ANNIVERSARY ADDRESS OF THE PRESIDENT. evil 
marl, and containing freshwater shells of the genera Planorbis, 
Valvata, Cyclas, and others identical with species now inhabiting 
the same region. Dr. Wyman, in his excellent paper, has pointed 
out that the Casteroides is a large extinct rodent, having greater ana- 
logies in its osteology to the Castors than to any other living genus. 
Its relation to the Capybara Hydrocherus, the largest of living 
rodents, which it exceeded in size, is also alluded to, and the dif- 
ferences in its teeth carefully described. It is also shown to present 
some analogies with the genus Fiber, as well as with Castor and 
Hydrocherus. 
The discovery of the entire cranium of the Zeuglodon was an- 
nounced in the course of last year by Mr. Tuomey, State Geologist 
of South Carolina, and a figure of it was published in the American 
Journal of Science, September 1847. It was discovered by Messrs. 
Holmes and Gibbes in the eocene beds of the Ashley river, about 
ten miles from Charleston. Mr. Tuomey observed that the double 
occipital condyle showed it to have been a mammal, while the squa- 
mous sutures have a symmetrical form, and refer it to the Cetacea, to 
which Prof. Owen first pomted out its relations. These conclusions 
are the more important, because they differ from those deduced by 
Dr. Carus from the imperfect skeleton of the Zeuglodon, submitted 
to him by Mr. Koch, and of which he has lately published a detailed 
description with plates. A full and complete notice of this singular 
fossil has just appeared in the form of a monograph on the genus 
Basilosaurus or Zeuglodon by Prof. L. R. Gibbes, who has shown 
that there are two species of the genus. 
In regard to the geological position of the Zeuglodon, you have 
learnt from Mr. Lyell’s paper on the so-called nummulitic limestone 
of Alabama, above-mentioned, that it occurs in one of the mem- 
bers of the Eocene group in all the places where he met with the 
bones. He has since informed me that the analogy of the whole 
group of tertiary shells, with which it is more immediately connected 
in the localities examined by him, leads him to infer that it belongs 
to that middle division of the Eocene which in Mr. Prestwich’s 
paper is called the Bracklesham beds. 
Various additions to our knowledge of fossil mammals have been 
made by M. Pomel, who has among other labours described a new 
genus of fossil pachyderms, approaching the hippopotamus, under 
the name Hlotherium. To one of the communications by the same 
author, it may be desirable especially to call attention more in detail, 
inasmuch as it refers to the life upon, and physical conditions of a 
particular locality at a highly interesting geological period. This 
memoir relates to the fossil flora and fauna of the pisolitic forma- 
tion, a name given to certain deposits in the Paris tertiary district, 
of a concretionary form, occurring between the plastic clay and the 
chalk, and which M. Elie de Beaumont, upon purely geological data, 
refers to the highest portion of the cretaceous series. M. Pomel 
points out that the observations of M. Desor show this formation 
not to be accidental, but to be clearly equivalent both geologically and 
paleeontologically to the highest chalk of the Pays Bas. 
