80 CEYLON PEARL OYSTER REPORT. 



exceptionally well marked and deep. The antennular peduncle is short, and is only- 

 half the length of the rostrum. Its proximal joint is the largest, being equal to the 

 sum of the other two. There are two branches to the flagellum. The inner branch 

 reaches slightly beyond the rostrum, and the outer branch, which is slightly shorter, 

 is much thicker and plumose, and shows signs of bifurcation at the tip. The 

 antennular scale is almost as long as the peduncle. The antennal peduncle is as long 

 as that of the antennule. The flagella are broken in both specimens. The scale is 

 stout and reaches to the end of the rostrum. The mouth parts are similar in all 

 important respects to those of Nauticai'is manonis. 



The 3rd maxillipeds reach past the end of the rostrum and have the distal joint 

 tipped by about five well-marked spines. The proportionate lengths of the joints are 

 similar to those of N. marionis. There are only four joints, and the second bears a 

 large spine at its distal end. The 3rd joint is richly setose on its anterior face. The 

 legs are robust, excepting the 2nd pair. The 1st pair are chelate and reach a little 

 past the end of the antennal peduncle. The 2nd pair are long and slender and have 

 a multi-articulate wrist. They reach to the extremity of the rostrum, the 3rd, 4th, 

 and 5th pairs are similar to one another in form, decreasing slightly in length from 

 before backwards. The 5th leg reaches to the base of the antennal scale. The 

 carpos of each of the last three pairs bears a blunt process at the anterior distal 

 border. The dactylos ends in two larger spines, and bears several smaller spines on 

 its posterior border. The abdomen is robust and bent at right angles at the 

 3rd segment. There are two spines on the ventral side of each of the first four 

 abdominal segments, and on the ventral side of the 5th and 6th segments there is a 

 long median spine pointing backwards. The 6th abdominal segment has a well- 

 marked movable spine at each of its posterior lateral borders, and also bears two 

 well-marked spinous processes on its posterior border overhanging the telson. The 

 uropods are slightly longer than the telson. The 2nd abdominal segment has a small 

 transverse groove in the mid-dorsal line. 



The telson tapers somewhat posteriorly and has a slightly grooved dorsal surface 

 carrying two pairs of spines. The posterior border bears two pairs of spines and 

 numerous long hairs. 



Dimensions (measured along mid-dorsal line) : 



From tip of rostrum to end of telson . . . . 50 millims. 



Rostrum and carapace 20 ,, 



Carapace 11 ,, 



1st abdominal segment 2 ,, 



^nrl 4 



3rd ,, ,, 8 



4th 51 



6th ,, ,, 3a ,, 



Telson 5|- ,, 



