Note on a Crayfish at the Melbourne University. 161 



afibrds additional proof of the generally accepted view as to the 

 derivation of the ambulatory appendages from the primitive 

 biramose type. Their occurrence in an isolated specimen out of 

 the many hundreds which have been examined by various 

 workers is, doubtless, to be explained as an instance of reversion 

 to an ancestral condition. An analogous case is afforded by the 

 "antenniform ophthalmite" of Palinurus penicillatus described by 

 Professor Milne-Edwards, and subsequently figured by Professor 

 Howes in the Proceedings of the Zoological Society of London 

 (17th May, 1887). 



My thanks are due to Mr. A. W. Morton for calling my 

 attention to the specimen described above, which is preserved in 

 the Museum of the Biological School. 



