OF THE FAMILY BACILLAIMA. 159 



LACERNATA. 



Frustulia, Ehr. 

 Envelope double, carapace siliceous, mantle gelatinous, amor- 

 phous, corpuscles scattered or in groups. 



I have seen no American species of this genus.* 



SYNCYCLIA. 



Envelope double, exterior mantle gelatinous, carapace siliceous, 

 navicula-shaped, forming by spontaneous division, circular groups 

 surrounded by gelatine. See Pritchard's Infusoria, PL 4, p. 206, 



No American species has yet been detected. 



NAUNEMA. 



Envelope double, carapace navicula-shaped, siliceous ; mantle 

 gelatinous, exterior, tubidar ; tubes filiform, separate, branching, 

 confervoid, resulting from perfect division of the carapace, and 

 imperfect division of the mantle. 



In this genus, corpuscles which cannot be distinguished from 

 those of Navicuia are assembled together in vast numbers, in 

 flexible membranous tubes, within which they may often be seen 

 to move freely. They doubtless often leave these tubes, and then 

 appear like species of Navicuia. 



I have noticed several American species, but I am unable to 

 decide whether they are identical with any hitherto described, as 

 I have had very little opportunity to study our species in a living 

 state, and have no foreign specimens or figures to compare them 

 with, I shall therefore content myself with merely giving the 

 forms of the frustules found in each species, and such additional 

 particulars as seem most interesting. 



1. Naimenia . (PI. Ill, fig-. 14.) The figure represents cor- 

 puscles from a branching species found on the shores of Staten 



*My opportunity to study the marine Bacillaria, has been very shg-ht. I presume, 

 therefore, that many marine forms not noticed by me during the two days which I spent 

 at Stonington will yet be detected, and among them will probably be species of Frustulia, 

 Syncyclia and Schizonema. 



