REPORT ON THE CRUSTACEA MACRURA. 333 



The external tissue is soft and membranous. 



The rostrum is short, and tapers rather suddenly to a sharp point. The crest is narrow, 

 armed with two small teeth, and the carina can be traced to very nearly the posterior 

 margin of the carapace. The dorsal surface of the pleon is smooth until the third somite, 

 where a small carina commences, which culminates in a small but distinct tooth in the 

 median line of the posterior margin of the third, fourth, and fifth somites, and increases 

 to a distinct carina on the sixth somite, terminating abruptly on the posterior margin. 



The telson is dorsally flattened, laterally compressed, tapering, and armed on each side 

 with three small spinules ; the last two are subapical, and between them are two others. 



This species is exceedingly Uke Benthesicymus alius, but may at once be distinguished 

 from it by the soft membranous condition of the external tissues, the presence of the 

 small tooth on the posterior margin of the three somites preceding the last, and the 

 absence of the transverse elevation of the posterior margin of the sixth somite. 



The ophthalmopod is obliquely flattened, soft, and flexible, and is furnished near 

 the middle of the inner margin with a very decided blunt tubercle, with a single lens. 



The ophthalmus is orbicular, equal in breadth to the greatest diameter of the flattened 

 stalk, and of a yellowish- white colour; a little dark pigment lies at its base near the 

 centre. The ophthalmopod reaches as far as the extremity of the rostrum and equals 

 the stylocerite in length. 



The first joint of the first pair of antennae extends a little beyond the extremity of 

 the eye, and is armed on the outer side with a stylocerite that is large and flattened 

 on the outer side, and has no tooth on the distal angle, but is reduced to a mere point 

 at the extremity. The next two joints are short and terminate in two long, rather rigid, 

 multiarticulate flagella. 



The second pair carries a long and broad scaphocerite that terminates in an ovate 

 extremity, and is strengthened by a median rib and an external ridge that ends in a 

 small tooth considerably short of the extremity ; on the inner side of the coxal joint is 

 a small phymacerite, and on the upper side of the third joint of the peduncle a small, 

 rigid, fixed hook (ancecerite); it terminates in a long and slender flagellum. 



The other appendages may be compared with those of Benthesicymus altus. 



The pereiopoda, especially the chelate pairs, are long and more slender. The ventral 

 surface of the pereion, in the female, is thickly matted with hairs ; the oviducts are 

 large and come into contact with those on the opposite side ; between the fourth pair is 

 an ovate thelycum directed anteriorly, behind which the surface is small and smooth, 

 and there is no tooth or tubercular process between the first pair of pleopoda. 



The first pair of pleopoda in the female is similar to that in Benthesicymus altus. 

 In the male the petasma is moderately large, pear-shaped, and carries a marginal process 

 on the outer side. The second pair has two rami, one long, the other very short and 

 slender, and at its base a small scale-like plate. All the others are sirndar in both sexes, 



