agrees best with that, as well as the solid termination of the rostrum. But it is perhaps a legitimate question as to whether the forms of Choneziphius represented by Cuvier's first specimen, by his second, by the cast sent by Prof. Van Beneden to Paris of a third, by the small cast in the British Museum, and finally by this new Suffolk specimen are not all varieties of age and sex of one species. Hyperoodon is known to be exceedingly variable in the characters of the rostrum within the limits of the same species, and so perhaps were the fossil ziphioids. If this is not the case it is very strange that nearly every new specimen of a ziphioid rostrum which turns up baffles all attempts at finding its counterpart, and requires a new specific name. Choneziphius Pachardi stands certainly at one end of the series, the other extreme being represented by the small cast of Choneziphius in the British Museum. Woodcuts of Cuvier's Ziphius planirostris (fig. 1) and of Z. Cuvieri (fig. 2) are here given for the sake of comparison with the plate*.
I would direct the attention of those who are interested in the study of fossil Cetacea, and who have seen the Monograph of Crag Cetacea lately issued by the Palaeontographical Society, to a paper published by me in 1867 on the structure of the tooth of Micropteron Sowerbiense, in which I described the nipple -shaped tooth of Z. Layardi and Berardius Arnuxii, as well as that of the tooth specially treated of, and drew certain conclusions as to the character of recent and fossil ziphioid teeth, which are now set forth afresh, without reference to that paper, by Prof. Owen ; so, too, the views which I first advocated in this Journal as to the Diestien character of the Crag Cetacea are adopted without acknowledgment of any kind, though widely differing from Professor Owen's former views.
It should be remarked that the numerous sections of rostra given in the recent Monograph are purely imaginary, and that the separation of the bones marked 14 and 15 therein is hypothetical. Whilst no generic divisions of Ziphius are recognized, the specific name applied some years since by Prof. Huxley to a Belemnoziphius, namely " compressus," is taken by Professor Owen without any explanation, and applied as his own to another species. As a reply to assertions on the last page of the Monograph, I am glad to be able to mention here that I have obtained a Cetacean tooth of the Zeuglodont type from Suffolk. I mentioned its occurrence in the ' Geological Magazine ' (1868) ; it is probably one of the foliaceous molars of the Squalodon antverpiensis of Van Beneden and Gervais.
IV. The Trilophodont Mastodon of the Suffolk Bone-bed (Plate XXXIV. figs. 1-4).
In the 'Geological Magazine ' for 1869, I briefly noticed the occurrence of a trilophodont Mastodon in the Suffolk bone-bed, having observed an upper penultimate molar in the collection of Mr. Baker, of Woodbridge, which indicated such a form. This specimen is drawn
- I have to thank the authorities of the Palaeontographical Society for the
loan of these figures. — E. R. L.
2 o 2
