REPORT ON THE CRUSTACEA MACRURA. 73 



Arctus pygmsBus, n. sp. (PL X. fig. 4). 



Female tuberculated on the cardiac region. Upper lateral margin of the branchial 

 region marked with a row of tubercles. Somites of the pleon transversely furrowed, with 

 anterior and posterior margins ornately scalloped. 



Length, 22 mm. (CT875 in.). 



Habitat. — Station VIIp, off Gomera, one of the Canary Islands, February 10, 1873 ; 

 lat. 28° 35' N., long. 16° 5' W.; depth 78 fathoms; bottom, volcanic sand. 



Carapace longer than the width between the anterior extra-orbital angles. Sub-rostral 

 point small ; gastric and epigastric slightly elevated ; the latter is continuous with a 

 series of flattened tubercles that form the central ridge, broken only by the imperfectly 

 defined cervical sulcus. The lateral ridges are strongly marked and elevated, commencing 

 at the inner canthus of the orbit, and continuing unbroken to the cervical sulcus, 

 posterior to which the ridge is continued in the form of a series of double tubercles to 

 the latero-posterior margin of the carapace. The anterior extra-orbital angles are 

 prominent, but in close contact with the wall of the orbit ; the lateral margin shows no 

 evidence of the cervical depression. The carapace is adorned by a number of flattened 

 tubercles chiefly aggregated between the branchial and cardiac regions. On the former 

 region they exist only as a row along the inferior margin, while on the cardiac border 

 they traverse the width of the dorsal surface as two double rows separated by a narrow 

 post-cardiac sulcus. 



The pleon is smooth, with scarcely any median dorsal elevation, on each side of 

 which an arborescent line of depression traverses the surface from the coxal margin to 

 the central ridge, dividing the somite into two unequal portions, and terminating on the 

 anterior margin near the centre, leaving between the two extremities a longitudinal 

 ornamentation of flattened semicircular plates. 



The eyes are round and near the lateral margins of the carapace. 



The first pair of antennae has the first joint tolerably robust, the others slender. 



The second pair of antennae has five cusps on the anterior and two small ones on the 

 inner margins, copiously fringed with plumose hairs. On the inferior surface of the 

 externo-posterior margin is a row of small cell-like organs. The second joint has the 

 anterior margin dentate and two stronger teeth on the outer margin ; the oblique ridge 

 is strongly prominent, but does not extend so far as the anterior margin of the terminal 

 joint. 



The first pair of pereiopoda is robust; the three succeeding are sub-equal and 

 cylindrical, without any enlargement of the propodos ; the fifth pair is unfortunately 

 broken from the basal joint in our unique specimen. 



The first pair of pleopoda is, as in larger adult forms, foliaceous, and the succeeding 

 pairs have one branch small and leaf-like, and the other rigid and styliform. 



(ZOOL. CHALL. EXP. PART LII. — 188G.) Fff 10 



