688 THE VOYAGE OF H.M.S, CHALLENGER. 



oplithalmopod, and the third joint, which is subequal with the second, reaches to the 

 extremity of the rostrum and terminates in two short flagella. 



The second pair of antennae carries a long flagellum, but it is broken off a little behind 

 the distal extremity of the scaphocerite, which reaches to the length of the peduncle of 

 the first pair, is rounded at the extremity and fringed with hairs, the outer angle being 

 furnished with a strong tooth. 



The mandibles are without a synaphipod. 



The first pair of pereiopoda (fig. 3k) is long and slender ; the meros is long, the 

 carpos and propodos gradually enlarge and then as gradually decrease in thickness 

 anteriorly to that of the dactylos, which terminates in a long straight unguis, the base of 

 which bears a hair or two. The second pair (fig. 3/) is short, robust, and chelate ; the 

 carpos and propodos continuously enlarge at first and as gradually decrease to the 

 extremity of the dactylos and form a long ovate chela, the fingers of which are about 

 half the length of the palm of the propodos. The third (fig. 3m) and fourth pairs resemble 

 each other ; they are short, and terminate in a biunguiculate dactylos that is about one- 

 third the length of the propodos. The fifth pair (fig. 3o) is very long and slender, 

 reaching anteriorly as far as the extremity of the ophthalmopoda. It is remarkable 

 for the large size of the coxal joint, which is broad at the base but rapidly narrows to 

 the diameter of the basis, and generally lies directed forwards. 



The pleopoda are all biramose, the posterior pair not being longer than the 

 telson. 



Observations. — This specimen is one of interest from the remarkable state of transition 

 which it exhibits. It is evidently a young animal that is passing from one stage to 

 another, the change almost corresponding in degree to a metamorphosis. The antennae 

 and other appendages are seen in a higher state of development within the older skin 

 that is about to be shed, but the fifth pair of pereiopoda, which in the adult state 

 terminates in a biunguiculate dactylos, is inclosed within an older case that is produced 

 to a long and slender point, more than four times its length, and fringed at the extremity 

 on the concave side with a series of small reversed teeth. 



Diaphoropus longidorsalis, n. sp. (PI. CXVII. fig. 4). 



Carapace long, cylindrical, carrying a short, pointed rostrum. Frontal margin with- 

 out an antennal tooth ; fronto-lateral angle produced to a small tooth. 



Pleon having the five anterior somites subequally long ; sixth somite as long as the 

 two immediately preceding. 



Telson nearly as long as the sixth somite. 



Ophthalmopoda short and thick, but twice the length of the rostrum. 



First antennae twice the length of the oplithalmopod. 



