406 



BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



CALIGUS MUTABILIS Wilson 

 FiGtTBB 253 

 Valigus mutabilis Wilson, Proc. U. S. Nat. Mus., vol. 28, p. 573, pi. 8, 1905. 



OccwTence. — Both sexes found in the mouth of the blackfish, 

 striped bass, pollack, and bonito at Woods Hole. 

 Distribution. — Not found outside the present area. 

 Color. — Body a light horn yellow, delicately penciled with small 

 spots and lines of pink and red, which are most prominent along the 

 dorsal midline and on the posterior lobes of the carapace ; eye bright 

 ruby red. 



Female. — Carapace less than half the entire length; lunules large, 

 circular, and projecting slightly; fourth segment one-fourth the 

 width of the carapace, strongly narrowed in front of the fourth legs ; 



genital segment flask-shaped, con- 

 tracted into a short waist anteriorly, 

 slightly concave posteriorly, with- 

 out lobes or leg rudiments. Ab- 

 domen 2-segmented, segments about 

 equal; caudal rami small, widely 

 separated; furca the shape of a 

 rounded Y; fourth leg 3-segmented, 

 with five spines and no seta. Total 

 length, 5-5.75 mm. 



Male. — Carapace more than half 

 the entire length; fourth segment 

 wider than the genital segment and 

 contracted but little in front of the 

 fourth legs; genital segment spin- 

 dle-shaped, one-half longer than 

 wide, without leg rudiments. Abdomen 2-segmented, the basal seg- 

 ment more than half as long as the end segment ; caudal rami large 

 and laminate, as wide as long. Total length, 3-3.5 mm. 



Remarks. — This species can be distinguished from the others here 

 included by the fact that the abdomen is as long as the genital seg- 

 ment and 2-segmented. The shape and relative size of the genital 

 segment in the female, however, vary greatly with the stage of devel- 

 opment of the individual, whence the specific name. 



CALIGUS PELAMYDIS Kr0yer 



FiGUEB 254 



CaUffus pelamydis Kr0yer, Naturh. Tidsskrift, ser. 3, vol. 2, p. 50, pi. 4. 

 1863.— Wilson, Proc. U. S. Nat. Mus., vol. 28, p. 594, pi. 13, 1905. 



Occurrence. — Found on the gills of the oceanic bonito {Gymno- 

 sarda pelamis) at Woods Hole. 



Figure 253. — Caligus mutabilis: a. Fe- 

 male, dorsal ; i, female, fourth leg 



