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



and not in a good state of preservation), and fifteen specimens of the solitary form (the 

 largest is 3 "3 cm. in length and 2-3 cm. in breadth). 



(18.) April 13, 1876; Station 352, North Atlantic; lat. 10° 55' 0" N., long. 17° 46' 

 0" W.; surf. temp. IT'I ; forty-three specimens of the aggregated form (several small, the 

 rest of medium size, 2 "3 cm. in length), and one specimen of the solitary form (fragment). 



(19.) April 26, 1876 ; North Atlantic; lat. 16° 49' 0" N., long. 25° 14' O" W. ; surf, 

 temp. 7 3° "2 ; ten specimens of the aggregated form (fairly large). 



(20.) April 29, 1876; North Atlantic; lat. 18° 8' 0" N., long. 30° 5' 0" W. ; surf, 

 temp. 74° ; ten specimens of the solitary form (r4 cm. to 2*2 cm. in length). 



(21.) May 7, 1876 ; North Atlantic ; at night ; lat. 34° 22' 0" N, long. 34° 23' 0" W. ; 

 surf. temp. 67°'5 ; eight specimens of the aggregated form. 



(22.) Collected during the cruise of H.M.S. "Triton" in August 1882; in the 

 North Atlantic, to the north-west of Scotland ; one specimen of the solitary and one 

 uf the ao-gregated form. 



The specimens collected by the Challenger vary considerably in size in both forms 

 of the species. Taking the aggregated form first, we find that the hundred specimens 

 collected in the South Atlantic, on March 9, 1876, vary in length from 5 mm. to 4 cm. 

 The greater number of them are about 2 cm. in length. The largest specimens are 

 those obtained in the South Pacific, on October 20 and November 6, 1875. They 

 measure 6 cm. in length by 2 cm. in greatest breadth. 



The other dimensions of the specimens from the South Pacific, on November 6, 

 1875, are as follows : — 



From the anterior end of the body to the middle of the dorsal junction of 



the muscle bands, . . . . . . .25 cm. 



From the middle of the dorsal junction of the muscle bands to the posterior 



end of the visceral mass, . . . . . . 2'0 cm. 



From the posterior end of the visceral mass to the posterior end of the body, 1 '5 cm. 



Several of the specimens from Station 152, in the Antarctic, measure over 5 cm. 

 in length by nearly 2 cm. in greatest breadth. In some of these the anterior and 

 posterior tapering processes of the body are relatively very much shorter than in the 

 specimen figured by Traustedt,' and the posterior one has the test thickened, and 

 provided with a sharp ridge running along each side of the dorsal surface. In some of 

 the specimens these ridges are toothed or finely serrated (PI. VI. fig. 5). In a few of 

 the specimens there are also a ventral and two more or less complete lateral ridges, 

 giving the body an angular or somewhat prismatic appearance. In fact, the shape of 

 the body, and especially the proportion of the anterior and posterior pointed ends, 

 seems liable to a great deal of variation. 



The specimens obtained in the North Atlantic, on April 26, 1876, have their 

 ends bifurcated in place of being pointed (see PI. VI. fig. 6), and some have the 



' Bidrag til Kundskab om Salperne, Tab. ii. fig. 31. 



