18(3 THE VOYAGE OF H.M.S. CHALLENGER. 



some invertebrates. In specimens so long macerated in alcohol, it is impossible to speak 

 positively of such structures, but I believe that the function of the thick wall is to secrete 

 a digestive fluid. It should be observed, also, that this soft cell layer may easily 

 be scraped off, leaving the outer thin membranous sac of the digestive cavity. On 

 the floor of the cavity was found a mass containing minute isopods and larvae of 

 brachyurans. 



Marion Island ; 50 to 75 fathoms. The following three places in the Kergulen Islands : 

 — Christmas Harbour, 120 fathoms; Balfour Bay, 20 to 60 fathoms; Eoyal Sound, 25 

 fathoms. Station 151. — February 7, 1874 ; off Heard Island ; 75 fathoms; mud. Station 

 313.— January 20, 1876 ; lat. 52° 20' S., long. 68° 0' W. ; 55 fathoms; sand. Station 

 314.— January 21, 1876 ; lat. 51° 36' S., long. 65° 40' W. ; 70 fathoms; sand. Station 

 320.— February 14, 1876 ; lat. 37° 17' S., long. 53° 52' W. ; 600 fathoms; hard ground, 



Ophiacantha, bidentata, Ljn., Dr Goes Oph. p. 652 ; Lym., Bull. Mus. Comp. Zool., 



vol. v., part 7, p. 149, 1878. 



Asterias bidentata, Retz., Diss., p. 33, 1805. 



Ophiura Retzii, Nilsson, Collectanea Zoologise Scandinavica?, p. 15, 1817. 



Ophiacantha spinulosa, Mull. & Tr., Syst. Ast., p. 106, 1842; Ltk. Addit. ad Hist., part 1, 



p. 65, pi. ii. fig. 14; Lym., 111. Cat. Mus. Comp. Zool., No. i. p. 93, figs. 6, 7. 

 Ophiocoma arctica, Mull & Tr., Syst Ast., p. 103. 

 Ophiacantha gronlandica, Mull. & Tr., Wieg. Archiv, p. 183, 1844. 

 Ophiocoma echinulata, Fbs., Suth. Journ. Voy. Baffin's Bay, vol. ii. App., p. ccv., 1852. 



Dr. Ljungman showed me at Stockholm the original of Retzius, which is, without 

 question, this species. 



Station 45.— May 3, 1873 ; lat. 38° 34' K, long. 72° 10' W. ; 1240 fathoms; mud. 

 Station 46.— May 6, 1873; lat. 40° 17' N., long. 66° 48' W. ; 1350 fathoms; mud. 

 Station 49.— May 20, 1873; lat. 43° 3' N., long. 63° 39' W. ; 83 fathoms; gravel, 

 stones. 



Ophiacantha imago, Lym. (PI. XXV. figs. 4-6). 



Ophiacantha imago, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 139, pL x. figs. 275, 276, 

 1878. 



Disk regularly set with small, short thick stumps, each bearing a crown of blunt 

 thorns ; tentacle scales small and pointed ; six short opaque, cylindrical, scarcely thorny 

 arm spines. 



(Type specimen from Kerguelen Islands.) Diameter of disk 8 mm. Length of arm 

 37 mm. Width of arm without spines 1*6 mm. Seven short, stout, blunt, close-set 

 mouth papillae ; the innermost are a little the largest. Four flat, rather thick teeth , all 

 squarish, except uppermost one, which is pointed. Mouth shields small, of a rounded 



