Greville, on New Diatoms. 
127 
This diatom has no immediate affinity with the preceding. 
There is no edging of larger cellules^ but, on the contrary, a 
row of smaller puncta. The general structure, too, is unlike 
what is usually seen in the genus, the puactse, which increase 
in size towards the margin, being not primarily so arranged 
as to produce the effect of strise, but in quincunx fashion. 
Near the margin they are 15 in '001'". 
Navicula Egyptiaca, n. sp., Grev. — Elongated, narrow^ 
convex, with elliptical subacute ends, and very gradually and 
slightly constricted at the middle ; a linear lanceolate band 
of short broad costse midway between the margin and 
median line, interrupted opposite the nodule, and a partial 
view of a second band of costse at the margin. Length 
•0050" to -0065^ (Figs. 16, 17.) 
Hah. Stomachs of Holothurise; in slides kindly com- 
municated by W. J. Baker, Esq., and George Norman, Esq. 
My friend Mr. Ealfs has justly remarked in his observa- 
tions on the genera Navicula and Pinnularia, that, " were the 
costse always plainly developed as in Pinnularia nobiUs and 
its allies, no difficulty could occur in determining the genera ; 
but in many of the more minute species it is often very diffi- 
cult to distinguish between striae and costse and he adds 
very truly, that it is impossible to say to which genus a 
large number of Ehrenberg^s species should be referred. He 
resolves the difficulty by merging for the present, at least, 
Pinnularia in Navicula. The very elegant diatom now 
under consideration would be, according to the late Professor 
Smith, an unquestionable Pinnularia, and it is too well 
marked to be mistaken for any other species. Costse about 
10 in '001". This Holothurian material is rich in many 
species, and there can be no doubt that collections from the 
stomachs of the Holothuriadce generally, especially in the 
warmer parts of the world, would amply reward the diatom 
hunter. 
Navicula permagna (Bail.), Balfs. — Large, lanceolate or 
turgid -lanceolate, with somewhat obtuse apices; striae fine, 
close, an intramarginal line, and a second shadowy line 
between the margin and the median line, and generally 
a rather broad, longitudinal, median blank space. Length 
•0060" to -0108". (Figs. 18—21.) 
Navicula permagna, Balfs, in Pritch. ^Infus.^ (1861), p. 907. 
— Lewis, ^Notes on Diatom, of U. S. Seaboard,^ p. 12, pi. ii, 
fig. 11 (var.). 
Pinnularia permagna, Bail., ^ Mic. Obs.,^ p. 40, pi. ii, 
figs. 28, 38. 
Hab. Abundant in the Hudson River at West Point, and 
