216 DESCRIPTION OF [Poli/ffiistrica. 



same locality as the preceding, and only differs from it in 

 the markings of its lorica, which are very delicate concen- 

 tric undulatino; lines. Length l-432nd. 



274. CoccoNEis placentula. The cake Coccone'is has a 

 smooth elliptical flat lorica, with an abrupt margin. Found 

 upon vaucheria and lemna. Length 1- 1440th. 



275. CoccoNEis pediculus. The parasitical Coccone'is 

 infests the Navicula*; it has an oval, convex, and smooth 

 lorica. Length 1 -2200th. 



27G. CoccoNEis (?) finnica has an oval lorica, slightly 

 convex, and smooth externally ; internally it is striated. 

 Found fossil in Finland. Length 1 -570th. 



277 -CoccoNEis (?) clypeus. The round Cocconeis is 

 slightly curved, externally it is smooth, but striated within. 

 Found fossil, in siliceous paste (Kiesselguhr) in Franzensbad 

 and Bohemia. Original drawings of this elegant fossil 

 Infusoria are shewn in plate xii., fig. 516 to 518. It has 

 recently been placed in a new genus, under the name 

 Campilodiscus. Diameter of disc l-430th to l-240th. 



Genus LXI. Bacillaria. The zig-zag or true stick 

 Animalcules are unattached to a pedicle, have a simple 

 bivalved or multivalved siliceous lorica, in the form of 

 a many-sided prism. In consequence of the perfect self- 

 division of the lorica, but incomplete separation of the 

 body, they form gaping or zig-zag chains, as shewn in 

 fig. 166 to 17O; even when thus connected together they 

 are motile. " The organs of locomotion," says Ehrenberg, 

 " are soft peg-like processes, projecting from a longitudinal 

 cleft. In B. tabellaris, transparent polygastric vesicles 

 have been seen. Two openings are visible at the end 

 of the lorica : hitherto the nutritive ors^ans have not l)een 



