REPORT ON THE CRUSTACEA MACRURA. 133 



The posterior margin is deeply excavated in the centre, from which the margin, 

 fringed with a row of minute hairs, recedes posteriorly and outwardly on each side to a 

 strong tubercle, the peltecleis, which overrides and articulates in a hollow or socket 

 formed in the coxal plate of the first somite of the pleon. From this tubercle the 

 posterior margin passes downwards and outwards, and becomes continuous with the 

 lateral margin. From this point also an obscure line, slightly baccated in appearance, 

 passes in a flexuous direction forwards on the dorsal surface of the carapace, correspond- 

 ing with the internal wall of the branchial chamber. 



The first somite of the pleon has the anterior division long and the posterior short ; 

 the former is smooth, and passes beneath the carapace, when the animal is extended ; 

 the latter is granulated, and is armed with a strong anteriorly-directed tooth in the 

 median line, and extends laterally until it reaches the coxal plate, which is produced 

 obliquely forwards, and overlaps the posterior margin of the carapace, external to the 

 tuberculated process or peltecleis, and thus secures or bolts the carapace in position. 

 The second somite is not longer than the first, but has the first or anterior division 

 shorter and covered almost entirely by the previous somite when the animal is 

 extended ; the posterior division is longer, granulated, and divided transversely by a 

 groove or furrow that runs obliquely from near the anterior margin at the median lino 

 to the postero-lateral margin, where it joins with the coxal plate. A large sharp 

 anteriorly-directed tooth longitudinally traverses the posterior division in the median 

 line ; the coxal plate is extremely large, being produced forwards to an obtuse point 

 beyond the margin of the carapace downwards and inwards, and rounded inferiorly 

 and posteriorly in a continuous line ; the upper portion of the surface is granulated, the 

 lower smooth, and the margin fringed with long hairs. The third, fourth, and fifth 

 somites resemble the second, excepting that they gradually narrow posteriorly, and the 

 tooth on the dorsal median line becomes less important in the fourth, and only appears 

 as a ridge or crest on the fifth somite, and also in the form of the coxal plates, which 

 are not produced anteriorly, but have the anterior margin hollowed, uniting with the 

 posterior margin so as to form an obtuse angle with it. The sixth somite is narrower 

 and slightly longer than the preceding ; the coxal plate is more pointed and posteriorly 

 excavate, to admit of the articulation of the posterior pair of pleopoda ; the dorsal 

 median line instead of being armed with a vertical tooth is furnished with a double 

 row of small bead-like tubercles. The telson is long, pointed, horizontally ribbed, and 

 fringed with long hairs. There appears to be no feature in the dorsal structure that 

 distinguishes the male from the female, which is slightly the larger in our specimens. 



The ophthalmopoda (fig. lc, a) are small, obscure, anteriorly armed with a small tooth, 

 and lodged in an orbit excavated in the anterior margin of the carapace, compressed on 

 the under side by the membranous articulation of the second pair of antennas, and point 

 outwards, covered by the projection of the latero-anterior angle of the carapace, and 



