428 MR JOHN RATTRAY ON A 



attached, proximal, then the distal inflation passes much less abruptly into the 

 distal constriction. (2) The outline of this latter forms a much smaller curve, 

 being very similar to that figured by Kutzing in his Die kieselschaligen Bacil- 

 larien oder Diatomeen, pi. xiii. fig. 2a. (3) The margins of the median inflation 

 are also less curved, so that there is in the valve a far easier transition from 

 the apical to the median, and again similarly from the latter to the proximal or 

 basal region. (4) At the side of the central nodule, instead of five elliptico- 

 cuneate unilateral cellules, there are here but two, which are far less prominent, 

 on account of their smaller size, — the area occupied by both, together with the 

 intervening space, being 00025 mm. (5) These cellules are not placed in the 

 middle of the circumnodular hyaline area, but are somewhat nearer its distal 

 than its proximal extremity. (6) This area, formed by the abbreviation of the 

 limiting striae is much larger, and its outline is by no means regular, inasmuch 

 as some of the individual striae pass a good deal further inwards than others. 

 The outlines of the slightly-arched clear spaces surrounding those parts of the 

 median raphe between the central and terminal nodules are, however, quite 

 regular, as figured by W. Smith and Ralfs. (7) The terminal nodules of the 

 raphe are very much less pronounced at the distal and proximal ends of the 

 frustule. (8) The hyaline space at the proximal extremity has an entirely dis- 

 tinct character. It is not bounded by straight moniliform striae, which pass 

 from the distal side of the proximal nodule obliquely outwards to the widest 

 part of the proximal inflation, but the inner ends of the terminal striae, which 

 run obliquely outwards and downwards to a narrower part of this inflation, 

 nearer the base of the frustule, form an almost regular curve, convex on the 

 side next the nodule on both sides of the valve. (9) The striation varies in 

 one important feature. Around the upper lateral margin of the distal inflation 

 the moniliform lines are not straight, but arcuate, the concavity here directed 

 towards the apex of the frustules. This arcuation is continued all round from 

 the straight stria, which runs outwards to the widest part of the distal inflation, 

 to the apex, attaining its maximum of curvature at about two-thirds of this 

 distance from the apex. On the distal constriction and the proximal half of 

 the apical inflation the striae are again slightly, though very distinctly, arcuate, 

 the concavity of the curves being directed basally. (10) To the right of the 

 distal lentelliptical clear space, and towards its lower part, is a hyaline sub- 

 hexagonal areola, extending almost from the median clear space over about 

 two-thirds of this half of the valve. At first sight this seems to be the result 

 of local erosion, but, since it is sharply defined, and as there is no indication 

 of any such action elsewhere, the ornamentation being remarkably clear 

 throughout, there is a strong probability that it is a characteristic of the 

 valve itself. 



