of the Fishery Board for Scotland. 



Fio. 1. — Chcetoceros borealis, var. 

 solitaria, 500 tm. 



with a spire of conspicuous spines. Awns of the lower valve somewhat 

 diverging. Cell-contents: scattered chromatophores, also in the awns. 

 Long, axis, 0'02 ; sag. axis, 0*015; trans, axis, 0'012 mm. 



This species may be the same as C. volans, Schiitt (Ber. D. Bot. Ges., 

 1895, Bd. XIII. fig. 20), but in the fig. of 

 Schiitt the awns of the upper valve arise 

 near the margin, and, besides, there is no 

 description of the awns, so I cannot, with- 

 out original specimens, identify them. C. 

 currens was met with this summer in the 

 seas around Spitsbergen and Beeren 

 Eiland. 



Choetoceros decijpiens, CI. (D. f. Arct. S., 

 PI. I. fig. 5). Of this species, so abundant 

 in the middle Atlantic, some few specimens 

 only were found. 



Choetoceros peruvianas, Btw. (PI. fig. 

 7 ) (M.J. IV., PI. VII. figs. 16-18; and 

 VI., PI. VIII. figs. 9, 10). This species is 

 nearly related to C. currens, but much 

 coarser, and differs especially by the awns, 

 which are coarsely transversely striate (striae 

 21 in 0*01 mm.), and carry a spiral of coarse 

 spines. 



C. peruvianus belongs to the warmer seas. 

 1 know this form from Ascension, the 

 Mediterranean, and Java. 



Corethron hystrix, Hensen (PI. fig. 

 15). Frustule very thin and membran- 

 aceous, cylindrical, short, with very convex valves. Long, axis, 0*04 

 to 0 07; diam., 0*02 to 0-03 mm. Both valves at their basis with a 

 circlet of straight, simple awns, all in the same direction, or about 

 45° from the longitudinal axis ; upper valve besides with a number of 

 exceedingly delicate hairs, thickened at their ends. Cell-contents : 

 numerous linear chromatophores, which radiate from the nucleus along 

 the inside of the frustule. Nucleus near the connecting zone. 



This species is nearly related with a form from the Antarctic Ocean, of 

 which Mr Comber sent me specimens ; also that form has, as Mr Comber 

 pointed out, between the awns, hyaline hairs, which end in hooks, 

 but they are much stronger than in C. hystrix. 



C. hystrix was found only in a small number of specimens. I have 

 also observed it this summer in samples from Beeren Eiland, and in the 

 end of October in the middle of the North Sea. It seems to be a char- 

 acteristic, but rare, form of the Atlantic plankton. 



Coscinodiscus anguste-lineatus, A. Schm. (Atl., PI. LIX. fig. 34) var. 

 Some few valves were found in the mixed sample. Diam., 0*01 to 0*03 

 mm. Margin with a row of apiculi (5 in 0*01 mm.). Kows of cellules, 12 

 to 18 in 0-01 mm. 



Coscinodiscus curvatulus, Gran. var. Some few valves in the mixed 

 sample. Diam., 0*035 to 0*055 mm. Margin with a row of apiculi (2-3 

 in 0*01 mm.) and a pseudonodule. Rows of cellules almost straight, 6 to 7 

 in each bundle, and about 6 in 0*01 mm. 



Coscinodiscus minor, Ehb. var. In the mixed sample some few valves 

 were found of a form resembling A. S. Atl., CX1II. fig. 10, and LIX. fig. 8, 

 but of extremely small size, 0*01 mm. only in diameter. Cellules about 

 12 in 0*01 mm., larger in the middle and smaller at the margin, which 

 is striate (striae about 20 in 0*01 mm.). 



