Micrographs of cystacanths and adults of Profilicollis altmani from Emerita analoga and from Larus belcheri, respectively on the Peruvian coastline, Lima. 17–20. Lateral views of hooks and roots of one longitudinal row on the proboscis of a cystacanth. 17. Apical and 2 subapical hooks and roots. 18. Hook nos. 4, 5, and 6 with their roots. Note the shorter and thickest hook no. 5 (at middle). 19. Hook nos. 7–10; note the increasing size of hooks posteriorly. 20. Hook nos. 11–15. Note the increasing size of hooks posteriorly being longest and more crowded basally. 21. Fan shaped anterior end of proboscis receptacle inserted at the posterior end of the proboscis. Note the heavy muscular fibers of the neck (arrows). 22. Double-walled proboscis receptacle (arrow) within the neck of an adult specimen directly posterior to attachment to proboscis.