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



Eupagurus tristanensis, u. sp. (PL VII. fig. 5). 



Characters. — The anterior portion of the carapace is smooth, with the median frontal 

 process moderately prominent, and subacute, the lateral projections less strongly marked ; 

 the posterior portion is entirely membranous. 



The ocular peduncles are stout, with the cornese slightly dilated ; the ophthalmic 

 scales have the terminal portion slender and acute. The antennal i^eduncle slightly 

 exceeds the eye-stalks in length ; the acicle is slender and curved, reaching the middle of 

 the ultimate joint, its inner margin slightly pubescent ; the external prolongation of the 

 second joint is short, extending only as far as the middle of the penultimate joint. The 

 antennular peduncle exceeds the eye-stalk by more than half the length of the terminal 

 joint, which broadens out towards its distal end. 



The chelipedes are unequal and of moderate size, the terminal joints are armed with 

 acute spinules. The right chelipede has the meral joint trigonal, the upper and anterior 

 border possesses three minute spinules, and a few spinules are also present on the lower 

 surface and outer border ; the carpus is more than two-thirds the length of the propodus, 

 and its upper surface is uniformly covered with projections which become distinct!}' 

 spiniform on the inner margin, the outer surface is smooth and of considerable vertical 

 extent ; the proj^odus is of almost the same breadth as the carpus, and the spinules on 

 its upper surface are arranged in longitudinal rows, the margins are distinctly spinulous ; 

 the ujjper surface of the dactylus possesses a median row of tubercular spinules, and its 

 tip is folded under that of the immobile finger. The left chelipede has the merus 

 unarmed, with the exception of a few minute spinules on the lower border ; the carpus 

 has two rows of spinules on its upper surface, with a groove-like portion between, and 

 the outer surface is granular ; the propodus bears a central carina on the upper surface, 

 surmounted by a row of spinules, and elsewhere it is obscurely tubercular ; the dactylus 

 is unarmed. The ambulatory limbs are smooth, a few indistinct spinules alone existing 

 on the propodi of the first pair ; the dactyli are canaliculate and but little curved, they 

 exceed the propodi in length, and their lower border is fringed by a series of delicate 

 corneous spines. 



The penultimate abdominal segment is divided by a transverse constriction, and the 

 ultimate segment is obscurely four-lobed. 



Length of body 10 mm., of right chelipede 11 mm., of left chelipede 9 mm., of third 

 left leg 13'5 mm., of ocular peduncle 2 mm. 



This species is distinguished by its small size and the armature of the right 

 chelipede. 



Habitat. — Station 135c, oif Nightingale Island, Tristan da Cunha ; depth, 110 

 fathoms. A male specimen in a shell of Murex [Pseudomurex) aedonius, Watson. 



