198 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



TISBE WILSONI Seiwell 



Figures 131c, 132 



TishG wilsoni Seiwell, Proc. U. S. Nat. Mus. vol. 73, art. 18, p. 3, pi. 2, 1928. 



Occurrence. — Both sexes were obtained from the common sea pork, 

 A'ma7'ouciu?7i, collected near Woods Hole in the summer of 1925. 



Color. — Female creamy white and fairly transparent, ovaries and 

 oviduct dark brown; male grayish white with a dark patch in the 

 epimeral plate on either side of the first four thoracic segments. 



Feinale. — Body slender, metasome oval, twice as long as wide, 

 urosome less than half the length of the metasome; genital segment 

 divided at the center; caudal rami longer than anal segment, apical 

 setae half the body length. First antennae 8-segmented and strongly 

 tapered, especially distally; exopod of second antennae 4-segmented, 



attached to side of basal segment of en- 

 dopod. Endopod of first legs twice as 

 long as exopod, second segment longer 

 than first, end segment spherical, its two 

 apical claws without plumes. Basal seg- 

 ment of fifth leg not much widened, its 

 inner expansion with three setae; apical 

 segment laminate, its width two-fifths of 

 its length, with three end setae and two on 

 the outer margin. Total length, 0.94 mm. 

 Male. — Body much more slender and 

 elongated than that of the female; uro- 

 some 5-segmented, the genital segment 

 divided in front of its center, and slightly 

 tapered backward, caudal rami as wide as long. First antennae 

 geniculate, the terminal portion made up of two segments; second 

 antennae, mouth parts, and first four pairs of legs as in the female. 

 Fifth legs 2-segmented, basal segment without either inner expansion 

 or outer process, terminal segment nearly as wide as long with two 

 apical and one lateral setae. Total length, 0.7 mm. 



Remarks. — This species is chiefly distinguished by the fact that 

 it lives commensally in an ascidian. It conforms closely to the 

 genus type except in the fifth legs of the male, which are consider- 

 ably degenerated. 



CHAPPAQUIDDICKA, new genus 



Head fused with the first segment ; metasome considerably de- 

 pressed, the first 4 thoracic segments with broad epimeral plates, 

 the fifth segment abruptly narrowed to half the width of the fourth 

 and without lateral plates; urosome half as long and less than half 



Figure 132. — Tis\>e wilsoni: a, 

 Male, fifth leg ; h, female, 

 fifth leg (variant) 



