280 THE VOYAGE OF H.M.S. CHALLENGER. 



There is only one specimen of this species and that is imperfect, but in its general 

 aspect it appears to belong to this genus, and carries a post-antennal as well as a hepatic 

 tooth, but the broken condition of the first pair of antennas precludes me from determining 

 the exact relationship. 



The form of the petasma is very distinct from that of any other species known to me, 

 either of this genus or Penseus, and one that will readily be recognised from its series of 

 curved, comb-like teeth. 



The smaller rami of the branchiae (br") are short, laterally compressed, dichotomous 

 and obliquely attached to the larger branch. 



The mastigob ranch ial plates (mb) are broad, forked, and supported on a cylindrical 

 stalk that has a lateral lobular prominence near the coxal articulation. The stalk is sup- 

 ported by a series of globular deposits of lime crystals. 



The ultimate structure of the branchial plumes approximates to that in Philonicus 

 miilleri, and consists of a series of compressed branches that terminate in flattened lobes, 

 and of others broader and more foliaceous that terminate in papilliform processes. 



The flagella of both pairs of antennae, the second pair of gnathopoda, and all the 

 pereiopoda are broken off close to their origin. The first pair of pleopoda, with its 

 comb-like, fringed petasma, as well as the four succeeding pairs and the rhipidura, are 

 preserved. The rostrum is broken but not detached. 



Artemesia, n. gen. 



Rostrum long, slender, and pointed, armed with a few teeth on the dorsal crest ; body 

 compressed, with a tendency to form a carina, more especially on the dorsal surfae of 

 the pleon. 



Ophthalmopoda biarticulate and ophthalmi ovate. 



First pair of antennae having a stylocerite and prosartema attached to the first joint 

 of the peduncle, and two subequal flagella that are as long as the carapace. 



Second pair having a scaphocerite and a long and slender flagellum. 



Mandibles furnished with a two-jointed, broad, foliaceous synaphipod. 



First pair of gnathopoda short, six-jointed and subpediform, the two distal joints 

 being reflexed against the inner margin of the ischium and meros. The basis carries no 

 ecphysis and the coxa supports a mastigobranchia with a podobranchial plume. 



Second pair of gnathopoda pediform, seven-jointed and straight. The basis carries 

 a long and slender ecphysis, but there is no mastigobranchia nor podobranchia, but two 

 arthrobranchial plumes are attached to the membranous articulation. 



First three pairs of pereiopoda chelate, slender, and each carries a small basecphysis 

 and a pedunculated and forked mastigobranchia, but no podobranchia ; the last two 

 pairs are slender and simple, the posterior being longer and more slender than the pre- 



