ON CLIMAXODUS AND JANASSA. 337 



three ridges, with the grooves very wide ; the scoop-Hke cutting- 

 margin is deep, oblique, and projects laterally on the concave 

 side. 



The largest Petalodontoid or secondary teeth are nearly fths 

 of an inch wide and f ths of an inch long : they are inequilateral 

 and oblique with one side concave, the other convex ; they are 

 depressed, and the crown is somewhat longer than the root ; 

 the former consists principally of a wide, sharp, hollow, scoop- 

 like cutting-margin, which in fresh specimens is obscurely den- 

 ticulated ; the grinding- surface is very short, and is represented 

 by only two transverse close-set delicate ridges immediately be- 

 low the cutting-margin ; the root tapers a little backwards, and 

 is truncate. 



From the character of the teeth above described, it may be 

 inferred that the food of Climaxodus was composed of some soft 

 material, notwithstanding the rather formidable appearance of 

 the grinding or crushing-surface. The cutting-edge of the scoop- 

 like margin is sharp and thin, and does not seem calculated to 

 seize hard and resistant bodies ; and though it is frequently worn 

 evenly down, its sharpness is maintained, often, apparently, by 

 the wearing of the outside, as though the teeth had been over- 

 lapped by those that opposed them. And, moreover, the edge 

 is not broken or chipped, as might be expected if it had rough 

 work to perform, or came into contact with bony or shelly bodies. 

 Neither are the ridges of the crushing- surface broken, but worn 

 regularly, retaining their sharpness, though in a few instances 

 they are much reduced in height, as if they might even ulti- 

 mately by long use entirely disappear. 



At present only three species of Janassa are known, namely, 

 J. hituminosa, Schlotheim, from the Magnesian Limetone ; Cli- 

 maxodus imbricatus, M'Coy, from the Mountain Limestone ; and 

 C Unguceformis, Atthey, from the Coal-Measures. Two species 

 have been described by Mr. T. P. Barkas, under the respective 

 names of C. ovatiis'''' and C. veriniformis.\ The first is merely 

 the variety with comparatively smooth ridges ; the second is 

 the true C. Imr/ucB/ormis, which latter was the name first used. 



* Geological Magazine, Vol. V., p. 495. + Ibid, Vol. VI,, p. 381. 



