REPORT ON THE CRUSTACEA MAC'RURA. 377 



dorsally smooth except the posterior, which is furnished at the posterior margin with a 

 small toot!;. The infero-lateral margin of these somites is produced to a sharp tooth, 

 which gradually increases in length posteriorly, the anterior three being directed forwards 

 and the others obliquely backwards ; in the median ventral- line is a deep, longitudinally 

 compressed, rounded cusp. The sixth somite is about equal in length to the two preceding, 

 and posteriorly terminates on the dorsal surface in a small tooth. 



The telson is about as lung as the sixth somite, and terminally forked with two 

 small teeth. 



The ophthalmopoda are fungiform and subequal in length to the first joint of the 

 peduncle of the first pair of antennae. 



The first pair of antennae has the peduncle three-jointed and about as long as the 

 carapace ; the first joint is longer than the second, and is enlarged at the base, which is 

 furnished with a sharp anteriorly directed tooth and encloses the otocyst, and the second 

 a little shorter than the third, which supports a multiarticulate flagellum that is as long 

 as the peduncle, and a small uniarticulate secondary ramus. 



The second pair of antenna? is broken off at the extremity of the peduncle ; it 

 supports a scaphocerite with parallel margins, and nearly as long as the peduncle of the 

 first pair, and is armed with a long and slender tooth near the distal extremity. The 

 basal joint of the peduncle is also armed with a strong tooth at the outer distal angle, 



The first pair of gnathopoda is formed after the type of the adult organ, as is also the 

 second pair. 



The pereiopoda that are developed have lost their lateral ecphyses, and have not 

 attained the form of the' minute chelae, at the extremity of the second and third pairs, 

 which are present in the mature form, while the fourth still exists as a small saccular 

 appendage, and the fifth is very minute and rudimentary. 



The pleopoda have attained much of their adult character, but their inner branch has 

 not yet reached its normal proportions. 



The posterior pair is long, slender, and slightly curved, and is armed with a strong 

 tooth near the middle of the outer margin of the outer branch, while the inner is narrow, 

 pointed, one-fourth shorter, and fringed with hairs. 



Length, 6 mm. 



Habitat.— The Western Pacific Ocean. (Labelled " Y." (? young) " Sergestes V." 

 in Suhm's series.) 



This specimen corresponds in general characters wdth that given on PI. LXX\ 1. fig. i!. 

 and it differs only in those temporary features which disappear with age. 



It has the rostrum shorter and free from serrature along the margins. It is smooth 

 ami does not reach as far as the extremity of the peduncle of the first pair of 

 antennas. The tooth or spine that stands above the first pair of antennae is reduced in 



(ZOOL. CHALL. EXP. — PART LII. 1886.) Fff 48 



