374 THE VOYAGE OF H.M.S. CHALLENGER. 



flagellurn that appears not to be multiarticulate, and a long and narrow scaphocerite that 

 is not armed with a tooth on the outer side, but is tipped with long hairs at the 

 extremity, and has others that gradually decrease in size from the extremity and 

 disappear about halfway down. 



The gnathopoda and pereiopoda are advanced in development and biramose, but still 

 in a saccular condition. 



The pleopoda are also considerably advanced, but saccular in form, except the sixth 

 pair, which is long and narrow, with the margins parallel and the branches equal. There 

 is no tooth on the outer margin of the external plate, but its place is taken by a small hair 

 or spine, one-fifth distant from the basal articulation, from which point the outer margin 

 is fringed with short hairs, that increase in length to the apex ; the inner side of this as 

 well as both sides of the inner plate are also similarly adorned. 



Length, 3 mm. (0'12 in.). 



Habitat. — Samboangan, Philippines. 



Acanthosoma Isevirostratis (PI. LXV. fig. 2). . 



Carapace about one-third the length of the body of the animal (a little longer than 

 shown in the figure). Rostrum scarcely as long as the carapace, smooth and unarmed. 

 The outer orbital angle carries a long serrate process (which is not clearly shown in 

 the plate as being distinct from the first antenna), a second stands on the antero-lateral 

 angle, another smaller one exists between it and the mandibular attachment, or over 

 it, and a fourth projects from the lateral margin, near the branchial region. 



The pleon has each somite dorsally armed with large spinous processes, that stand 

 anterior to the posterior margin, and are all strongly but varyingly spinous ; the largest 

 is on the fourth somite, and the smallest on the sixth. The second, third, fourth, and 

 fifth somites are also armed at the infero-lateral margins with strongly serrate spines, but 

 the first somite is smooth and free from ornamentation, and the sixth is furnished with 

 a small smooth denticle. The ventral surface has in the median line a longitudinally 

 narrow, rounded protuberance on the five anterior somites. 



The telson is long, slender, forked, and distally armed with a few tooth-like processes. 



The ophthalmopoda are shorter than the rostrum and fungiform, the ophthalmus 

 being; more than twice the breadth of the stalk. 



The first pair of antennae is longer than the rostrum, and consists of two joints, the 

 basal being long, slender, and reaching considerably beyond the extremity of the rostrum, 

 the second obliquely attached to the extremity of the first, and about one-third of its 

 length, and at its base is the rudiment of the second ramus. 



The second pair of antennae has a basal joint, and supports a slender flagellum that 

 does not reach beyond the extremity of the first pair, and a narrow scaphocerite with 



