New Diatoms from Honduras. Described by A. Grunoiv. 179 
Marseilles, by Lindig ; Trieste, by Hauck ; Huitrieres du 
Croisic, Loire inferieure, by Bornet. M. Bornet informs me that 
the oysters become greenish by feeding on this diatom, which 
occurs in great abundance in the oyster-beds at the mouth of the 
Loire. 
This species differs from all other Navicuke hy its fusiform 
outline and resemblance to Amphipleura pellucida. I had formerly 
placed it in Berkeleya, being deceived by the two small dots on 
the median line, which occasionally seem to limit a small linear 
nodule, but more recent investigations with better objectives have 
convinced me that there is only a very small roundish or oblong 
central nodule on each valve. It is the same with my Amphi- 
pleura Frauenfeldii, ‘ Yerh. zool. bot. Gesell.,’ 1. c., tab. i., fig. 19, 
a species closely allied to N. fusiformis, but differing by a some- 
what broader outline, more distinct longitudinal and much coarser 
transverse striae (29 in '01 mm.). The central nodule of this 
species (which must be named Navicula Frauenfeldii ) is exceed- 
ingly small. 
Amphipleura. 
The genera Amphipleura and Berkeleya (inch Bhaphidogloia 
Kg.) are distinguished by the absence of a central nodule, the 
valve is divided by a narrow longitudinal line, terminating at the 
end by long fork-like expansions ; these are very conspicuous in 
Amphipleura, but less so in Berkeleya. The frustules of the 
former are embedded in gelatinous sheaths or in amorphous jelly. 
A. ( pellucida var. ?) Lindheimeri Grun., ‘ Yerh. Wien zool. bot. 
Gesell.,’ 1862, tab. xiii., fig. 11. Yalves lanceolate, • 1 5— * 1 6 mm. 
long, • 024 mm. broad. Transverse striae 26 in -01 mm., longi- 
tudinal striae 26 in -01 mm., slightly curved and interrupted. 
Length of “ forks ” ■ 036 mm. Terminal nodules short, rounded. 
Tab. CXCY., Fig. 13. Texas. 
A. (pellucida var.'l') intermedia Grun. Yalves narrow, lanceolate, 
•19- ‘2 mm. long, • 013- • 015 mm. broad. Length of “forks” 
•044 mm. Striae somewhat finer than in A. Lindheimeri. 
Terminal nodules short, rounded. Oregon deposit ; not very rare. 
A. (pellucida var. ?) Oregonica Grun. Yery large, valves 
lanceolate, • 33 mm. long, • 027 mm. broad. Length of “ forks ” 
• 063 mm. Terminal nodules somewhat elongated, linear. Striation 
like that of A. Lindheimeri. Oregon deposit ; not rare. 
All these forms are closely allied to A. pellucida, and it may 
perhaps he best to consider them all mere varieties of that species. 
The numerous forms of Navicula rhomboides are allied in a similar 
manner, although the extreme members of both series differ very 
widely. I may also add that N. rhomboides is very nearly allied to 
Amphipleura, and that the central nodules are occasionally some- 
vol. xviii. o 
