EXPLANATION OF PLATE XXV.
Discussion.
The President remarked that, according to observations which he had lately made, rocks appeared often to suffer contemporaneous erosion, frequently being broken up into small fragments and redeposited.
Prof. Boyd Dawkins was of opinion that the Ichthyosaurus belonged 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 Sphærodus 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 connexion 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. Hulke 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 I. enthekiodon from the Kimmeridge Clay. However, on the point of age he would express no opinion.
Mr. Charlesworth, remembering how opinion had changed on the subject of Trigonia, did not see why an Ichthyosaurus might not have survived to the Tertiary period. Caution, however, was necessary; 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. P. Jones expressed his gratitude for the information given by Prof. Leith Adams in his paper on the Mastodon of Malta,
