from the Marl- Slate of Midderidge. 51 



" The specimen shown (Dyas, tab. 5. f. 1) widens out at the 

 back of the head on each side in an arched, triang-ular, wing- 

 sliaped, blunt process [cc)^ which may represent the cross bone 

 {os transversaJe). 



^^ Byzenos latipinnatus^ Miinster, 1843 (Beitr. vi. tab. 1. f. 2, 

 p. 50), from the Knpferschiefer of Richelsdorf, is a fragment 

 covered with fine shagreen, but which does not admit of a 

 perfect description, and which miglit just as well be referred 

 to J. hituminosa as to any other genus of fish." 



With the above remarks we entirely concur, excepting the 

 statement that the teeth of Janassa are palatal, as it is proved, 

 by their relationship to Myliohates^ that they are true jaw- 

 teeth. The other remark that does not appear to us satisfac- 

 tory is, that the two bodies designated by Count Miinster ear- 

 bones are considered by Dr. Geinitz to be teeth placed near 

 the entrance of tlie throat. The specimens from our locality 

 do not show a trace of these peculiar bodies ; but we are dis- 

 posed to consider them casts of a pair of cranial cavities rather 

 than teeth. That they are not teeth seems to be clearly indi- 

 cated by the entire absence of enamel covering, as pointed out 

 by Count IMiinster. Dr. Geinitz has also incorrectly classified 

 this fish with the Cestracionts ; 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 descrijJtion of the several speci- 

 mens obtained by Mr. Duif. 



The dental apparatus oi Janassa hituminosa is very peculiar; 

 it cannot, however, be distinguished generically from that of 

 the so-called Climaxodus linguaformis^ Atthey, the Coal- 

 measure representative of Mlinster's genus ; and for a com- 

 parison of the two we would refer to the previous paper on 

 the subject, published 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 pri- 

 mary, including the root, are \\ inch long and \ inch wide ; 



* Hancock and Atthey, " On the Generic Tdentity of Climaxodus and 

 Janassa."' In the figure of the restored row of teeth of the so-called Cli- 

 maxodus linffU(pfort7iis illustrating the former paper, the under row is re- 

 presented as in advance of the upper, purposely to ijidicate its relation to 

 the latter. But the specimen clearly demonstrates the fact that tlie upper 

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

 hituminosa. 



4* 



