Mr. W. King on the Tetrabranchiate Cephalopoda. 279 



Notes connected with the Synoptical Table. 



I have drawn up the foregoing Table without having seen that 

 which accompanies Agassiz's paper : the translation in Professor 

 Jamieson's Journal is all that I have seen at present. 



It must be understood, that I offer this classification of the Tetra- 

 branchiate Cephalopods only as an approximate one. It is for the 

 principles of such a classification that I contend. The genera Ortho~ 

 cerus, Ceratites and Goniatites have been carried up into the Jurassic 

 epoch, because they have been found in the St. Cassian (Tyrol) beds, 

 associated with Ammonites and other fossils of this age. 



If the Ceratites are of the epoch mentioned in the last note, and the 

 Ammonites did not exist previously, it follows that the latter must 

 be connected with the former, as represented in the Table. 



I confess that I have little faith respecting the Ammonites having 

 died out at the close of the secondary period. In the case of many 

 species and genera we find, that although they have ceased to exist 

 in our own seas, they are still to be found living in other latitudes : 

 this fact leads me to think, that the Ammonites may have lived 

 within the tropics during the deposition of the early tertiary beds 

 of France and England. In making this remark, I have in view the 

 Ammonidians of Pondicherry and other places in India. 



The generic difference between the Russian Goniatites ? and 



Ceratites nodosus is so trifling, as to cause me to think that the last 

 genus will yet be found as low down as the Permian or the Carbo- 

 niferous series. Fossils undoubtedly form a good character by which 

 to enable the geologist to decide as to the age of a rock ; but it ought 

 always to be borne in mind, that unless the relative position of such 

 a rock to others whose general character is known can be fairly 

 made out, the organic test should be received with due caution. 



I have placed the Scaphites in connexion with the Cretaceous 

 Ammonites ; it is probable however that they existed previously 

 to the latter. There is a Jurassic species of Ammonites (I do not 

 know the specific name at present) which becomes contracted and 

 irregular as it advances in age ; perhaps it stands in the same relation 

 to the true Scaphites as the Jurassic Turrilites Valdani does to the 

 true Turrilites of the Chalk. 



The Table will show that 1 differ from D'Archiac and De Verneuil 

 as regards Nautilus sipho and N. ziczac being Clymenias (Trans. 

 Geol. Soc. vol. vi. p. 328) ; and from Buckland and others respecting 

 these lobed species forming the link between the Ammonites and 

 the Nautiluses. The way in which I have spoken of the Discuses 

 in the lecture would imply that I consider them to form the ori- 

 ginal type of the Tetrabranchiate Cephalopods : it seems preferable 

 to wait until we know more of the early fauna of our planet before 

 any positive opinion is hazarded on this point. 



