Fossil FisJi Remains. 63 



Observations. — As in the case of tlio Diddon presently to Ije 

 described, we are also fortunate in havinp; so complete a series 

 of these fish remains, and although we lack many completely 

 preserved specimens, there is a large number of fragmentary 

 specimens, and these have materially assisted in the ehicidation 

 of their characters as a whole. In all, we have examined about 

 35 examples of this form. Judging by the general characters 

 shown in the previously illustrated examples of F-daphodon teeth, 

 our forms show some slight divergences from typical specimens 

 ill the number and arrangement of the tritors, apparently mak- 

 ing an approach towards Chimsera.* The recorded range of 

 Edaphodon is Cretaceous to Oligooene. It does not appear to 

 have been noted before as occurring in the rocks of the southern 

 hemisphere. 



Comparing our fossils with specimens of Edaphodon in our 

 Museum from British localities, and with various descriptions 

 and figures available for our purpose, the nearest ally appears 

 to be Edaphodon bucklandi, Agassiz''^ from the British Eocene ; 

 but this species is a larger form, is more heavily built, and the 

 tritors have a coarser structure. 



Genus /si'/iyodus, Egerton. 

 Ischyodus mortoni, sp. nov. (Plate YI., Fig. 6.) 



Description. — The specimen to which we append the above 

 name is part of a left mandibular tooth having a very elongate 

 and robust character, and with a remarkable concavity towards 

 the upper j^art in the posterior region. The extreme anterior 

 portion of the tooth is missing, but the posterior is fairly com- 

 plete, showing part of the smooth superficial bonj' layer of the 

 posterior margin. This marginal layer is marked by a series of 

 slightly undularting thread-like ridges, which are most distinct 

 on the inner third of the i^urface, a stronger ridge marking off 

 this area. It is, moreover, convexly rounded off where it meets 



1 Compare diafrrains in Smith Woodward Cat. I'oss. Fishes (Brit. Mus.), pt. ii. 

 1891, p. u4. 



•2 Poiss. Foss., vol. iii., 1843, p. 351, pi. .\1., a, figs. 1-4, 9-12, 19-24 ; also E. eurvsrna- 

 thus, Ajf., Dixon, Koss. Sussex, 18.50, p. Ill, pi. x., figs. IS, 19, 22, pi. xii., f. 5. 



