A. Smith Woodward— On a Tooth of Oxyrhina. 



75 



again represented mineralogically by the fornaation of albite and 

 probably other soda-bearing felspars. 



The transfer has been disputed by some observers, but the evidence 

 is too strong to be denied, even if it may be proved that there are 

 exceptions. It has also been suggested that the transfer has not 

 taken place at the time of intrusion, — that it is not a contact- 

 phenomenon at all,— but is due to later processes connected with 

 the decay of the igneous rock. This is a point still calling for 

 investigation. 



I hope later on to deal with the subject of these basic contacts, as 

 I am at present engaged in examining a large series of such rocks. 



All that I need here remark is that I have fully satisfied myself 

 of the transfer of soda, and of the presence in some cases of large 

 amounts of isotropic material due to contact-action. 



XV. — Note on a Tooth op Oxyrhina from the Eed Crag of 



Suffolk. 

 By Arthur Smith Woodward, F.L.S., F.G.S. 



ALL the Selachian teeth hitherto obtained from the English 

 Crags referable to the genus Oxyrhina are much compressed 

 antero-posteriorly, and are thus slender in proportion to their size. 

 They are now commonly regarded as representing a single extinct 

 species, Oxyrhina hastalis of Agassiz/ and the same form of dentition 



Tooth of Oxyrhina cransa, Ag., natiu-al size, from the external (A) and lateral 



(B) aspects ; Eed Crag, Hemley Hall, near Woodbridge, Suffolk. 



[Collection of T. W. Eeader, Esq., F.G.S.] 



is abundant in the Pliocene of Italy, besides occurring in other Tertiary 



deposits in various parts of the world. In Italy and Belgium, how- 



evei", these comparatively slender teeth are accompanied by a few 



1 Smith Woodward, "Catal. Foss. Fishes, B. M.," pt. i. p. 385 ; E. T. Newton, 

 " Verteb. Pliocene Dep. Britain" (Mem. Geol. Surv. 1891), p. 106, pi. ix. fig. 15. 



