336 Mr. A. S. Woodward on the 



Hemiaster nobilisj Dune. & Sladen. 

 Hemiaster gibhosus, A. Agassiz. 

 Hemiaster zonatus, A. Agassiz. 

 Hemiaster Bowerhanhi, Forbes. 

 Hemiaster Prestioichi^ Forbes. 

 Hemiaster digonus, d'Archiac. 

 Hemiaster elongatusj Dune. & Sladen. 

 Hemiaster carinatus, Dune. & Sladen. 

 Hemiaster cavernosus^ Phil. 



We have purposely omitted the subgenera Ahatus and 

 Tripylus. 



September 1888. 



XLIII. — On some Remains of the Extinct Selachian Astera- 

 canthus from the Oxford Clay of Peterhorough^ preserved in 

 the Collection of Alfred N. Leeds, Esq., of Eyebury. By 

 A. Smith Woodward, F.G.S., F.Z.S., of the British 

 Museum (Natural History). 



[Plate XII.] 



Since the elaborate researches of Agassiz it has always been 

 suspected that the dorsal fin-spines named Asteracanthus and 

 the teeth named Strophodus originally pertained to one and 

 the same fish ; but no proof of the circumstance has been 

 made known during the forty years that have elapsed since 

 the publication of the ' Poissons fossiles,' and one of the com- 

 monest of Mesozoic fossils has thus remained undetermined 

 among the miscellaneous group of " Ichthyodorulites." At 

 last, however, it is satisfactory to be able to bring forward 

 the requisite proof of this long-maintained surmise ; and not 

 only that, but also to make known some other important fea- 

 tures in the anatomy of Asteracanthus which definitely decide 

 its systematic position. Ample materials are furnished by 

 the fine series of fossils from the Oxford Clay of Fletton, near 

 Peterborough, in the collection of Alfred N. Leeds, Esq., of 

 Eyebury ; and I am indebted to the kindness of my friend 

 for the pleasurable opportunity of studying these interesting 

 specimens. 



