200 CEYLON PEARL OYSTER RETORT. 



The bony framework is peculiar in its structure, although in some particulars it 

 shows a resemblance to Caligus rapax and other Caliginse. There is in the lower 

 lip a rod (a, fig. 38) along either edge, the two meeting in the centre at the distal 

 end. The bases of these rods articulate on the ventral surface of the carapace 

 together with the mandibles. From these articulations a short rod (b) extends 

 forward and inward on either side along the ventral surface of the carapace. 



From the inner ends of these rods another pair extend upward and inward along 

 the upper lip to the lateral incision opposite the joint (c). From these incisions 

 radiate four pairs of rods, three of which ((/) are in the upper lip, while the fourth 

 pair (e) extend downwards on either side to the rod that rans along the edge of the 

 lower lip. Of the three pairs in the upper lip two extend inward side by side, one 

 above and one below the joint, and meet on the mid-line. The lateral incisions at 

 the joint are deeper than in any of the Caliginse or in Trebius, and the mouth-tube 

 must be very flexible. 



The second maxillse are large and powerful ; although attached opposite the base of 

 the mouth-tube they reach well beyond its tip. The basal portion of each maxilla is 

 enlarged and flattened, and is about one-third of the entire length. The terminal 

 portion is narrowed abruptly and then tapers gradually to a blunt point, being 

 curved first inward toward the mouth-tube and then outward away from it. At the 

 tip each maxilla is divided into two branches, of which the outer one is the longer 

 and the larger. At the end of the basal portion, where it is abruptly narrowed, there 

 is on the ventral surface a large papilla, from whose summit arise three spines, the 

 outer one twice the length of the other two. These represent the rudiments of the 

 exopod of the maxilla (fig. 39). 



The first maxillipeds are of the pattern common to the Caliginse, the terminal joint 

 two-thirds the length of the basal joint and tipped with two claws, the outer of 

 which is three times as long as the inner. 



The second maxillipeds are greatly enlarged, the basal joint stout and swollen and 

 nearly twice the length of the strongly curved terminal claw. On the proximal half 

 of the ventral surface of the basal joint the integument forms a sort of pad with 

 raised edges and a more or less corrugated surface. The distal edge of this pad is 

 raised into a stout knob, down behind which the tip of the terminal claw shuts when 

 closed. 



All four pairs of legs are biramose, the rami of the first pair two-jointed, of the 

 other pairs three-jointed. In the first pair the exopod is a little more than twice the 

 length of the endopod. Its basal joint is three times as long as the terminal one, is 

 heavily fringed with hairs along its posterior margin, and ends in a stout spine. 

 The terminal joint is nearly spherical and is attached at right angles to the basal 

 joint, not at the tip, but some distance back on the posterior border. It is armed, 

 as in the Caliginse, with three terminal spines, three rowing setae, and a smaller 

 seta at the inner distal corner. The endopod joints are about the same size, the 



