92 Sketch of the Infusoria of the family Bacillaria. 



Virginia, p. 39. Ehrenberg gives the following description of 

 Gaillonella sulcata, a fossil species occurring in the schist of 

 Oran ; from this description I suspect it to be closely allied to our 

 species, and therefore copy its specific characters for the purpose 

 of comparison. 



" Gaillonella sulcata. Corpuscles cylindrical, short, truncate at the 

 two ends and flattened, furrowed across and in form of cells" (sillonnes 

 en travers et sous forme de cellules,) gig- to y^. line.* 



6. Gaillonella? . (PL 2, fig. 8.) Corpuscles long, cylindri- 

 cal, with two lines of constriction, adhering by alternate angles so as to 

 form long zigzag chains, and occasionally auricled. 



The curious bodies represented in PL 2, fig. 8, appear to partake 

 of the characters of both Gaillonella and Bacillaria, showing 

 the cylindrical corpuscles of the former, united by alternate an- 

 gles, as in many species of the latter. It is, perhaps, related to 

 Diatoma auritum of Lyngbye, which is described as having the 

 "joints quadrangular, rounded, with an auricle at each angle," 

 and of which Greville remarks that the auricular appendages of 

 the angles give to the frustules the appearance of " microscopic 

 woolpacks." Having seen no figure or specimen of D. auritum, 

 I cannot decide as to its identity with our species ; I believe, how- 

 ever, that ours must be difierent, both from its abundance and 

 from the remark of Kutzing (Linnasa, 1833, p. 585) that D. au- 

 ritum, probably belongs to the Desmidiaceas. 



Our species consists of large cylindrical siliceous joints, usually 

 adhering together by alternate angles in a zigzag manner. Most 

 of the frustules show two lines of constriction, as shown in the 

 figure. The connection of the frustules is by a very conspicuous, 

 flexible hinge-like ligament, which often gives to the joints an au- 

 ricled appearance, which makes the comparison of them to "mi- 

 croscopic woolpacks," or rather bales of cotton, not inappropriate. 



The joints usually contain a yellow or ochraceous substance, 

 arranged in a stellate manner, and not unfrequently this appears 

 to be composed of minute globules, (ova?) as shown in the fig- 

 ure. This species occurs, in vast quantities, in the Hudson River, 

 at West Point. It may be found in some places at low tide, giv- 



* In Pritchard's History of Infusoria, Recent and Fossil, I find a figure of Gaillo- 

 nella sulcata, which leaves no doubt that our fossil specimens from Richmond, as 

 well as our recent ones from Stonington, belong to this species. The living ani- 

 mals have also been detected at Cuxhaven, by Ehrenberg. See appendix to Pritch- 

 ard's work, p. 434. 



