REPORT ON THE CRUSTACEA MACRURA. 327 



calcified process (anceeerite) that is lodged in a depression on the under surface of the first 

 antennae ; the fifth joint of the peduncle coalesces rather than articulates with the fourth, 

 and supports a long and slender flagellum. 



The epistoma is anteriorly produced to a rostriform point, and the cheiloglossa has 

 the labial portion short and divided into two lobular processes that do not cover the 

 mandibles ; the glossal division is reduced in size and unimportant. 



The mandibles are large, powerful, and carry a two-jointed foliaceous synaphipod, 

 the first joint being broad, and the second narrow and pointed ; the right mandible 

 has a more obtuse cutting edge than the left, and they overlap each other instead of 

 impinging at their margins. The metastoma consists of two membranous, subfoliaceous, 

 rounded plates. 



The rest of the oral appendages correspond in form with those of Aristeus rather 

 than with those of Penseus. 



The first pair of gnathopoda is subpediform and carries a long basecphysis, the three 

 terminal joints being permanently flexed upon the preceding one, and the ultimate 

 terminates in two or three apical teeth. 



The second pair of gnathopoda is pediform, carries a long basecphysis, and terminates 

 in a sharp-pointed dactylos. Both gnathopoda support well-formed mastigobranchial 

 plates, which are furnished with large podobranchial plumes. 



The three anterior pairs of pereiopoda are chelate, slender, and increase in length 

 posteriorly ; the two succeeding ones are still longer, more slender, and terminate in simple 

 dactyH. Each pereiopod carries a small basecphysis that becomes gradually less important 

 posteriorly until it becomes rudimentary. The coxa, from the first gnathopod to the 

 penultimate pair of pereiopoda, supports a large and well-formed mastigobranchial plate 

 that increases in length and size, and each, except the posterior, supports a well-developed 

 podobranchial plume that also increases posteriorly. The general arrangement of the 

 branchiae is shown in the following table : — 



Pleurobranchiae, 

 ArtlirobrancHse, 

 Podobranchire, 

 Mastigobranchise, 



The pleopoda are extremely long, and all, except the first pair, are biramose in both 

 sexes. In the male the basal joint of the first pair carries a membranous leaf-like 

 petasma, which in the female is reduced to a rudimentary condition, and the sixth pair 

 is modified to form the outer plates of the rhipidura, which are long, ovate, and 

 lanceolate at the extremity. The outer plate is strengthened by a double marginal 

 rib, terminating in a sub-apical tooth, that coincides with the traces of an obsolete 

 diaeresis. 



