REPORT ON THE CRUSTACEA MACRURA. 777 



The second pair of siagnopoda (fig. 3/*) is four-branched, and carries a mastigobranchial 

 plate that extends backwards as a long and narrow process, fringed on the inner side with 

 long hairs that reach to the posterior extremity of the branchial chamber. The other 

 branches are short, foliaceous, and fringed with hairs. 



The third pair of siagnopoda (fig. 3g) is three-branched, and carries a bilobed mastigo- 

 branchia ; the inner branch is broad, foliaceous, and fringed with fine hairs, the middle 

 branch is triarticulate and fringed with fine hairs, the third or outer is broad and foliaceous 

 at the base and suddenly narrows distally to a long and tapering flagellum fringed with 

 hairs. 



The first pair of gnathopoda (fig. 3h) is subpediform and seven-jointed ; the propodos 

 is broad and reflexed ; the basis carries a long and slender ecphysis and the coxa supports 

 a short membranous mastigobranchia without a branchia, but a short arthrobranchial 

 plume is attached to the membranous articulation. 



The second pah- of gnathopoda (fig. 3/) is long, slender, and pediform. The coxa carries 

 a short and rigid mastigobranchia, armed with a small hook but without a podobranchial 

 plume, but an arthrobranchia is attached to the membranous articulation ; the basis carries 

 a well-developed but not long ecphysis, and the distal joints are fringed with minutely 

 ciliated hairs. 



In the only specimen all the pereiopoda were broken off previously to my finding it 

 among a number of specimens of Campylonotus semistriatus, excepting one of the third 

 and one of the fifth pairs on the right side ; these are moderately long, tolerably robust, 

 and terminate in a short and simple unguiculate dactylos. 



The pleopoda are brramose, the first pair has the rami unecjual, the inner being the 

 shorter. The others are subequal and the inner branch carries a stylamblys. 



The rhipidura is well developed, the lateral plates being longer than the telson, and 

 the outer has a diaeresis. 



Observations. — A careful comparison of this species with others of its own genus, and 

 of Chorismus and Merhippolyte, is instructive as throwing light upon the mysteries of 

 specific variation. 



If we compare the external form of Campylonotus vagans with that of Chorismus 

 tuber culatus, we perceive that it corresponds more nearly to it than to its generic ally 

 Campylonotus semistriatus. The only external distinction between them that may be 

 considered to be specific is that Campylonotus vagans has the sixth somite of the pleon 

 comparatively longer, and there is a prominence on the anterior margin of the first and 

 on the posterior margin of the fourth somites of the pleon, but an examination of the 

 branchial apparatus shows that, while Chorismvs has only seven branchial plumes on 

 each side, Campylonotus has twelve, and in this respect agrees with Merhippolyte. 



Had the solitary specimen of Campylonotus vagans been a perfect one there would 

 have been little difficulty in determining its generic position, but the first two pairs 



(ZOOIi. CHALL. ESP. PART LIL — 1887.) Fff 98 



