224 



HARDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, 1S69. 



rally so common as those of a linear form ; the 

 following may, however, often be detected. 



Fig. ig:5. Asterionclla Bleukleyii. 



Coschwdiscus ovalis (fig. 194).— Valve broadly 

 oval : the markings are very fine, and require a good 

 glass to resolve them ; they consist of tine dots, 

 radiating from the centre of the valve : valves will 

 frequently be found with conspicuous dots (? spines) 

 round the margin. 



Figr. 194. Coscino discus ovalis, Fig. 195. Coscinodiscus nitidus, 

 X 400. X 400. 



Coscinodiscus nitidus (fig. 195). — A. small form, but 

 easily distinguished by its distant and brilliant dots, 

 slightly decreasing in size as they approach the 

 centre. 



Coscinodiscus excentricus (fig. 196). — Small valves 

 of the species occur in the sand-gatherings: the 

 observer will readily recognize them by the excen- 

 tric arrangements of the markings and the spinous 

 margin. 



Fig. 196. 

 Actinoptychus undulatus. 



Fig. 197. Auliscus eculptus. 



Actinoptychus undulatus (fig. 196). — A species very 

 variable in size, but easily detected by its conspicu- 

 ous radiating line: the spaces between each division 

 are alternately elevated and depressed ; the mark- 

 ings consist of hexagonal cells, the surface is also 

 faintly punctate. 



Auliscus sculpttis (fig. 197).— Valves of this species 

 are by no means common; but the diligent observer 

 will probably be rewarded with a specimen or two : 

 the valves are frequently slightly oval, with, two 

 circular elevations near the margins, and a smooth 

 centre: the markings consist of lines, some of which 



radiate from the centre, and then suddenly converge 

 towards the marginal elevation. 



Eupodiscus Argus (fig. 19S).— This fine form occurs 

 but sparingly : the surface of the valve is marked 

 with brilliant dots, beneath which appears an irregu- 

 lar arrangement of hexagonal cells of considerable 

 thickness : near the margin will be seen three or 

 more distinct elevations. 



Fig. 198. Eupodiscus Argus, x sno. 



Actmoc!/clusRaJfsii(Rg.l99).— Aspeciessometimes 

 very common : the beautiful blue colour of the valves 

 under a low power renders it a conspicuous object : 

 the markings consist of small pearl-like dots, ar- 

 ranged in radiating series : a minute blank space 

 may be detected near the margin (pseudo-nodule). 



Fig. 199- Actinocyclus Ralfsii. 





Fig. 200. 



Cocconeis 



excentricu, x 400. 



Cocconeis excentnea (fig. 200). — A curious little 

 species, apparently peculiar to sand-gatherings : the 

 valve is nearly circular, with a conspicuous margi- 

 nal band, consisting of small dots, much closer than 

 those on the centre; median line and nodule not 

 central. 



Fig. 201. 

 Tricerutium alternans. 



Fig. 202. 

 Podosira compressa. 



Triceratium alternans (fig. 201). — This is the only 

 species of the genus 1 have detected among the 

 shore forms : valve small, triangular, with rounded 



