180 Dr Hibbert on the Limestone of Bnrdiehouse 



from any other circumstance, to infer that certain of the minute 

 animals thus described are referable to the Cypris, the prosecution 

 of this research cannot be more safely conducted than in still 

 confining our attention to the recent family of the Cypridea, for 

 the detection, if possible, of other forms belonging to animals pre- 

 sumed to be of common habits. Another form, for instance, rather 

 approaches to that of the Daphnia than the Cypris. But if, in- 

 stead of an external crust, we could arrive at the knowledge of 

 an internal organization, it is not improbable that the entomos- 

 traca thus compared might prove to be different animals altoge- 

 ther. 



It is for this reason that I would name the animal repre- 



■ ^ — . -^ sented in the three different views of the annex- 



vM*^ ^22^ ^» ed Avood-cut, by the cautious name of Daphnoidia 



c rather than Daphnia ; indicative of an individual 



approaching to the recent Daphnia. 



The shell of the Daphnia, like that of the Daphnoidia of 

 Burdiehouse, is not described as exactly bivalve, but as subuni- 

 valve, opening longitudinally on one side only of the encased 

 animal. This character may, I think, be plainly detected in the 

 instance of the fossil example. I shall not venture upon assign- 

 ing to it a specific name, until I am better assured with regard 

 to its proper generic character. 



Other minute animals possess shells of extreme tenuity, too 

 many of which appear in a crushed and broken state. In this 

 form they exhibit a sort of spiral organization by no means unlike 

 that of the Planorbis or Spirorbis, to which they were referred 

 by an eminent conchologist, whose opinion regarding them I 

 consulted. But, upon a renewed examination of certain of these 

 remains, which, owing to an infiltration of calcareous matter, 

 have had their forms tolerably well preserved, I am now inclined 

 to place some doubt upon the judgment which had been passed 

 upon their character. 



The external form of one animal most resembles that of the 



