482 Prof. Owen — On Two New Ichthyodorulites. 



are few in number compared with most similarly barbed fossU. fish- 

 spines; four project from about one third of the length of the 

 body of the spine, and not more than seven are traceable in the 

 present specimen. The ganoin, which enamels that body, terminates 

 as usual below in an oblique line descending from the dentate 

 border to the thick convex border or fore part of the spine. The 

 implanted base is also, as usual, smooth and finely striated lengthwise. 



The length of the spine, as here preserved, is 2 inches ; but 

 adding the wanting point according to the indications of the rate of 

 contraction, and from the impression in the counterpart leaf of coal- 

 shale, the entire length would be 2^ inches ; the greatest breadth is 

 three lines ; the thickness at that part is f line. 



The soft plastic state of the carbonaceous oose in which this 

 weapon, with probably the fish that bore it, sunk, and ultimately 

 settled, is shown by the exquisitely beautiful impression of the 

 ornamentation of the glittering blade which the hardened coal now 

 retains. 



Fig. A, side view of Lepracanthus Colei, nat. size. B, magnified 

 view of part of the ganoin. 



Hyhodus complanatus, Ow. — This spine rests in a block of stone, 

 from the Iguanodon-quarry of Mr. Bensted, at Maidstone, of the 

 Neocomian or Greensand period, the latest, I believe, in which any 

 evidence of the genus Hyhodus has been detected. The sides are 

 flatter, and join the thick hinder border at a less open angle than in 

 most other Hybodont spines. 



The sides are longitudinally ridged, but with less regularity and 

 with more variety in the size of the ridges, than in any other Eyhodi. 

 At the summit they are fine and close set, but they slightly increase 

 in thickness toward the front margin ; they recede from each other 

 as the spine expands and descends : the finer ridges at the hinder 

 half of the side continue close- set along the upper half of the spine, 

 and also for one third of the breadth of the side next the inner con- 

 cave border. The thicker ridges at the lower half of the enamelled 

 body, are reduced to three or four in number, separated by a smooth 

 tract, along the middle third of the side, from the finer ridges : the 

 coarser ridges near the front border become reduced to two along 

 the basal fourth of the enamelled body, with a wide smooth 

 or unridged interval between them and the finer ridges. The 

 anterior border is narrow, but obtuse. Along the middle of the 

 broad flattened hinder border, a series of short strong recurved 

 denticles arms the very low or open angle at which the halves of 

 the hinder border meet; there are about thirty denticles along this 

 angle : they are thick, triangular, two lines across the base, nearly 

 three lines in length, pointed. The enamelled body of this spine is 

 slightly recurved. 



From Hyhodus reticidatus (and from Hyhodus curtus, which is the 

 second shorter spine of H. reticulatiis),^ the present species differs in 



^ This fact is shown in the rare specimen with teeth, integument, and both spines 

 of Hybodus reticulatiis in the Museum at Florence Court, where Agasstz recognised 

 his Hybodus curtus in the second smaller spine, on his last visit to Ireland. 



