6Q 



MISCELLANEOUS. 



On some Dermal Tubercles associated ivith Fossil FisJi-remains. 

 To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, — In the ' Annals and Magazine of Natural History ' 

 for April, pp. 260 & 261, there is an interesting communication by 

 Messrs. Hancock and Atthey, in which they describe the discovery 

 of certain teeth-like bodies found associated with Cladodiis mirabilis 

 and Gyracanthus tuhercidatus. 



They refer to a paper of mine, published in the ' Transactions of 

 the Geological Society of Glasgow,' vol. iv. pt. 1. pp. 57-59, and 

 state that I seem to confound Diphdus with those teeth-like bodies 

 or dermal tubercles, and to consider the remains of the semicartila- 

 ginous skeleton to be shagreen, — and also state that it is to Prof. 

 Williamson that we owe the discovery of the true nature of this 

 peculiar substance, who clearly proves it to be the remains of what 

 he terms the chondriform bone or semicartilaginous skeleton. 



While I do not wish to call in question their deductions i-egarding 

 their own discoveries, or the identifications of Prof. Williamson, I 

 beg, however, to be allowed to express my surprise at those gentle- 

 men supposing that I had confounded Diplodus with the dermal 

 tubercles referred to. 



In my paper I refer to the discovery of a slab of ironstone covered 

 with shagreen, and two spines of Ctenacanthus hyhodoides imbedded 

 in that substance. Associated with these spines are a number of 

 the teeth of Cladodus mirabilis, aE. evidently in their proper relative 

 position. I had removed a portion of the ironstone overlying the 

 snout, and exposed the skin thickly studded over "with numerous 

 teeth-like bodies, consisting of two, three, and four curved diverging 

 points rising from an expanded base, and with a sharp keel on the 

 curved side passing to the apex of each of the points. 



Further on I state that I discovered on another slab of ironstone 

 the teeth of Diplodus i/ibbosits associated with another form of those 

 dermal teeth-like bodies ; but these are smooth, enamelled, circular 

 in section, and relatively larger, and more sharply pointed than 

 those with the keel along the curved face. Thus having found the 

 first form associated with the teeth of Cladodus mirabilis and the 

 latter with the teeth of Diplodus gibbosu^, and having frequently 

 verified this discovery, the conclusion was irresistible, viz. that 

 they each represented the dermal development of diff'erent fish ; 

 and as in the recent ray^s (that is, in the living forms) sexual dif- 

 ferences are to be noted in the dermal development, I suggested 

 the probability of the difference exhibited in the fossils being due to 

 a similar caiise. This suggestion is thrown out without the slightest 

 desire to dogmatize, well knowing that there have been far too many 

 forms named from being simply found associated with other parts. 

 The evidence, however, is much in favour of the suggestion. The 

 diff'erent forms are not only associated with, but arc imbedded in, 

 the shagreen of the fish. 



