THE JURASSIC PERIOD. 241 



to note the occurrence of the oldest known fossil Butterfly 

 the Palaontina Oolitica of the Stonesfield slate the rela- 

 tionships of which appear to be with some of the living 

 Butterflies of Tropical America. 



Coming to the Mcllusca. the Polyzoans, numerous and 



Fig. Ite.Eryon arctiforrnis, a " Long-tailed Decapod," from the Middle 

 Oolites (Solenhofen Slate.) 



beautiful as they are, must be at once dismissed ; but the 

 Brachiopods deserve a moment's attention. The Jurassic 

 Lamp-shells (fig. 165) do not fill by any means such a pre- 

 dominant place in the marine fauna of the period, as in many 

 Palaeozoic deposits, but they are still individually numerous. 

 The two ancient genera Leptcena (fig. 165, a) and Spirifera (fig. 

 165, b}, dating the one from the Lower and the other from the 

 Upper Silurian, appear here for the last time upon the scene, 

 but they have not hitherto been recognized in deposits later 

 than the Lias. The great majority of the Jurassic Brachiopods, 

 however, belong to the genera Tcrcbratula (fig. 165 c, c, /) 

 and Rhynchonella (fig. 165, d}, both of which are represented 

 by living forms at the present day. The Tcrebratula;, in*par- 

 16 



