96 BRIGHTWELL, ON DIATOMACE.E. 



This very beautiful species has occurred occasionally, but 

 only in a broken state. 



30. Cyclotella stylor'um, n. sp. — Valve with the central circle 

 punctate, and with styliform rays diverging from it, each 

 ending near the margin in a large circular head. Diameter, 

 •019 to 03, the former the common size. (PL VI, fig. 16a, 

 side view; b, front view.) River Rohelle, Sierra Leone. 

 Common. 



31. Cyclotella radiata, n. sp. — Valve, end view, with simple, 

 strongly-marked radii, about 11 in "001. Front view, with 

 the ends of the radii appearing as puncta. Diameter, '018 

 to -023. (PL VI, fig. 11a, end view; b, front view.) Shell 

 cleanings, West Indies. 



As many as ten frustules have been found in union, leaving 

 it doubtful whether this may not belong to the next genus. 



32. Orthosira oceanica (Endictya oceanica), Ehr.— Dia- 

 meter, -027 to -035. (PL VI, fig. 16a, end view; b, front 

 view.) Common in various gatherings, but not yet recog- 

 nised as British, unless the valve figured by Dr. Gregory 

 (Clyde Diat,, pi. ii, fig. 47) be this form, which appears pro- 

 bable. A large and coarse species : it is seldom that more 

 than two or three valves are found united, and these are not 

 of the same frustules, so that the union by the connecting 

 membrane Avould seem to be the strongest. 



33. Stephanogonia polygona, Ehr. — Valve, with centra] 

 portion impunctate and much elevated, united to the margin 

 by an indefinite number of rays, the spaces between which 

 are sometimes found to be verv faintly punctate. Diameter, 

 •015 to -025. (PL V, fig. 8a, side view ; b, front view.) 



Richmond Earth, Virginia, N. A. Common. 

 Prom the peculiar form of this interesting species, it 

 happens that it is seldom seen in any but an oblique position. 



