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



peduncle of the first pair, but not quite to the extremity of the rostrum, and terminates 

 in a flagellum about once and a half as long as the animal. 



The dactyii of the anterio rthree pairs of pereiopoda are long and slender. 



The pleopoda are moderately slender and elongated. 



Habitat— Station 170, July 14, 1874; lat. 29° 55' S., long. 178° 14' W.; near the 

 Kermadec Islands ; depth, 520 fathoms; bottom, volcanic mud; bottom temperature, 43°"0. 

 Three specimens. 



Length, largest female 107 mm. (4 - 25 in.), smallest male 51 mm. (2 in.). Trawled. 



Station 171, July 15, 1874 ; lat. 28° 33' S., long. 177° 50' W.; north of the Kermadec 

 Islands; depth 600 fathoms; bottom, hard ground; bottom temperature, 39°"5. One 

 specimen; female. Length 150 mm. (6 in.). Trawled. 



Station 194, September 29, 1874; lat. 4° 34' S., long. 129° 57' 30" E.; off Banda 

 Island ; depth, 200 fathoms ; bottom, volcanic mud. One specimen ; female. Length, 

 55 mm. (2 in.). 



This species corresponds so closely in general appearance with Duvernoy's figure * of 

 Aristeus antennatus, Risso, that it was only proved not to be a variety by comparing it 

 with Risso's figure, 2 and by careful consideration of the details of the specimens in this 

 collection. In Risso's figure it is without eyes, but at page 97 he says that " Les yeux 

 sont gros, noirs, places sur les courts pedicules ;" he also says that " les antennes 

 superieures, ingalement bifides," and figures them subecpml, slender, and not longer 

 than the rostrum, and has the dorsal surface of the pleon smooth, " dont les deux 

 (segmeros) derniers sont carenes." Duvernoy represents the eyes as standing on a long 

 peduncle, but smaller in proportion to the diameter of the stalk than is the case in our 

 specimens. He also figures the larger flagellum of the first pair of antennae as being 

 longer than that of the second, but this is probably an error in drawing. He also repre- 

 sents the dorsal surface of the pleon as being smooth, and the posterior margins of the 

 fourth and fifth somites as produced in the median line to a point, whereas in the 

 Challenger specimen the two somites are not so produced, but elevated into a small and 

 distinct carina that terminates in a small point on the fifth and sixth somites, and in 

 some specimens on the fourth also. 



This species differs from Aristeus armatus, which it much resembles, in having the 

 rostrum proportionally shorter, the teeth on the crest rather smaller, and none on the 

 third somite of the pleon, where in Aristeus armatus it is very large, as are also those 

 on the fourth and fifth somites, whereas in Hemipenwits semidentatus there is only a 

 small carina which terminates almost abruptly. 



The branchiae in the Challenger specimens correspond with those of the other species 



1 Ann. d. Sci. Nat, t. xv., 1841. 



2 Hist. Nat. Crust, des Environs de Nice, p. 96, pi. ii. fig. 6. 



