Bull. U. S. B. F., 1924. i Doc. 968.) 



'i 1 '- 12 Segments of the branchial iieves of tin oinmon Ashe; thai feed "ii plankton, a. Menhaden, I ecoo 



tyrannus; b, herring, Clupea harengus; r, mackerel, Scombei scombrur; d, mackerel, side view ol Bill raker, with 

 gill spines, x 25 



