EEPORT ON THE CRUSTACEA MACRURA. 511 



The first pair of antennas (PI. XCII. b $ b ?) has the peduncle extending to the 

 extremity of the rostrum in the male, and a little beyond it in the female. The first joint 

 reaches beyond the anterior margin of the eye, and is excavate in its entire length to 

 receive that organ ; near its base it is lobed on the inner side, where the acoustic organ is 

 situated, the opening of which is on the lower external surface, beneath a squamiform 

 process or plate (b" $). The second joint is about half the length of the first and sub- 

 cyliudrical. The third is shorter than the second and terminates oblicpiely, the inner 

 angle, which is the more advanced, supports the inner, shorter, and less important 

 flagellum, the outer angle, which is broad and oblique, supports the primary or more 

 important flagellum, w T hich in the male is thicker than in the female. It is formed by 

 a large number of short articuli that are broad at the base and for about half the length 

 of the appendage, and then rapidly diminish as the flagellum gradually narrows to 

 a slender lash. The upper side of the thicker portion is flattened, while the lower is 

 rounded and supplied with numerous fine membranous cilia which are more numerous 

 in the male than in the female. 



The second pair of antennas (c $) has a peduncle that does not reach beyond the 

 extremity of the second joint of the peduncle of the upper. The coxa or first joint is 

 very short and supports a prominent phymacerite on the inner side, the second is broad 

 and at its outer angle supports a large oval scaphocerite, which thins out on each side 

 from the central line, and is fringed all round with long cilia. The outer margin is rigid, 

 and the tooth which is so universally prominent in the Macrura is reduced to a rudi- 

 mentary condition, so as to be invisible to the unassisted eye, but a rigid margin is 

 traceable for some way from the base. The third and fourth joints are oblique to each 

 other and both articulate with the second at the antero-internal margin ; the fifth joint 

 is narrow, cylindrical, and as long as the four preceding. 



The mandibles (d) are small and consist of a molar process only, and are enclosed 

 deeply within the oral cavity so that they are entirely covered over by the cheilogiossa 

 and metastoma. 



The first pair of siagnopoda (e) is small, lying closely pressed against the posterior 

 surface of the metastoma ; it consists of three branches, the central of which is fringed 

 with stiff hairs. 



The second pair of siagnopoda (f) consists of a rudimentary one-jointed appendage, 

 supplemented by a broad, thick, fleshy plate, which bears a thick fringe of hairs, 

 centrifugally planted on its margin. 



The third pair of siagnopoda (g) consists of two foliaceous plates, the outer of which 

 supports a lash-like appendage, and a thick, fleshy, smooth margined plate that tapers and 

 projects anteriorly as well as posteriorly. 



The first pair of gnathopoda (h) is short, subpediform, and consists of seven joints. 

 The coxa and basis are subequally short and wide ; from the latter a long, slender, lash- 



