FRESH-WATER NEREIDS FROM THE PACIFIC COAST AND HAWAII. 223 



PLATE XVII. 



Figs. 17-23, Ltcastis hawaiiensis sp. nov. 



Fig. 17. Anterior extremity of a medium-sized specimen. X16.5. 



Fig. 18. Posterior extremity, young specimen. X23. 



Fig. 19. Anterior extremity with everted proboscis, largest specimen. X 17. 



Fig. 20. Posterior aspect of eighteenth foot. X40. 



Fig. 21. Longitudinal section of distal extremity of foot, showing retractile tip extruded. X150. 



Fig. 22. Section of epidermis and circular musculature, with blood-vessels in solid black, penetrating the epidermis. 



X275. 

 Fig. 23. Horizontal section of a dorsal cirrus, showing vascular loops. Their cut ends are almost in contact with 



thecuticula. X275. £ 



Figs. 24-27, Lycastoides alticola gen. nov.", sp. nov. 



Fig. 24. Anterior extremity. The specimen is mounted in balsam, hence the jaws, pharynx, etc., are visible. X40. 



Fig. 25. Posterior aspect of a foot from the middle region (tip partially retracted). X75. 



Fig. 26. Optical section of distal extremity of foot with fully retracted tip, in cedar oil. Basal portions only of 

 v the setae are shown. X75. 



Fig. 27. Foot with fully protruded tip. X75. 



Fig. 28. Transverse section of N. agassizi Ehlers, for comparison with Fig. 29. X23. 



Fig. 29. Transverse section of Nereis limnicola, showing the depressed form and slight development of the muscu- 

 lature. The blood-vessels are represented in solid black. Diagrammatic as to histological detail. 

 X23. 



