6 NAVICULEX. 
distinguished from it by its much smaller size, oval shape, 
much closer and finer strie, by the straight longitudinal 
line crossing them, and by the colour of the dry valve. 
Hab. Marine. Abundant in several localities on the 
sandy beach of Northumberland. 
Navicula estiva, Donkin. 
Navicula estiva, Donk. Trans. Micr. Soe. n. 8. vol. vi. p. 32, pl. iii. fig. 18; 
Ralfs, in Prit. Inf. p. 899; Rabenh. Europ. Diat. p. 184. 
Plate I. fig. 3. 
Frustule large. V. elongate-elliptical ; strice fine, distinct, 
obscurely granular, subparallel, and crossed near the 
median line by a slightly incurved longitudinal line. 
This species is distinguished from N. Smithi, Bréb., 
with which it is generally associated, by its more graceful 
form and much finer and much less granular strie; dry 
valve blue. 
Hab. Marine. On the sandy ripples of the sea-shore 
(plentiful) at Cresswell, Northumberland; South Shields 
(A. S. D.). Hull (Mr. Norman); New Brighton (Mr. 
Comber). 
Navicula Smithii, De Brébisson. 
Navicula Smithii, Bréb. in Smith’s Synop. vol. ii. p. 92; Ralfs, in Prit. 
Inf. p.898; Rabenh. Europ. Diat. p. 178. 
Navicula elliptica, Smith, Synop. vol. i. p. 48, pl. xvii. fig. 152. 
Navicula didyma, var., Smith, Synop. vol. i. p. 53, pl. xvii. fig. 154%, 
Plate I. fig. 4. 
Frustule large. V. oblong, linear-elliptical, with broadly 
