25S DISCOVERY REPORTS 



diameter of the organism. The loculi were fewer in number, and were usually con- 

 siderably inflated. 



An oceanic species with a wide distribution occurs in European waters, but is found 

 in great numbers in tropical and subtropical seas. 



Observed at Sts. 260, 261, 262, 263, 264, 265, 289, 424, 425, 427, 428, 431, 432, 433, 

 434, 435, 436, 437, 438, 439, 440, 449, 450, 451, 452, 673, 675, 684, 690, 1373, 1376, 

 1572, 1574, 1575, 1581, 1583, 1584; WS621, 622, 623, 629, 630, 631, 640, 641, 642, 

 643, 644, 645, 666, 705, 706, 715, 716. 



Planktoniella formosa (Schimper ex Karsten) Karsten. 



Karsten, 1928, p. 146, pi. 218. 

 Valdiviella formosa Schimper ex Karsten. 

 Karsten, 1907, p. 369, pi. 39, fig. 12. 



Cells discoid, solitary. Valves flat or nearly so, slightly convex towards the margin. 

 Valves covered with faint cellulation, somewhat similar to that of Coscinodiscus excen- 

 tricus. Valves surrounded by a wide and strongly developed extravalvar wing-like ex- 

 pansion, similar to that of Planktoniella sol, but differing from it in that, in P. formosa, 

 the strengthening radial ribs which divide the wing into chambers are straight, rigid, 

 frequently wide, and much more numerous than in P. sol, fifty to seventy ribs being 

 present. The radial ribs do not directly join the margin of the valve portion, but appear 

 to be attached to a strong circular frame, outside the margin of the valve proper. The 

 bases of the individual chambers are neatly curved or rounded, and not angular as in 

 P. sol. The chambers are open upon the outer margin, and bear radial striation. This 

 radial striation makes the wing-like membrane rigid, so that it is observed neither in a 

 state of collapse nor of extreme turgidity, as in the case of P. sol. Chromatophores : 

 numerous small rounded or oval plates. Diameter of valve 40-54/x ; total diameter 

 including extravalvar expansion 80-1 10/1. 



Observed at St. 440. 



Genus Gossleriella Schiitt 

 Schtitt, 1893 



Gossleriella tropica Schiitt. (PI. XII, fig. 1.) 



Schiitt, 1893, p. 20, fig. 7. 



Karsten, 1907, p. 368, pi. 40, figs. 14-17. 



Hustedt, 1929, p. 500, fig. 280. 



Cells discoid, usually solitary, but sometimes forming short chains. Valves convex, 

 but sometimes slightly flattened. Valves without visible structure, but furnished with a 

 marginal corona of stout bristles which proceed from small nodules or thickenings 

 around the edge of the valve in the valvar plane. Between each stout bristle is a number, 

 usually three to six, of finer bristles which are often a little shorter than the stout 

 ones. The valve margin may be furnished with three distinct coronas of bristles. Upon 

 some specimens a corona of bristles was observed proceeding from the centre of the 

 valve numerous short spines are dotted frequently over the remainder of the valve. 



