Mr. C. Mereschkowsky on Stauronella. 433 
in the type, but usually broadly rounded, never cuneate and 
so acute as in fig. 35, pl. xxvi., of A. Schmidt’s ‘ Atlas.’ 
The main distinction, however, between var. linearis and the 
type as regards their valves consists in the absence of any 
constriction in the middle of the valve. 
The girdle-face presents a still greater number of distinctive 
features. It is broader, more quadrangular, the lateral 
margins are not so convex and the median constriction so 
marked; the extremities are more truncate. The longitu- 
dinal divisions of the zone terminate with a punctum, of 
which the four outer puncta, situated inside the terminal 
nodules, are very conspicuous. This latter characteristic, 
insignificant as it may appear, is nevertheless very constant 
and readily distinguishes var. linearis from the type species, 
which never has the above-mentioned four puncta. ‘he 
size is also a little smaller, averaging 0:037 mm., instead of 
0:0413 mm. 
The following are some individual measurements : — 
Breadth of At the 
Length. the frustule. constriction. 
mm. mm. mm. 
0-015 0:0095 0-009 
0-016 0:0095 Mae: 
0-02 0:0076 
0-02 0:0086 
0-024 0-0086 Ape 
0-031 0:0105 0-0086 
0-040 0-018 0-0105 
0-041 O-0114 0:0095 
0-041 0-012 0:0095 
0-041 0-017 0:0148 
0:0427 0:0105 es 
00427 0:0105 0:0076 
0:050 0:0105 0:0076 
0-050 0-012 0:0095 
0:052 00114 0.0086 
0:055 0:0114 0 0095 
0-053 0-012 0:0095 
Average .. 0-037 0:0109 00095 
If we compare the measures of the type species with those 
given by Cleve (length 0°05-0°140 mm.) we can clearly see 
that the form described by this author is not the same as that 
which has been figured by Peragallo and described by me. 
In all probability it represents a peculiar large variety, 
which ought to be distinguished as var. major. Peragallo, 
Ann. & Mag. N. Hist. Ser. 7. Vol. viii. 31 
