216 $. VII. DELINEATIONS 



SPECIMINA 

 Formarum fortuitarum. 



a. Sp. complanaturn sceleti, pinna pect. vent. 



caudaeque manifestos. 



b. Sp. sceleti,, pinnis omnibus carens. 



c. Sp. frustulis cxternarum corporis 



partium sceleto adhasrentibus. Petrificatum 

 trammutatum. 



Substantiarum. 



1. Sp. ex spato calcario et bitumine *(* composi- 

 turn, matrice continuata marges indurata? 

 schistose?. 



ICHTHYOLITHUS sagittidens. 



ICHTHlf OL. dentis Squali, cuspidati ancipitis, 

 margine integerrimo, radice bifurca subgibbosa 

 sursum bidenticulata. S. t. 



f In the Rev. Mr. Gradon's excellent account of the fossil fish 

 of Monte Bolca (v. Trans. 11. 1. Acad, above referred to) he ob- 

 serves, that all parts of these reliquia, except some of the grosser 

 bones consisting of calcareous spar, are composed of a dark- 

 brown, hard, brittle, and somewhat glossy substance, which he 

 concludes to be the actual dry remains of the animals themselves, 

 preserved or embalmed, as it were, by the calcareous matter of 

 the matrix. We have not had an opportunity of examining many 

 specimens of these fossils; but in the few that have fallen under 

 our notice, the matter in question undoubtedly appeared to us, to 

 have been produced by the original substance of the fish repre- 

 sented; but under a complete change in the combination of its 

 elementary principles ; a perfect bitumen being the result, mixed 

 with a small proportion of calcareous earth. 



