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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 52 



'drink its mother's milk' like a mammal, even though the milk-like 

 secretion does not go in at the mouth, but by channels homologous 

 with the ear-drum of air-breathing vertebrates." 









Fig. 55. — Ptcrophitcca viicnira. After Alcock. 



