New Diatoms from Honduras. Described by A. Grunow. 177 
Orthoneis. 
0. Crucicula Gran. n. sp. 0. minuta, valvis ovatis obtusis, 
loculis utrinque quinque, mediis angustioribus reliquis semicircu- 
laribus, nodulo centrali transversim dilatato cruciformi, striis 
subtiliter punctatis subradiantibus tenuibus (20 in • 01 mm.) 
linea media recta. Longit. *014- *017 mm., latit. valvae '008- 
•01 mm. 
Not rare in the Honduras gathering. 
This is a small but very characteristic species, distinguished by 
the singular shape of its loculi. O. fimbriata (Brightwell) Grun. 
Novara Exped. 
Cocconeis fimbriata Brightwell, in ‘Q. Mic. Jour.,’ vol. vii. fol. 
1, fig. 3. Mastogloia cribrosa Grun., in ‘ Verb. Wien zool. hot. 
Gesellsch.,’ 1860, ex parte tab. vii., fig. 10 d. Common. 
O. binotata Grun., 1. c. page 15. Cocconeis binotata Grun., in 
‘ Yerh. Wien zool. bot. Gesellsch.,’ 1863, tab. iv., fig. 13. C. scu- 
tellum, var. 7 Roper, in ‘ Q. Mic. Jour.,’ vol. vi., pi. iii., fig. 9. 
Common. 
There can be no doubt that these species do not belong to the 
genus Cocconeis, both the valves being alike, and the frustules are 
not concave. It is very doubtful whether these forms are distinct 
from Mastogloia ; the marginal loculi of this genus are represented 
here by small semicircular plates ; these, as well as the loculi in 
Mastogloia, are probably intended for the secretion of the gelatinous 
membrane investing the frustule. This becomes most evident in 
O. binotata, where two long horns (in the living frustule) project 
from it at the places where the two semicircular plates are situated. 
A large number of horns are developed from the frustules of 
O. fimbriata (and O. splendida ?). I have not seen these horns 
on any species of Mastogloia or any other species that I have 
formerly attached to Orthoneis. These species must he placed in 
Mastogloia, and are only distinguished by their ovate valves, a 
difference of little specific value, and of no value as a generic 
distinction. The species are Mastogloia cribrosa (= Cocconeis 
coronata Brightwell ?), M. cocconeiformis, M. ovaia, M. Har- 
vathiana, and several others. [Not having specially studied the 
genus Mastogloia, the following remarks must only be taken for 
what they are worth. This genus was constituted by Thwaites for 
certain naviculoid forms with secondary plates, upon one of which 
are the loculi. The presence or absence of a mucous cushion, 
frond, or stipes, although formerly considered by William Smith and 
others as generic distinctions, are now generally admitted to be 
of no value, even in the determination of species. I have seen 
N. serians and Himantidium Soleirolii embedded in mucous like 
Mastogloia, Cocconema cymbiforme without stipes flourishing 
