102 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



very superficial characteristics, he manages to recog- 

 nize strange relationships which are disconcert- 

 ing to a naturalist. I shall confine^ myself to 

 quoting one of the most extraordinary of these 

 comparisons. The Conulary of the Silurian epoch, 

 with its conical shell similar to that of our existing 

 Pteropods, is regarded by Gaudry on account of 

 certain concave walls at the extremity of the shell 

 and notwithstanding the absence of any syphon, 

 as representing possibly the original form of the 

 Cephalopods. The curious molluscs of the family 

 of Chamacea, known by the name of Rudista on 

 account of their thick and rugged epidermis, are 

 considered by him as likely to have ancestral 

 relations with the rugged operculous Polyps, such 

 as the Calceola of the Devonian. 



Noticing Cephalopods with uncoiled shells, both 

 among the Nautilids of Primary times and among 

 the Ammonites of the Secondary, Gaudry does not 

 hesitate to frame the supposition, notwithstanding 

 the most fundamental differences of structure, that 

 " several forms of Nautilids have directly given 

 birth to the form of Ammonitidee which correspond 

 to them." In the same way the superficial resem- 

 blance of the phragmocone or partitioned part of the 

 shell of the Belemnites with the partitioned shell of the 

 Orthoceras of Primary times, inspires Gaudry with 

 the idea that these animals, different as they are 

 in organization, might be derived one from the other. 

 Finally, as to those curious Placoderm fishes of the 

 Silurian and the Devonian, so remarkable by their 

 cuirass of bony plates and yet deprived of all apparent 

 traces of ossified vertebral column, Gaudry sees 



