530 A. L. ADAMS ON VERTEBRATA OF THE 
EXPLANATION OF PLATE XXV. 
Fig. 1. Fragment of a left ramus of a mandible of Phoca: nat. size. 
2, 2a, 26, 2c. Four teeth of Phoca rugasidens, Owen: nat. size. 
3 & 8a. Crown and profile views of a portion of a left maxilla of Halz- 
therium Schinzi ?, Kaup: nat. size. 
4, Crown view of a lower penultimate? molar of Halitheriwm Schinzi?, 
Kaup : nat. size. 
5 & 5a. Crown and profile of molar of Mastodon: nat. size. 
Discussion. 
The Prestpent remarked that, according to observations which 
he had lately made, rocks appeared often to suffer contempora- 
neous erosion, frequently being broken up into small fragments and 
redeposited. 
Prof. Boyp Dawxins was of opinion that the Ichthyosawrus be- 
longed to quite a different stage of evolution from that of the 
Miocene Mammalia. In illustration of the association of fossils with 
those of a different age, the Ichthyosaurus and Spherodus gigas in the 
Neocomian beds of Bedfordshire and Cambridge might be quoted, 
derived from the Kimmeridge Clay; and he thought there was no 
reason to believe that Ichthyosaurus lived in the Miocene period 
in Europe. The specimens mentioned in the paper were probably 
derived. 
Prof. Duncan thought that many of the fossils mentioned in con- 
nexion with the nodules were remaniés. As regards the age of the 
beds, his investigation of the corals had led him to the conclusion 
that they were Upper Miocene. He thought that the district bore 
evidence of subsidence. If the age of the upper deposits in Malta 
was Pliocene (as it might be), the whole might be connected with 
the upheaval of the Apennines. He thought Malta marked a point 
of near approach between the European and African continents. 
Mr. Hotxe stated that he had dealt with the Ichthyosaurus jaw 
from Malta simply as an anatomical question, not with reference to 
the deposits whence it had come. Still he must say it did not look 
worn, and the teeth were very like those of J. enthekiodon from the 
Kimmeridge Clay. However, on the point of age he would express 
no opinion. 
Mr. CuariLeswortH, remembering how opinion had changed on 
the subject of Trigonia, did not see why an Jchthyosaurus might not 
have survived to the Tertiary period. Caution, however, was neces- 
sary; for Cretaceous fossils were often found in the Pliocene, and 
it was often hard to say whether fossils were derivative or not. 
He argued, from his view of the nodules in the Crag and the Lias, 
that they were concretionary. He thought that, from the evidence 
before the Society, the species of Mastodon could not be determined. 
Prof. T. R. Jonzus expressed his gratitude for the information 
given by Prof. Leith Adams in his paper on the Mastodon of Malta, 
