Ray Lankester, on the Tooth in Ziphius Sower biensis. 63 
the collection of Mr. Whincop, of Woodbridge. When cut 
longitudinally an appearance like that of “ pudding-stone ” (a 
simile used by Cuvier when describing the osteo-dentine of 
the walrus) was shown, accompanied with numerous longi- 
tudinal fissures. In PI. VI, fig. 4, a portion of this same body 
cur, transversely and mounted for microscopic examination is 
drawn. Figs. 5 and 6 represent two of the multiramose 
canals more highly magnified. No other structure than these 
bodies, and a homogeneous iron-stained matrix, could be made 
out. The claw-like fossil is very probably the osteo-dentinal 
core of a tooth of some one of the Rhynchoceti, the rostra of 
which are so abundant in the crag. 
Reduced to one half the natural size. 
The structure of the ziphioid tooth, as ascertained from 
the Micropteron Sowerbiensis, throws some light on the nature 
of the tooth called Balanodon, by Professor Owen. In a paper 
published in the f Quarterly Journal of the Geological Society/ 
1865, p. 231, I mentioned that Professor Van Beneden had 
obtained specimens from the Antwerp crag, which he identi- 
fies with our crag Balcenodon, and considers as ziphioid. The 
Balcenodon teeth, such as that drawn in fig. 2, are very much 
