cannot perceive 
any appearance of a dentary canal, the fangs of the teeth, in his 
opinion, almost reaching the inferior margin of the jaw, and being 
implanted completely in the bone; but in the D. Bucklandit, he has 
observed, towards the anterior extremity of the jaw, a hollow 
space filled with foreign matter, and very like a dentary canal. The 
double fangs of the teeth of D. Prevostii, and probably of D. Buck- 
landi, he says, are strong points of agreement between the fossils 
and mammifers in general; but that double roots necessarily indi- 
cate, not the mammiferous nature of the animal, but the compound 
form of the crowns of the teeth. 
2. With respect to the most prominent characters by which the 
Stonesfield fossils are distinguished from recent mammals of the 
insectivorous and marsupial families, Mr. Ogilby mentioned, first, 
the position of the condyle, which is placed in the fossil jaws ina line 
rather below the level of the crowns of the teeth; and he stated 
that the condyle not being elevated above the line in the Dasyurus 
