ON PISSIL FISH-TEETH. 299 



mouth (the left, according to our supposition) and only three to the 

 other side : while of the flatter group, which we suppose to be lower 

 jaw specimens, seven belong to the same side, or the left side, and only 

 one to the right. 



If our supposition as to the position of these teeth in the jaws of the 

 animal be correct, (and a similar idea was previously thrown out by 

 Quenstedt) an examination of Agassiz's figures seems to' shew that he had 

 only six teeth belonging to the right jaw, of which only two were upper- 

 jaw teeth, and four were lower, while he had eight teeth of the left jaw 

 of which all were lower-jaw teeth. At present, these Indian specimens 

 throw no light on these very curious facts ; but they appear to confirm 

 very strongly the doubts which have more than once been thrown on the 

 correctness of Agassiz's supposition that there had been only one tooth on 

 each side of each jaw. 



Mr. Edmund Higglns, writing in 1853* stated that his collection of 

 Ceratodus teeth at that time amounted to about 140 varieties — and 

 that among this large number he could scarcely say that he ever met 

 with a duplicate ! We believe his collection has now extended to nearly 

 200 varieties with the same result ! 



No spines have been as yet found in these rocks in India, and we are 

 not therefore able to throw any light whatever on the suggestion of 

 Agassiz that the spines, called by him Nemacanthus, beloncred to the 

 same genus as the. teeth to which he gave the generic name Ceratodus. 



We do not intend to assert in the following descriptions that the 

 varieties to which we have given names are really distinct species. It is 

 simply useful to distinguish such well marked varieties for future re- 

 ference. It is highly probable that some of them may prove identical 

 with others found in Europe, but not yet figured or described. Mr. 

 Higgins, as cited above, gives 2 1 names as of distinct species, but un- 

 fortunately no descriptions or figures accompany this list. 



* Morris' Catalogue of British Fossils, 2nd Edition, page 320. 



