72 NAVICULES. 
short elliptical form being the Pinnularia Suecica of Eh- 
renberg. 
Hab. Fresh water. Frequent in hilly and subalpine 
localities in England, Scotland, and Ireland. 
+ Strie parallel, transverse. 
Navicula acrospheria, De Brébisson. 
Frustulia acrospheria, Bréb. Considér. sur les Diatom. p. 19, 1838. 
Navicula Tabellaria, Kiitz. Bac. p. 98, t. xxviii. figs. 79 & 80, t. xxx. 
fig. 20; Ralfs, in Prit. Inf. p. 896, pl. xii. fig. 21. 
Pinnularia Tabellaria, Ehren. ; Rabenh. Siissw. Diat. p.44, t. vi. fig. 24, 
and Europ. Diat. p. 211; var, acrospheria, Rabenh. Europ. 
Diat. p. 21]. 
Pinnularia acrospheria, 8m. Synop. vol. i. p. 58, pl. xix. fig. 183, 
Navicula punctata, Bréb. Journ. of Quekett Micr. Club, Apr. 1870. 
Pinnularia gibba, Rabenh, Siissw. Diat. t. vi. fig. 27 a. 
Pinnularia gibberula, Rabenh. Siissw. Diat. p. 45, t. vi. fig. 30. 
Plate XII. fig. 2, 
Frustule smallish, oblong. V. broadly linear, dilated in 
the middle and at the broadly rounded extremities ; 
strie short, not reaching to the median line, distinct, 
costate, subdistant, parallel and transverse, 26 in‘001"; 
surface of the valve irregularly granular. 
The short transverse strie and the mottled appearance 
of the valve at once distinguish this species from its con- 
geners. In describing it under the name of N. punctaia, 
at the suggestion of the late Prof. Walker Arnott, De 
Brébisson observes (op. cit. supra) :—“ It is this species to 
which I had in 1838 given the name of Frustulia acrosphe- 
ria; but it is not the Navicula acrospheria of Kiitzing, the 
summits of which are not sensibly enlarged—nor, as some 
authors have thought,the Navicula Tabellaria of Ehrenberg, 
which.has no punctuations.” To avoid confusion, I have 
adopted the original specific name of De Brébisson. 
