844 MESSES. HANCOCK AND HOWSE 



Dr. Geinitz has also incorrectly classified this fish with the Ces- 

 tracionts ; but, by the observations made in a former paper, it 

 will be seen that we agree with Professor Agassiz in placing 

 Janassa among the Rays. 



We now, after these introductory remarks, proceed to give a 

 general description of the oral armature of this curious fish, and 

 in conclusion a special description of the several specimens ob- 

 tained by Mr. Dufi". 



The dental apparatus of Janassa hituviinosa is very peculiar ; 

 it cannot, however, be distinguished generically from that of the 

 so-called Climaxodus lingumformis, Atthey, the Coal-Measure re- 

 presentative of Miinster's genus; and for a comparison of the 

 two we would refer to the previous paper on the subject, pub- 

 lished in the November number of the " Annals."* 



The teeth of the fish now before us, like those of the Coal- 

 Measure species, are of two kinds, primary and secondary, the 

 latter being petalodontoid in form. The largest of the primary, 

 including the root, are 1\ inch long, and half an inch wide ; they 

 are elongated, somewhat depressed, ovate, tapering a little pos- 

 teriorly, and have the surface divided into two well-marked 

 portions — an anterior scoop-like cutting-margin, and a posterior 

 ridged crushing- surface or disk, with a long depressed root ex- 

 tending backwards (PI. X., figs. 2, 4, 5). The scoop-like cut- 

 ting-margin is considerably more than one-fourth the entire 

 length of the crown : it projects upwards and forwards, and 

 is smooth and concave, with the edge usually obtuse and arched 

 or a little sinuous from wear, but when comparatively fresh is 

 pretty regularly arched, and when quite perfect is probably den- 

 ticulated, if we may judge from the small lateral teeth. The 

 crushing surface or disk is elongated, the sides being nearly 

 parallel, though tapering to a blunt point behind, the general 

 form resembling that of a lengthened shield. The surface is 

 convex, and is covered with about twenty close-set transverse 



* Hancock and Atthey, " On the Generic Identity of Climaxodus and Janassa.'' In the 

 figure of the restored row of teetli of the so-called Climaxodus linguxformis illustrating the 

 former paper, the under row is represented as in advance of the upper, purposely to indicate 

 its relation to the latter. But the specimen clearly demonstrates the fact that the tipper row 

 projects a little in advance of the under, as is the case in Janassa hituminosa. 



