REPORT ON THE CRUSTACEA MACRURA. 837 



Habitat.— Station 184, August 29, 1874; kit. 12° 8' S., long. 145° 10' E.; depth, 

 1400 fathoms; bottom. Globigerina ooze; bottom temperature, 36°. One specimen, 

 male. Trawled. 



This species differs from Hymenodora mollis in having the dorsal crest and rostrum 

 more compressed laterally, and anteriorly elevated to a horizontal line with the dorsum. 

 The denticles are very minute, fewer in number, and more distantly separated from each 

 other, and in our specimen have the appearance of being worn. The orbit exists as a 

 well-defined notch without any tooth at the outer canthus, the tooth beyond, which is 

 the first antennal tooth, is apparently worn and exists as a rudiment only, whereas the 

 second antennal tooth is short and more clearly defined, and projects anteriorly outwards 

 from the frontal margin ; jwsteriorly the lateral margin overlies the first somite of the 

 pleon, and is reduced to an extreme degree of tenuity. 



The first two somites of the pleon are dorsally rounded and smooth, and are divided 

 into an anterior and a posterior section ; the lateral plates are of extreme tenuity and are 

 broadly developed, that of the second overlapping the first. The third somite is dorsally 

 slightly carinated, and posteriorly produced to a sharp tooth ; the fourth, fifth, and sixth 

 are feebly carinated and terminate abruptly, or in the most minute tooth-like projections. 



The ophthalmopoda are shorter than the rostral projection, pyriform, and but little 

 if at all compressed ; the tubercle on the inner surface is reduced to a minimum, and 

 situated close to the ophthalmus. 



The first pair of antennae has the peduncle short, but longer than the rostrum ; the 

 first joint is rather deeply excavate to permit the ophthalmopod to rest in the hollow ; 

 the second and third joints are very short and cylindrical, and support two unequal 

 flagella of the ordinary character in the species of this genus. The stylocerite is nearly 

 as long as the first joint and sharp-pointed. 



The second pair of antennae has the scaphocerite slightly tapering, of great tenuity, 

 and furnished with a small denticle on the outer distal extremity, the two joints of the 

 peduncle that succeeds the articulation of the scaphocerite are unequal in length, the 

 distal being the longer and more robust. The flagellum is wanting. 



The mandible and oral appendages have not been examined in this species, but I 

 assume they are generic in condition. 



The first pair of gnathopoda resembles the same organ in Hymenodora duplex, but the 

 basecphysis is wanting, which I attribute to injury, inasmuch as the muscles that move 

 it are present ; the coxa supports a mastigobranchia of extreme tenuity, and attached to it 

 is a small podobranchial plume. 



The second pair of gnathopoda is broken off at the distal extremity of the ischium. 



The first two pairs of pereiopoda are chelate. The first and a portion of the fifth are 

 the only parts preserved in the solitary specimen. 



