138 SKETCH OF THE INFUSORIA 



Our fig. 6, represents a species which is not uncommon in 

 ponds near West Point. The discoid surfaces of the individuals 

 show minute radiating lines quite distinctly. 



5. GaUlonclla sulcata. (PI. II, lig. 7, a, b ?) I noticed frag- 

 ments of this species two years ago in peat from a salt marsh 

 near Stonington, and among marine Alga; in the same vicinity. 

 I had prepared a sketch and description of it lor this memoir, 

 before I heard of the discovery of the infusorial stratum of Vir- 

 ginia. I was, therefore, agreeably surprised to find, on inspect- 

 ing specimens of the fossil infusoria from Richmond, Rappahan- 

 nock Cliff, &c., that this species was very abundant in them. A 

 careful comparison of the recent specimens from Lr'tonington, and 

 tlx" fossil specimens from the tertiary of Virginia, has left no doubt 

 in my mind of their specific identity. The following is the ac- 

 count of the recent specimens, written several months before the 

 reception of the Virginia fossils. They consist of frustules, each 

 of wiiich is divided by a transverse line ; the cylindrical surface 

 of each frustule has a great number of parallel lines in the direc- 

 tion of the axis, and the ends or flat surfaces show a rim having 

 lines corresponding to those on the cylindrical surface ; within 

 this rim is a diaphragm having minute radiating lines. Chains 

 of thirty or forty individuals are not unfrequent in the infusorial 

 earth of Richmond, particularly in the upper part of the stratum. 

 These are doubtless the " oblong cylinders" alluded to by Prof. 

 W. B. Rogers in his Report on the Geological Survey of Vir- 

 ginia, 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. 



" GaiUonella sulcata. Corpuscles cylindrical, short, tnincate at the 

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

 nes en travers et sons forme de cellules,) -^^ to one ^V of a line.* 



* In Pritchard's Iliston' of Infusoria, Recent and Fossil, I find a fijrure of GaiUonella 

 sitlcata,-w\\'\c\\ leaves little doubt that our fossil specimens from Richmond, as well as our 

 recent ones from Stonington, belong to this species. The living animals have also been 

 detected at Cuxhaven. by Ehrenberg. See appendix to Pritchard's work. p. 434. 



