NAVICULA HITCHCOCKII. 29 
Navicula dirhynchus, Ehrenberg. 
Navicula dirhynchus, Ehren. Amer. p. 181, t. III. i. fig. 11; Kiitz. Bac. 
p. 95, t. xxviii. fig. 48; Rabenh. Siissw. Diat. p. 40, t. vi. 
fig. 48; Ralfs, in Prit. Inf. p. 901. 
Naviewa rhynchocephala, Kiitz., var. parva, Rabenh. Europ. Diat. p.196. 
Plate V. fig. 3. 
Frustule small. V. hyaline, nearly linear, with a slight 
constriction beneath the obtuse extremities; striz 
inconspicuous ; median line dark and conspicuous ; 
terminal nodules not reaching to the apices. 
In outline this species has a strong resemblance to N. 
affinis ; but it is much smaller, and distinguished by the 
apparent absence of striz. 
Hab. Fresh water. R. Coquet Northumberland : fre- 
quent (4. S. D.). 
Navicula Hitchcockii, Ehrenberg. 
Navicula Hitchcockit, Ehren. Amer. p. 180; Mikrogeo. t. V. iii. fig. 11; 
Kiitz. Bac. p. 101; Ralfs, in Prit. Inf. p. 894,-pl. vii. fig. 62. 
Plate V. fig. 4. 
V. oblong, linear, margins triundulate, extremities cuneate, 
slightly incurved, acute; striz fine, transverse, reach- 
ing to the median line and central nodule. 
Hab. Fresh water. Loch-Oich deposit, Caledonian 
Canal (4. 8. D.). I can find no notice of this species 
having been previously discovered in Europe. 
