420 MR JOHN RATTRAY ON A 



Length, 0-1225 mm.; length of central hyaline area along the longitudinal 

 axis, 00150 mm.; greatest breadth at middle, 00175 mm.; diameter of ter- 

 minal areola, 0*0050 mm. ; costae, 8 in 01 mm. 



14. Navicula cardinalis (Ehrenb.), var. subconstricta, nov. (PI. XXIX. fig. 3). 



Several specimens of small size occur which cannot be assigned to the 

 typical species on account of the following peculiarities: — (1) The apices are 

 separated from the main body of the frustule by the presence of a shallow but 

 distinctly defined constriction (a, a). (2) The terminal hyaline spaces are 

 almost round, and are placed immediately within the margin of the valve. (3) 

 The transverse and obliquely-disposed costae are straight or subarcuate in out- 

 line, but present no undulations along their margins. (4) Several of the costse 

 on the proximal side of the terminal spaces are longer than those adjoining 

 them, and extend close up to the median raphe. (5) The transverse central 

 hyaline space is infundibulate towards both margins, and is slightly broader on 

 one side of the valve than on the other. (6) The costse on one half of the valve 

 are somewhat larger than on the opposite side, so that a slight asymmetry 

 results. The wider side of the transverse central hyaline space is placed on 

 that side of the valve upon which the length of the costse is greatest. 



Length, 0*0825 mm.; greatest breadth, 0*0125 mm.; transverse diameter of 

 terminal space, 0*0028 mm.; width of transverse central hyaline space, 0*0050 

 mm. (narrower side), and 0*0062 mm. (wider side) ; strise, 12 in 0*01 mm. 



15. Namcula inaequistriata, n. sp. (PI. XXIX. fig. 4). 



Valve faintly elliptical, the margins in the median area bulging but very 

 slightly; apices obtusely rounded. Raphe excentric throughout, but passing 

 very near to one side towards its distal end, which is flexed abruptly towards 

 the centre ; its distal flexure is much more pronounced than its proximal, whilst 

 its middle part is slightly arched in the opposite direction. Median hyaline 

 area inequilateral, its outline on the side next the wider half of the valve being 

 much more convex than on the opposite side. Terminal hyaline areas sub- 

 rotund or elliptical, and sharply circumscribed. Striatum well defined, radiating 

 around the central hyaline space, becoming transverse about halfway between 

 the centre and the apices, and again becoming oblique towards the extremities. 

 Striae straight or but very faintly subarcuate. 



Length, 0*0800 mm.; greatest breadth, 0*0100 mm.; greatest transverse 

 diameter of central hyaline space, 00035 mm. ; diameter of terminal areolae, 

 00020 mm.; striae, 10 in 001 mm. 



