1865.] LANKESTER — CRAG MAMMALIA. 231 



my much-valued friend Professor Huxley, whose name has already 

 been associated with the history of the Crag Mammalia by his recent 

 researches on Ziphioid Cetaceans. 



It appears that the Tricliecodon Huxleyi, like the Cetacean re- 

 mains of the Crag and large Sharks' teeth alluded to in the first 

 part of this paper, is a derived fossil in the Eed Crag, belonging 

 properly to the Middle Crag, which is not now observable in this 

 country, but is well developed at and near Antwerp. 



III. The probable Identity of the Teeth op the so-caxled BAiiE- 



NODON PHYSALOIDES WITH THOSE OF SpECIES OF THE GeNEEA BeLEM- 

 NOZIPHITJS AND SaXTALODON. 



The Cetacean teeth which occur in great numbers in the Eed 

 Crag, of large size and more or less conical shape, are at present 

 in this country referred to the Balcenodon physaloides of Professor 

 Owen (PI. XI. figs. 3 & 5). From a comparison of many hundreds 

 of specimens in various collections, I have ascertained that there are 

 two forms of these teeth — those which simply taper more or less 

 towards the crown and have large bases, and those which have a 

 more elongated base and a nipple-shaped crown coated with enamel 

 (PI. XI. figs. 6 & 7). To the first form belongs the original specimen 

 figured as Balcenodon physaloides in the ' British Possil Mammalia,' 

 whilst the second form, which is most obviously and clearly distin- 

 guished from the first in specimens which are only slightly rolled, 

 is entirely distinct. The excavations which have now for some 

 years been going on at Antwerp, have furnished most abundant and 

 beautiful remains of a fossil Cetacean fauna from the Middle Crag. 

 The teeth of the lower jaws of the Ziphioids have been identified, 

 and the remains of the remarkable Cetacean Squalodon have been 

 obtained in very fine preservation. M. Van Beneden, who has had 

 the charge of all the Mammalian remains obtained, and whose re- 

 searches on the subject are well known, assures me, from a com- 

 parison with the Antwerp fossils of specimens which I sent to 

 Louvain, that the Balcenodon teeth of the first form (that originally 

 described) are without doubt the teeth of the bident lower jaws of 

 those Ziphioids whose remains occur with them in the Red Crag ; 

 whilst the more elongated teeth with an emarginated nipple-like 

 crown of enamel, more or less worn, are the teeth of a species of 

 Squalodon, probably the Scqualodon Antwerpiense, the restoration and 

 description of which by MM. Van Beneden and Gervais are well 

 known. 



If this be the case — and the amount of material afforded to M. 

 Van Beneden by the workings at Antwerp is of so perfect and satis- 

 factory a nature that there can be little doubt on the matter — the 

 Balcenodon physaloides will have to be removed from the list of our 

 British fossil Mammals, and species oiZiphius and Scquahdon adopted 

 in its place. 



