38 GEOEGE WEST ON AMPHORA INFLEXA, 



placed one-third width of valve from ventral margin. From 

 this nodule the very narrow indistinct raphe area is, on each 

 side, arcuate, approaching the dorsal margin to within one- 

 third the width of valve, and extending to the apices which are 

 without nodules. Kaphe exceedingly faint, running along the 

 middle of its narrow area and not entering the central nodule. 

 Striae on ventral side strongly divergent at the middle, slightly 

 convergent towards the ends and parallel between ; on the 

 dorsal side more or less parallel throughout ; at the poles strongly 

 radiate. About the middle of valve the striae number 18-20 

 in 10 /A, towards the ends 22-24 in 10 /x,, finely and delicately 

 punctate (fig, D), Punctae 22-25 in 10 /a, but, owing to the 

 fragile nature of the valve, not so readily seen as they would 

 be if the siliceous shell were thicker. The foregoing features 

 give this species a most distinct appearance when seen in valve 

 view at a magnification of 1,000 diameters. 



Frustule in girdle view almost linear, but tapering slightly 

 towards the abruptly truncate encis (fig. B). Length as above. 

 Breadth of the convex dorsal side li-M /x, at the centre, 7-9 ju, 

 at the ends ; the concave ventral side is slightly narrower (fig. C). 

 The raphe of each valve is distinctly visible on each side of the 

 dorsal aspect, each senii-raphe appearing as a faint line thicker 

 at its middle (fig. B, r). The overlapping girdles are complex 

 in structure. Each is from 5 to 7 yw- wide, and is composed of 

 five or more longitudinal zones of exceedingly delicate silex 

 alternating with zones of thicker silex. These bear longitudinal 

 rows of punctae which run about 30 in 10 /* (fig. E). It will 

 be observed that in size and marldng this species, like many 

 other diatoms, is subject to considerable variation. 



Each frustule contains two elongated chromatophores, each 

 being about 14 jx long, and containing a distinct pyrenoid (fig. 



