REPORT ON THE CRUSTACEA MACRURA. 281 



ceding, and neither of these carries a basecphysis or mastigobranchia, and the posterior 

 is without any branchial plume at all. 



The branchiae somewhat resemble in structure those of Penseus, but the dendritic 

 branches appear to be more simple. 



The following table shows their general arrangement : — 



Pleurobranchise, 

 Arthrobranchiae, 

 Podobrancliise, 

 Mastigobranchia?, 



The fourth pair of pereiopoda has two well-developed plumes, but one is pleurobranchial, 

 interstitial between the fifth and sixth somites, and in one or more instance I have 

 observed a rudimentary ecphysis attached to the basisal joint. 



This genus bears some external resemblance to Aristeus, but differs in having two 

 long flagella to the first pair of antennae, in the form of the synaphipod and mastigo- 

 branchia?, in the number of the branchiae, in having no podobranchia except the one 

 attached to the first pair of gnathopoda, and in the ultimate structure of the branchiae. 



In some of these points it corresponds with Philonicus. 



Geographical Distribution. — As yet we only know one species of this genus, which 

 was taken off the east coast of South America. 



Artemesia longinaris, n. sp. (PI. XL.). 



Carapace dorsally smooth and produced anteriorly to a horizontal rostrum that is 

 half the length of the animal, measured from the orbit to the posterior extremity of the 

 telson. Eostrum crested over the base and armed there with nine or ten teeth, from 

 which to the apex it is smooth both above and below. The pleon is smooth to the fourth 

 somite, which is dorsally angulate. The fifth and sixth somites are slightly carinated, 

 the carina on each being produced posteriorly to a small tooth. 



The ophthalmopod reaches nearly to the extremity of the serrate crest, and the 

 ophthalmus is ovate. 



The first antennae carries a prosartema that does not reach to the extremity of the 

 ophthalmopod, and a stylocerite that is short and almost rudimentary ; the peduncle 

 reaches to about half the length of the antennae, supporting two flagella that are twice 

 the length of the rostrum. 



The second pair of antennae carries a scaphocerite that reaches as far as the distal 

 extremity of the peduncle of the first pair, and a flagellum that is once and a half as long 

 as the animal. 



The pereiopoda are slender and not very long. 



(ZOOL. CHALL. EXP. — PART LIL — 1886.) Fff 36 



