606 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiii. 



four spines, the basal joint slender and one-third longer than the 

 two terminal joints. The second and third joints are the same 

 length; the inner terminal claw is slender and two and a half times as 

 long as the others, equaling the combined length of the second and 

 tliird joints. The fifth legs are entirely lacking. 



The oviducts are rather loosely coiled in the genital segment, 

 and very small compared with the size of the external egg cases. 

 The cement glands are short and wide, somewhat club-shaped, and 

 they reach scarcely beyond the center of the genital segment. Theu- 

 constituent cells are thin, while the duct is enlarged and bent abruptly 

 just as it leaves the cellular portion. The semen receptacle is nar- 

 row, about the same width tliroughout, and curved slightly forwards. 



Total length, 3.2 mm.; length of carapace, 1.65 mm.; length of geni- 

 tal segment, 1 mm.; length of abdomen, 0.55 mm.; width of carapace, 

 1.6 mm.; length of egg strings, 2.15 mm. 



Color a uniform hght gray without pigment except in the eyes. 



(longispinosus, longus, long and spinosus, armed with spines.) 



This species was found on the gills of the Hammer-head shark, 

 Sphyrna zygse-na. It is chiefly remarkable for the length and slender- 

 ness of its spines and maxillae, and also for the form and length of its 

 furca. Specimens were secured from two sharks taken at different 

 times and in different localities. These were all the sharks of this 

 species that were obtained, and of course are not enough to decide 

 whether the parasite is common or not. 



Genus PARAPETALUS Steenstrup and Lutken. 



New diagnosis. — First three thorax segments united with the head 

 and covered by a rounded and sliield-shaped carapace. Frontal 

 plates with lunules as in Caligus. Fourth segment free, much nar- 

 rower than the genital segment, and without dorsal plates or proc- 

 esses. 



Genital segment enlarged nearly to the size of the carapace; its 

 ventral surface produced on either side into a large membranous wing 

 which reaches well beyond the lateral margin of the segment and 

 curls up dorsally at the edge. Each wing is also produced posteriorly 

 into a broad roimded lobe which reaches nearly to the tip of the abdo- 

 men. The genital segment is also produced on its ventral surface 

 posteriorly into two short flattened lobes lying side by side at the 

 median Hue between the bases of the wing lobes and under the origin 

 of the egg tubes. 



Abdomen narrow and elongate; its dorsal surface produced on 

 either side into a wide membranous wing similar to those on the geni- 

 tal segment, but which curls downward at the edges around the egg 

 strings. First and fourth swimming legs uniramose; second and tliird 

 pairs biramose. Fused median eye and furca as in Caligus, Anal 

 laminae medium size with short setse, 



