REPOET ON THE CRUSTACEA MACRURA. 7 Go 



first pair is shorter than the second and carries a longer basecphysis. The three 

 terminal pairs of pereiopoda are subcylindrical and terminate in a styliform dactylos ; 

 they all carry a basecphysis, which gradually decreases posteriorly, and each a mastigo- 

 branchial appendage, except the posterior pair. The mastigobranchise are small, but 

 cannot be considered as rudimentary, since they carry a membranous plate that passes 

 to a considerable distance between the branchial plumes, except the penultimate pah 1 , 

 which has only the rudimentary stalk. The branchiae are long, the posterior pleuro- 

 branchial and arthrobranchial plumes being particularly so ; the foliaceous plates are long 

 and narrow. 



The first two somites of the pleon are dorsally smooth and laterally broad, deep, and 

 rounded anteriorly ; the third, fourth, and fifth are dorsally produced posteriorly into a 

 styliform tooth that is subequal in length to the next succeeding somite, against the 

 surface of which they lie, forming a sharp carina when the animal is extended, but 

 when the rhipidura is compressed against the ventral surface of the pereion the dorsal 

 teeth are elevated into formidable defensive weapons. The lateral coxal plates at- 

 tached to these three somites are lunate, being excavated on the anterior margin 

 and convex on the posterior, so that they are produced to a point at the infero-anterior 

 margin. 



The pleopoda are all biramose and subfoliaceous, the inner margin of the anterior 

 plate being furnished with a broad and flat stylamblys in the female, to which sex all our 

 specimens belong. The posterior pair, which helps to form the rhipidura, is shorter than 

 the telson ; the inner plate is narrow and pointed, the outer is broad and carries a diaeresis 

 armed with a small tooth on the outer angle. 



The telson is long, sharp, and style-like, dorsally flat and laterally compressed, with 

 one or two obsolete spines. 



The ova are large, somewhat ovate, and about one-eighth of an inch in length ; they 

 are not numerous, being about a dozen in number, and the embryo appears to quit the 

 ovum in the Zoea condition. 



Oplophorus longirostris, n. sp. (PL CXXVII. fig. 2). 



Like Oplophorus typus, but it differs in having the rostrum nearly as long again as 

 the carapace, having eleven teeth on the upper surface and eight on the lower, the tooth 

 at the postero-inferior angle of the carapace pointed outwards and forwards, the scapho- 

 cerite much shorter than the rostrum, and the antero-inferior margin of the coxal plate 

 of the first somite of the pleon slightly excavate and the inferior margin produced to a 

 point or tooth. 



The dorsal teeth on the third, fourth, and fifth somites of the pleon are posteriorly 

 elevated. In all other points this species agrees with the type. 



