32 CEYLON PEARL OYSTER RETORT. 



crenulate apical margin. This shield is ornamented hy four longitudinal rows of 

 tubercles, two submedian, of about eight tubercles apiece, and two sublateral of four, 

 which lead to an encircling apical ridge, the sloping sides of the shield carrying at 

 the upper part short divergent lines of tubercles, and usually a little tubercle outside 

 each sublateral line. 



The eyes are dark, deeply inserted in the front margin of the peraeon. 

 The first antennae have a broad basal joint, probably representing two joints con- 

 solidated. The following joint is small, scarcely as long as broad. The flagellum in 

 the specimen examined consisted of fourteen joints, the first much the longest, as 

 long as the basal and twice as long as the terminal joint of the peduncle. 



The slender second antenna? are rather longer than the first ; the fourth and fifth 

 joints of the peduncle are equal in length ; the flagellum is fourteen-jointed, rather 

 longer than the peduncle. 



The epistome is somewhat longer than broad ; the upper lip has a feebly trilobed 

 margin. 



The gastric spines on the folds of the stomach at its entrance display a variety of 

 shapes, which, however, may be customary. 



The mandibles have the molar strong and prominent, the palp less slight than 

 usual. In both pairs of maxillae the plates appear to be somewhat broader than is 

 usually the case. 



The maxillipeds have the plate of the second joint broad, strongly setose round the 

 convex distal margin and down the surface at some distance from the inner margin. 

 The latter is armed with an exceptionally long and slender upward-bent coupling 

 spine. The third joint is exceedingly small, the fourth as broad as long, with inner 

 margin narrower than the outer, the fifth about square, like the preceding joint 

 having its inner margin densely fringed with long setae ; the sixth and seventh joints 

 are subequal, apically setose, considerably longer and narrower than the fifth joint. 



The first gnathopods have the hind margin of the second joint setose in its upper 

 part, the third joint nearly as long, with the plumose setse of the front margin very 

 long ; the much shorter fourth joint has long plumose setae on the convex front 

 margin ; the triangular fifth joint is quite small ; the sixth joint is about as long as 

 the fourth, with short plumose setae distally on the front margin and a serrate spine 

 at apex of hind margin ; the finger has minute setules along the concave hind 

 margin. 



The second gnathopod differs from the first chiefly by the cylindrical fifth joint, 

 which is nearly as long as the sixth, the former carrying plumose setae at its front 

 apex, and both being setose along the hind margin. 



The peraeopods are fringed with setae on the front margin of the second, third, and 

 fourth joints, and on the hind margin of all joints from the second or third to the 

 sixth in the first two pairs, and on the corresponding but inverted margins of the 

 other three pairs. The second and third joints are more robust than in the gnathopods. 



