100 Sketch of the Infusoria of the family Bacillaria. 



EUNOTIA. 



Free, single or binary, carapace simple, bivalve or multivalve 

 [siliceous) prismatic, four openings on the same side, iivo at each 

 end, ventral side flattened, back convex and often dentate, never 

 catenate by perfect spontaneous division. 



1. Eunoiia arcus. (PI. 2, fig. 26, a, b.) Striate, carapace semi- 

 lanceolate, elongated, two terminal knobs arcuate, 11 striae in y^tt ^^^g. 



Ehrenbeig mentions £1. arcus as occurring among fossil infu- 

 soria from West Point. I presume that our figure, which rep- 

 resents a form very common both in the recent and fossil state in 

 the United States, belongs to this species. 



3. Eunotia diodon. (PI. 2, fig. 29.) Striate, carapace elongated, 

 ventral side flattened, slightly bidentate at the middle of the back, 19 

 strife in y^^ line, ^V to ^\ line. 



Hab. West Point, fide Ehrenberg. Probably the same as fig. 

 29, which is common both recent and fossil at West Point, and 

 elsewhere in the United States. 



3. Eunotia tetraodon. (PI. 2, fig. 31.) Striate, carapace semi- 

 lunar, short, flattened or concave on the ventral side, four rounded teeth 

 on the convex back, 23 striaB in y^^ line, -^-^ to -^-^ line. 



Common among fossil infusoria from Manchester, Mass., and 

 West Point, N. Y. The living species occurs at West Point. 



4. Eunotia pentodon. (PI. 2, fig. 32.) Striate, carapace semi-lu- 

 nar, short, five teeth on the convex back, 23 strise in y^y line. 



Fossil at Manchester, Mass. Living at West Point. 



5. Eunotia serr a. (PL 2, fig. 33.) Striate, carapace linear, slightly 

 curved, twelve to thirteen rounded teeth on the convex back, 19 strice 

 in y^i7 line, -g-^g- to J^ of a line. 



Our figure is from specimens found fossil in Massachusetts. I 

 have also received it from various other localities. 



I strongly suspect that the number of the teeth on the back of 

 the fom' last described species of Eunotia, is liable to variation, 

 and that the number of species has in consequence been made too 

 great. See remarks in Final Report on Geology of Massachu- 

 setts, Vol. II, p. 310, et seq. 



6. Eunotia . (PI. 2, fig. 27, a, b.) This species was found 



in water from a brackish ditch in New Jersey, which was sent to me 

 for examination by Dr. Torrey. It is concave on one side, convex on 

 the other, with a slightly elevated and widened portion in the middle. 

 It is also minutely striate. 



