Ixiv. PRESIDENT'S ADDRESS. ' 



palatal tooth of Stropliodus magnus, belonging to the family 

 Cestraciontidce, a shark furnished with powerful crushing teeth ; 

 the species is founded upon detached teeth, not yet correlated with 

 dorsal fin-spines. It has been suggested that the spines known 

 under the name of Asteracantlms belong to this shark, but 

 absolute proof is as yet wanting. The teeth of Stropliodus are 

 quadrate and elongate, the extremities slanting downwards, and 

 often slightly curved. Isolated teeth are not unfrequently met vvith 

 in the Oolites (reticulatus, magnus subreticulatus, Ag.) A complete 

 inferior jaw with four rows of teeth is described by the late Sir 

 Richard Owen (Geol. Mag. 1869) from the Great Oolite of Caen, 

 Normandy. Mr. G. M. Hansel has several of these palatal teeth 

 from the Forest Marble of the neighbouring parish of Puncknowle. 

 I have been unable to find in works of Mineralogy any notice of 

 Lapis Judaicus, which Hutchins so graphically describes. 

 Stropliodus has an extensive vertical range from the Permian to the 

 Chalk inclusive. The Oxford and Kimmeridge Clays yield the 

 well-marked form, S. reticulatus. The Cretaceous series contains 

 the last traces of the genus as far as is as now known, one from the 

 Greensand of Maidstone, the other from the Chalk. 



THE RONTGEN RAYS. 



Rontgen, Professor of Physics at Wurtemburg University, 

 discovered that a number of substances which are opaque to 

 visible rays of light are transparent to certain waves, capable of 

 affecting a photographic plate, and that the new actinic rays can 

 pass through them. Among other appliances an apparatus has 

 been invented consisting of a black cardboard tube enclosed at 

 one end with a disc of the same material, coated internally with a 

 fluorescent substance. At the other end is placed a lens, and the 

 object to be observed is viewed through a Crookes' tube. The 

 parts not influenced by the Rontgen rays are delineated in 

 shadow. Already the discovery has been successfully applied 

 in medicine and surgery. Numerous surgical cases of fractured 

 bones have been examined with satisfactory results. One 





