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



Habitat— Station 144a, December 26, 1873 ; lat. 46° 48' 0" S., long. 37° 49' 30" E.; 

 off Marion Island ; depth, 69 fathoms ; bottom, volcanic sand. Sixty-seven specimens ; 

 males and females, the former apparently predominating. Dredged. Some of the 

 females were taken with ova attached, in which the embryo was far advanced in develop- 

 ment. 



Station 145, December 27, 1873 ; lat. 46° 43' 0" S., long. 38° 4' 30" E.; off Prince 

 Edward Island; depth, 140 fathoms; bottom volcanic sand. Three specimens ; males. 

 Dredged. 



Station 315, January 26, 1876; lat. 51° 40' S., long. 57° 50' W.; off the Falkland 

 Islands; depth, 12 fathoms; bottom, sand, gravel. One specimen ; male. Dredged. 



The carapace is laterally smooth and free from any denticular ornamentations, 

 excepting those which exist on the frontal crest and rostrum, and those on the frontal 

 margin which mark the orbital and antennal regions. The dorsal surface culminates in a 

 frontal carina that projects as a rostrum (fig. 2), which is armed on the upper surface with 

 from eight to twelve teeth, the posterior situated on the gastric region and the anterior 

 being subapical. The larger number of teeth appears to occur in the males and the 

 smaller in the females. On the under surface there are three large teeth, the posterior 

 being the largest, lying in advance of a deep excavation for the reception of the 

 ophthalmopoda. The outer canthus of the orbit is defined by a tooth, and beyond 

 it there exists an antennal tooth, from which the frontal margin of the carapace descends 

 slightly forwards and forms a slightly projecting tooth at the junction with the inferior 

 margin ; the latter recedes posteriorly and downwards to form the branchial chamber. 



The somites of the pleon are smooth, unarmed, and subequal in length ; the third is 

 slightly arcuate, rather more so in the males than in the females. The fifth somite is the 

 shortest, and the sixth slightly the longest ; the latter has the lateral walls confluent with 

 the ventral surface of the somite, and is furnished at the postero-inferior angle with a 

 movable spine (v) that, so far as my experience goes, is unique. It is broad and flat at the 

 base and tapers to a sharp point ; it appears to spring from a hollow space in the margin 

 rather than being directly attached to it, it is slightly movable and fringed with ciliated 

 hairs on the anterior margin only. 



The telson (z) is rigid, tapers to a point, and is armed on each side of the dorsal surface 



