BRACHIELLA THYNNI. 205 



spines. First maxillipeds short, stout, and strongly 

 uncinate. The second maxillipeds, which are equal 

 to about two-thirds of the length of the genital seg- 

 ment, slender and free except at the tip, where they 

 are joined to a reddish -brown coloured chitinous plug. 

 Length from the forehead to the end of the posterior 

 appendages of a full-grown specimen about 32 mm. ; 

 length of cephalothorax about 14 mm., of the genital 

 segment about 9 mm., and of the posterior appendages 

 9 mm. 



Male. — Very small, being about a millimetre in 

 length; having a closer resemblance to the male of 

 Lemseopoda than to that of a true Brachiella. 



Habitat. — Parasitic on the gills of the tunny (Orcy- 

 nus thynnus), and other nearly related fishes. Four 

 specimens were obtained by Dr. Bassett-Smith on a 

 tunny captured at Plymouth. 



The female of this species is somewhat similar to B.rostrata 

 in o-eneral appearance, but the cephalothorax is distinctly 

 longer, and the posterior appendages are four in number and 

 much more elongated. 



2. Brachiella rostrata Kroyer. 



(Plate XLV, fig. 8 ; Plate LXII, fig. 3 ; Plate LXIII, 



figs. 2-8.) 



1837. Brachiella rostrata Kroyer. (70) Rekka 1, p. 207, pi. ii, fig. 1. 



1840. Brachiella rostrata M. Edwards. (43) vol. iii, p. 415. 



L863. Brachiella rostrata^'K.rbjer. (71) p. 290, pi. xviii, figs. 8, a-i. 



1877. Brachiella rostrata C. Vogt. (142) p. 426. 



1900. Brachiella rostrata T. Scott. (112) p. 174, pi. viii, figs. 38, 39. 



Female. — Cephalothorax elongated, flexuose or 

 vermiform, and separated from the genital segment 

 by a more or less clearly-defined constriction. Genital 

 segment narrow, subcylindrical, fully three times 

 longer than broad and equal to about one and one- 

 third times the length of the cephalothorax ; posterior 

 end subtruncated and furnished with two subapical 

 appendages. Abdomen obsolete or nearly so. The 

 egg-strings, which are tolerably elongated, arising 

 immediately outside of the subapical appendages. 



