REPORT ON THE CRUSTACEA MACRURA. 853 



13 and 12 mm., while the spinules on the upper margin of the rostrum are thirty, and 

 on the lower fifteen. In Stylodactylus serratus A. Milne-Edwards says that there are 

 forty spines on the upper margin, and more than twenty on the lower, and that the 

 proportion of the rostrum to the carapace is 24 mm. to 20 mm. ; but Stylodactylus 

 serratus is nearly double the size of any of the Oriental specimens. The comparative 

 lengths of the three specimens are as follows : — 



The length of the carapace to that of the entire animal is relatively the same in each, 

 being little less than one-third of the animal, measuring from the orbital margin to the 

 extremity of the telson. The rostrum varies in relative length, and the armature varies 

 still more, especially as exhibited on the upper margin. All the spines articulate with 

 the base on which they stand.' 



In Stylodactylus discissipes the dorsal crest is slightly elevated, and a depression 

 exists on the dorsum corresponding with the cervical fossa, anterior to which the rostral 

 carina ends. The pleon is dorsally rounded, and all the somites are subequal in length, 

 the second being rather the longest. 



The first pair of antennas has the flagella unequal, the inner pair reaching but little 

 beyond the extremity of the rostrum. 



The second pair of antennse has the scaphocerite sharply pointed at the outer distal 

 extremity, and reaches a little beyond the peduncle of the first pair. A long and con- 

 spicuous tooth stands on the outer and distal angle of the second joint of the peduncle 

 at the base of the scaphocerite. The ultimate joint is very stout, and supports a 

 flagellum that is a little longer than the animal, and tolerably strong and not readily 

 detached. 



The oral appendages have not been examined in this the most perfect specimen ; they 

 are described in Stylodactylus orientalis. 



The first pair of gnathopoda are, so far as my experience goes, unique in structure ; 

 they are subpediform ; the basis carries a long, slender, and rather stiff ecphysis, the two 

 succeeding joints are long and robust, and support at the extremity two broad, flat, 

 spatuliform plates that articulate side by side ; they are blunt or rounded at the 

 extremity, and fringed with long hairs. 



The second pair of gnathopoda is pediform, and has six joints ; the meros and carpos 

 are very long, and armed with short spinules and long hairs, the dactylos being either 

 wanting or fused with the propodos. 



