REPORT ON THE CRUSTACEA MACRURA. 487 



The species of this genus are generally more slender than in Crangon, a circumstance 

 partially due to the increased length of the sixth somite of the pleon. The rostrum is 

 longer and generally extends beyond the extremity of the ophthalmopoda, it is somewhat 

 compressed laterally, and never dorsally flattened as in Crangon, and the body of the 

 animal is slightly compressed laterally. 



The ophthalmopoda are short and the ophthalmus orbicular. 



The first pair of antennae has the flagella longer than the peduncle, and the stylo - 

 cerite is more styliform than in Crangon. 



The second pair of antennae and the oral appendages offer no very decided character 

 for generic distinction. 



The first pair of gnathopoda carries a small podobranchial plume attached to the 

 mastigobranchial lash. The second pair is longer and more slender, but, like that of 

 Crangon, is only five-jointed, and supports a small basecphysis and the rudiment of a 

 mastigobranchial organ. 



The first pair of pereiopoda closely resembles that of Crangon, being subchelate and 

 robust ; the second also resembles that of Crangon in being chelate, yet it differs in 

 being short, slender and feeble ; it only reaches to the mouth, to which it most probably 

 carries food. The third pair is long, slender and styliform, the length being chiefly due 

 to the terminal three joints, the carpos, propodos and dactylos. The posterior two pairs 

 are long and robust. 



The pleon is ventrally smooth, and the pleopoda are foliaceous, and furnished with 

 two stylamblydes both in the male and female, attached to the inner branch of every 

 pair except the first. 



The posterior pair, which forms the outer plates of the rhipidura, is long, narrow, and 

 furnished with a diaeresis. The telson is long and narrow, but shorter than the lateral 

 plates. 



Geographical Distribution. — The range of this genus is probably cosmopolitan, and 

 in tolerably deep water. Specimens of four species have been taken in the British seas, 

 and in the Challenger collection there are species from the Celebes Sea, mid-south 

 Atlantic, New Zealand, and the Philippine Islands. 



Pontophilus gracilis, n. sp. (PI. LXXXVII.). 



Carapace armed with three teeth on the median ridge, two close together on the 

 o-astric region and one above the cardiac, one on each side near the middle of the lateral 

 carina, and a hepatic tooth just anterior to the branchial region. 



Pleon smooth, third somite longer than the fourth. 



