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



lying contiguous to the inner margin of the smaller and inner branch. All the other 

 pairs are of merely generic value. 



The posterior somite of the pleon is long, being nearly twice the length of the 

 preceding one. 



The telson is not so long as the inner plate of the rhipidura ; it is sharp-pointed, 

 dorsally grooved, and armed at the margins on each side near the distal extremity with 

 three long spines and with one posterior, rigid, slender spine-like tooth. 



In the female the peduncle of the first pair of antennae does not reach quite as far as the 

 extremity of the rostrum, and the scaphocerite attached to the second pair is also shorter. 



The sexual tubercle attached to the coxa of the third pair of pereiopoda (fig. 2") is 

 longer than usual, projects obliquely backwards, and does not approach so near to 

 its fellow as is generally the case in other species. The thelycum consists of two longi- 

 tudinal plates united together in a straight line in the centre, and lobed on the outer 

 sides, being held in position by clamp-like lateral processes, but which can best be 

 understood by reference to the Plate (fig. 2"). In all other respects, except in the absence 

 of the secondary sexual organs, the female resembles the male. 



Habitat.— Station 192, September 26, 1874; lat. 5° 49' 15" S., long. 132° 14' 15" E.; 

 off the Ki Islands, south of Papua; depth, 140 fathoms; bottom, blue mud. Two male 

 specimens ; trawled. 



Station 201, October 26, 1874; lat. 7° 3'N., long. 121° 48' E.; off the Celebes Islands; 

 depth, 82 fathoms ; bottom, stones and gravel. Twenty-seven specimens ; ten females, 

 seventeen males ; trawled. 



Station 219, March 10, 1875; lat. 1° 54' S., long. 146° 39' 40" E. ; off the 

 Admiralty Islands; depth, 150 fathoms; bottom, coral mud. Numerous specimens; 

 associated with Panulirus angulatus. Eight males and two females ; trawled. 



Observations. — The animal is slender, and has the pleon long, the sixth somite being 

 twice the length of the preceding one. In the male specimens the rostrum is straight, 

 being in the same horizontal plane as the dorsal surface of the carapace, and not gradually 

 elevated from the base as in Penaeus velutinus. 



In most of the adult female specimens the extremity of the rostrum is slightly 

 elevated. The eyes are very similar to those of Penaeus velutinus. The first pair of 

 antennas has the flagella slightly longer, and the stylocerite on the outer margin is united 

 to the first joint for half its length and then curved upwards, and is scarcely as long as 

 in Penaeus velutinus, and the prosartema is more pointed. The synaphipod attached 

 to the mandible is covered with a thick fur on the lower and external surfaces. 

 In most respects the other parts resemble those described in Penaeus velutinus, except- 

 ing that the posterior two pairs of pereiopoda, which in Penaeus philippinensis 

 have the dactylos shorter and less flattened than in Penaeus velutinus, have a furrow 



