148 Chapman : Palaeozoic Shales. 



,, 3. — Ditto. Profile of valve, x 10. 



4. — An exfoliated dorsal valve, showing impression of median 



septum. Probably Heathcotian. Mount William district, 



xlO. 

 ,, 5. — Ditto. Profile of valve, x 10. 

 ,, 6. — Ditto. Interior of dorsal valve. Probably Heathcotian. 



Mount William district, x 10. 

 ,, 7. — Interior of dorsal valve, showing median septum andl 



muscle scars. Lower Ordovician. Lancefield. x 10. 



