242 Transactions of the Boyal Microseojpieal Society. 
demi-stauros. Frustule constricted at the centre, ends truncate, 
connecting zone smooth. Length 55 to 74 yu, breadth 17 ya 6. 
Foveaux Strait. PI. XIV., Fig. 15. 
This is a remarkable form ; in the s. v. it appears to be allied to 
N. Bichardsonianaf from which it differs by the terminal nodules 
being placed a little below the apices, and by the blank space on 
one side of the central nodule. [In this respect resembling Pfitzer’s 
genus Anomaeoneis. — F. K.] 
12. N. rhomhus (P. Petit). Valves conspicuously rhomboid, 
apices acuminate and slightly produced, median line straight, 
nodules very small, striae decussating and very close. Length 
36 yLt 6, breadth 24 //, 2 ; about 35 striae in 25 //,. 
Foveaux Strait. PI. XIV., Fig. 12. 
This little species is remarkable for its rhomboid form and 
crossed striae, which under a high power form lozenges arranged in 
quincunxes. It is very closely allied to the species described and 
figured by Lewis t as N. placentula, Ehr. [This is not N. 
placentula, but ~N. rostellum, W. S., ‘ Sy. Brit. Diat.,’ vol. ii. p. 93 
= N. a'piculata, Grreg., ‘Quart. Jour. Mic. Sci.,’ vol. iv. p. 4, pi. i. 
fig. 13. I have seen authentic specimens of this form ; it is not 
uncommon in fresh-water gatherings from Morven, Aberdeenshire, 
communicated by my friend, the Eev. G. Davidson of Logie 
Coldstone. — F. K.] 
Stauroneis, Ehr. 
13. S.rohusta (P.Vetit). Valves elliptical, suddenly acuminate 
towards the ends ; median line straight ; central nodule large, 
terminal nodules small and placed a little below the apices ; stauros 
dilated towards the margin, but which it does not reach ; striae 
interrupted by marginal blank spaces ; margin annular, striated ; 
frustule strongly contracted at the centre, and largely rounded at 
the summits ; connecting zone smooth. Length 90 to 101 ya, 
breadth 28 ya. Striae, 18 in 25 /x. 
Foveaux Strait. PI. XV., Fig. 16. 
This sj^ecies is distinguished from all others by its suddenly 
acuminated aj^ices, the position of the terminal nodules, its annular 
margin, the interruption of the striae, the contraction of the 
frustules at the centre, and their rounded apices. 
[This form undoubtedly belongs to the group of which Navi- 
cula aspera {S. pulcliella, W. S.) is the type. The forms have 
no true stauros, but only a median blank space, which is some- 
times dilated, and sometimes circular. — F. K.] 
Amphiprora, Ehr. 
14. A. rugosa (P. Petit). Valves in f. v. narrow, contracted at 
the centre ; apices terminating in curved points ; striae represented by 
* O’Meara, ‘ Irish Diat.,’ p. 339, pi. 32, fig. xxxiii. 
t ‘U. S. Diatoms,’ part iii. p. 8, pi. ii. fig. 7. 
