( 6 ) 



smaller thickness and deeper longitudinal grooves. Also Rai Lankesteb 

 is of opinion that in general they are bigger than those of the 

 walrus, although the maximum size of the two is (hesame. So these 

 tusks show a very good agreement with those of the Zealand fossil. 



The Belgian Trichechids, occurring in the "Crag" of' Antwerp, 

 have been described by P. J. van Beneden in a work of splendid 

 get up (26). The only pity is that the contents do not harmonise 

 at all with the exterior, since to a dangerous imagination more scope 

 has heen given than to accurate description and careful criticism. 

 When the fortifications round Antwerp were dug, fossil remains of 

 Pinnipedia were found in very differenl places and at different times : 

 they were treated by van Beneden in the following manner: 



"Voici, comment nous avons procédé: Après avoir réuni tons les 

 os de phoque, .... nous avons réuni tons les os de même nature 



c'esl a dire, les humerus, Ie- fémurs etc Après cette première 



operation nous avons reparti les os longs après leur taille, avant 

 devant nous les mèmes os des espèces vivantes. Si l'on considère, 

 que la plupart des pieces se répèle plusieurs fois, il n'est pas 

 difficile,.... d'établir parmi eux des groupes génériques et spéciiiques. 

 Quand cette operation est t'aite pour les os comme les humerus et 

 les fémurs,.... on leur rapporte les autres os, en se guidant d'abord 



d'après leur dimension Nous avons alors étalé les humerus, les 



fémurs, les vertèbres etc. des diverses espèces européennes et nous 

 nous sommes assures, de quelles espèces vivantes nos phoques fossiles 

 se rapprochent Ie plus. En répétant la même operation pour les 

 autre- os, nous sommes arrivés ainsi a composer nos espèces et a en 

 étalilir uu certain nombre avec une certitude entière." 



Hence when van Beneden had established a new species by means 

 of a single bone, he added to this bone what litted best in size, a 

 method which theoretically has some good points, but which in 

 practice, with the very incomplete Antwerp material, presents so 

 many difficulties, that the determinations of van Beneden must a 

 priori he received with some misgivings. In any case, only the first 

 piece of bone, on which a species was founded, may be regarded 

 as having been definitely determined: all the other bones, added to 

 it, must he critically re-examined. 



van Beneden describes three species of Trichechids, which he refers 

 to three genera. Of these Trichechus rosmarus is supposed to be 

 diluvial; the two others, Triehecodon Koninckii and Alachtherium 

 (Yet.-ii are tertiary. 



Of the common walrus only a scaphoid and an incomplete vertebra 

 are described : "qui out été quelque temps confondues .... avec les 



