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



armed with two short solitary spinules, placed longitudinally on each side, and ter- 

 minating in two long lateral and one central spine. 



Observations. — This species bears a close relationship to Brachycarpus savignyi, 

 which was taken at Bermuda, also in comparatively shallow water. It differs, however, 

 in several points of specific value, notably in the form of the dactylos of the posterior 

 pereiopoda, which in this species is single-pointed, while in Brachycarpus savignyi it is 

 bifid. The fingers of the large chela in Brachycarpus savignyi are broad and gaping, 

 the gap containing tubercles and a mass of hairs, while in Brachycarpus aadouini the 

 fingers impinge in their entire length, and are devoid of hairs or tubercles. 



Nematocarcinus, A. Milne-Edwards. 

 Nematocarcinus, A. Milne-Edwards, Ann. d. Sci. Nat., sor. 6, torn. ix. p. 14, 1884. 



Dorsal surface of the carapace and pleon continuously smooth and even. Carapace 

 anteriorly produced to a laterally compressed rostrum that is finely and more or less 

 abundantly serrate on the upper surface and smooth on the lower, or at most armed with 

 very small teeth. Frontal margin furnished with one tooth, corresponding with the 

 outer angle of the first pair of antennae, and a second at the fronto-lateral angle, from 

 whence the inferior margin immediately recedes. 



The ophthalmopoda are short, and the ophthalmus globular. 



The first pair of antennas has the first joint deeply excavate, and furnished with 

 a stylocerite ; the second and third joints are short and robust, terminating in two 

 extremely long and slender flagella, the outer of which is stout near the base. 



The second pair of antennas carries a long scaphocerite, and terminates in an extremely 

 long and slender flagellum. 



The mandibles have the psalistoma and molar processes distinct, and carry a two- 

 jointed synaphipod. 



The first pair of gnathopoda has the terminal joints reflexed, and carries a long 

 basecphysis and a well-formed mastigobranchial plate. 



The second pair of gnathopoda terminates in a long spatuliform joint, and is furnished 

 with a long basecphysis. 



The first two pairs of pereiopoda are slender and perfectly chelate, the second being 

 much longer than the first, and having the carpos about four times the length of the 

 propodos. The three following pairs are extremely long, and are remarkable for the 

 peculiar overlapping articulation between the ischium and meros, in having the carpos 

 many times longer than the propodos, and terminating in a short and sharp dactylos. 



The telson is subequal with the inner branch of the rhipidura. 



This genus is remarkable for the great length of the antennas, more especially those of 

 the first pair, which are frequently three or four times the length of the animal ; and the 



