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



receive the smaller one as in Solenocera, Lucas. Both flagella exceed in length that 

 of the carapace. 



The second pair of antennae is furnished with a large scaphocerite that generally 

 equals the length of the peduncle of the first pair, and terminates in a slender flagellum 

 of great length. 



The mandibles have a two-jointed, long, broad and foliaceous synaphipod ; of which 

 the second joint is narrow, but not longer than the first, and reaches as far forwards as 

 the distal extremity of the peduncle of the second antenna. 



The oral appendages do not differ much from those of Penseus. 



The first pair of gnathopoda carries a basecphysis that reaches to the distal extremity 

 of the meros, and the coxal joint supports a mastigobranchia that is pedunculated and 

 supports a branchial plume at its base. 



The second pair of gnathopoda is long, pediform, and carries a small basecphysis 

 and a mastigobranchia that is slightly forked at its distal extremity, but without a 

 branchial plume. 



The anterior three pairs of pereiopoda are chelate but neither stout nor very long. 

 The posterior two pairs are long and slender, the ultimate being about two-thirds the 

 length of the entire animal. Each pah- carries a small basecphysis diminishing to a rudi- 

 mentary condition posteriorly. The mastigobranchia? are all long and pedunculated, but 

 carry no branchial plume. 



The entire series of the branchial apparatus may be tabulated as follows : — 



Pleurobranchife, . . ....1 1 1 1 1 1 



Arthrobranchiae, . . .122222... 



Podobranchiae, 



Mastigobranchise, 



The male carries a large petasma attached to the basal joint of the first pair of 

 pleopoda. The rhipidura is long and narrow, the outer branch showing traces of an 

 obsolete diaeresis. 



The telson is narrow and slender. 



This genus resembles Penseus in the character of the ophthalmopoda, which are 

 Inarticulate and supported on a free and exposed somite, but Penseus may readily be 

 identified from it — 



1. By the postantennal teeth on the frontal walls of the carapace. 



2. By the length of the antennae, the flagellum of the second pair being three times 

 the length of the animal, or more. 



3. By there being two arthrobranchial plumes attached to the penultimate pair of 

 pereiopoda, and by the presence of a podobranchial plume attached to the mastigo- 

 branchial plate of the first pair of gnathopoda. The presence of which is an essential 



