1865.] LANKESTER CRAG MAMMALIA. 227 



from various Crag pits. 4. Large fragments from Felixstow, in 

 the author's cabinet. To this list I may now add two fine frag- 

 ments, which I lately observed in the collection of my friend Mr. 

 Packard, of Westerfield. 



When travelling in Belgium last summer, I was much gratified 

 by finding a large portion of one of these tusks in the collection 

 of Professor Van Beneden, of Louvain. This specimen, which is 

 unique, was not obtained from the " Crag superieur " or " Crag 

 jaune," which is the exact equivalent of our Red Crag, but was 

 met with in the " Crag moyen " or " Crag gris," an older and weU- 

 defined deposit, abounding in unrolled remains of Cetaceans and 

 Sharks, as well as MoUuscan fossils. Professor Van Beneden had 

 been unable at this time to decide the affinities of the animal to 

 which this tooth belonged ; but since then he has communicated his 

 opinion to me in a letter, that it was closely allied to the Walrus — 

 a conclusion at which I had previously arrived. The grounds upon 

 which this conclusion is founded will now be given. 



General Form and Outline. — The majority of the specimens of the 

 tusk which have been obtained are its pointed terminations ; but 

 other specimens, of the base and intermediate portions, have come to 

 light. Throughout its length, which in some examples must have 

 been fully three feet, the tusk is slightly curved; but in those which 

 appear to be fully grown the curve is considerably greater towards 

 the terminal point, the direction of the curve probably giving the 

 tusk, if its Pinnigrade affinities be established, a retrofiected posi- 

 tion, as in the Dinotherium. The Crag tusk is very much com- 

 pressed laterally, so that its transverse section has an elliptical out- 

 line, whilst that of the D mother ium-tu&k is nearly circular. The 

 amount of lateral compression is, however, extremely variable, as it 

 is also in the living Walruses ; the amount also of the lateral as well 

 as the antero-posterior flection of the tusk appears to vary, as in 

 the recent Trichecus, the variability of which in the size and form 

 of its tusks is well known. A single large furrow on the outer 

 surface, two on the inner, and one on the inner curved margin, ex- 

 tend along the whole length of the tusk in many specimens, exactly 

 similar to those noticed on some tusks of Walrus ; but in both the 

 recent and fossil specimens they are subject to much variation, in 

 their major or minor development. No appearance of any wearing 

 of the point of the tusks by use during hfe is observable ; and indeed 

 the greater backward curvature of that part seems to result from its 

 freedom from usage, since in the Walrus the point of the tusk is 

 rapidly worn away, which of course checks any tendency to curvatm-e 

 which might become apparent if the tusk were not used against such 

 hard substances as rocks and blocks of ice (PL X. figs. 1-3). 



From an examination of the general contour and form of the 

 tusks, without regard to their substance or structure, one Avould 

 unquestionably be led to regard them as belonging to an animal 

 similar to the existing Walrus, inasmuch as it is in this animal 

 alone that this form of tusk, with its longitudinal furrows, great 

 length, and gentle curvature, is found. 



