PUZZLES AND PATRIARCHS. 201 



by which they are traversed. These it is sup- 

 posed represent sense-organs. Behind the head, 

 it will be noted, are a pair of jointed append- 

 ages, whose origin is problematical. They pro- 

 bably served the purpose of fins, but they do not 

 seem to have been derived in the same way. 

 These fin-like structures are further remarkable 

 on account of the fact that they were hollow, 

 thus recalling the tubular limbs of invertebrates, 

 with which, however, they of course have nothing 

 to do. 



How long these forms will remain "bones of 

 contention " we of course cannot say, but there 

 are signs that the veil is lifting. Dr Traquair is 

 of opinion that both the Heterostraci and Osteo- 

 straci are rightly to be regarded as forming one 

 sub-class Ostracodermi. Furthermore, recent 

 researches of his have succeeded in establishing 

 a connection between these and certain exceed- 

 ingly interesting and puzzling forms known as 

 the Ccdolepidce. 



The Coelolepidse are extremely ancient shark- 

 like fishes of the Devonian age. The name they 

 bear is bestowed on account of the fact the scales 

 are hollow. These hollow scales or rather spines, 

 were shagreen-like in general form, but were open 

 below, and without the basal plate seen in the 

 typical shagreen-forming scale. The form of 

 the tail was shark-like. Bat as yet no traces 

 of jaws, teeth, eyes, gill-slits or internal skele- 

 ton have been discovered. The peculiar nature 

 of the external covering leads Dr Traquair to 

 believe that these curious and ancient creatures 

 derive their origin from the same stock as 



