20 NAVICULE. 
Navicula pusilla, Smith. 
Navcula pusilla, Sm. Synop. vol. i. p. 52, pl. xvii. fig. 145 ; Ralfs, in 
Prit. Inf. p. 900; Rabenh. Alg. Sub. no. 1185, and Europ. 
Diat. p. 198. ; 
Navicula gastroides, Greg. Quart. Micr. Journ. vol. iii. p. 40, pl. iv. 
fig. 17. 
Plate ITI. figs. 6a & 66. 
Frustule small. V. varying in outline, from suborbicular 
or broadly oval to elliptical-lanceolate, with produced, 
broad, truncate extremities; striz reaching to the 
median line, radiating, granular, stouter, and more 
distant around the centre. 
Had. Fresh and slightly brackish water, frequent. 
Navicula Carassius, Ehrenberg. 
Navicula Carassius, Ehren. Amer. 1843, p. 130, t. I. ii. fig. 12; Kiitz. 
Bac, p. 95, t. xxviii. fig. 67; Rabenh. Siissw. Diat. p. 40, t. vi. 
57, and Europ. Diat. p. 193; Ralfs, in Prit. Inf. p. 900. 
Navicula lacustris, Greg. Quart. Micr. Journ. vol. iv. p. 6, pl. i. 23, 8; 
Ralfs, in Prit. Inf. p. 903; Rabenh. Europ. Diat. p. 200. 
Plate IL. fig. 7. 
Frustule minute. V. elliptical, gradually attenuated into 
produced narrow obtuse extremities; strie reaching 
to the median line, convergent towards the centre, 
distinct, granular. 
A much smaller species than N. pusilla, with much finer 
striz, and at once distinguished by its narrow produced 
apices. 
Hab. Fresh water. River Coquet Northumberland (A. 
S. D.); Loch Leven (Prof. Gregory). 
