THE GEOLOGIST. 



JULY 1863. 



ON A NEW SPECIES OF HYBODUS FROM THE LOWER 



CHALK. 



By S. J. Mackie, F.G.S. 



Since the publication of Agassiz' ' Poissons Fossiles ' only one addi- 

 tion, that we are aware of, has been made to our knowledge of this 

 interesting genus of fishes, — certainly, at least, in respect to British 

 geology. In 184-5 Sir Philip Egerton described, before the Geological 

 Society, a large jaw, or rather mouth of teeth, of a fish of this kind, 

 found by Captain Ibbetson in the Isle of Wight, and named by Sit 

 Philip Ili/hod us bassnnus. 



This species has been assigned to the Lower Greensand, in Morris's 

 Catalogue, but the bed seems, from Sir Philip's statement, to be in a 

 dubious position, for he speaks of it only as " near the junction of the 

 Lower Greensand and Wealden," and says the specimen was sent to 

 him " in the hopes it might tend to show to which of the two forma- 

 tions its bed should be assigned," — a question he further declines to 

 answer, as " the evidence it affords on this question is neither direct 

 nor conclusive, inasmuch as it is an undescribed species ; and conse- 

 quently any deductions beyond those based upon general affinities 

 would be unwarrantable." Sir Philip adds, however, further on : 

 "The geological inferences afforded by the specimen are briefly told. 

 The species is new. The genus is undoubtedly Uybodus. This genus 

 attains its maximum expansion in the Oolitic series, but it ranges 

 from the Musehelkalk to the Chalk inclusive. The only evidence of its 

 occurrence in the latter formation is a fragment of an ichthyodorulite 



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