32 One Thousand Objects 



223. RIBBED CAMPYLODISCUS (Campylo discus costatus). 

 The frustules are saddle-shaped and contorted; the 

 valves circular, with radiating channels ; the centre 

 minutely dotted. Frequently associated with the species 

 Above described. 



224. LITTLE CYCLOTELLA (Cydotella minutula). The 

 frustules are either free or united, and of a flattened, circu- 

 lar, or discoid shape. The valves with radiating stria?. 

 In this species the valves are not undulate. Common 

 in fresh water. 



225. KUTZING'S CYCLOTELLA (Cydotella Kiitzingiana). 

 The valves are undulated, and the delicate radiating 

 strias form a broad marginal band ; centre of disc smooth. 

 Common in fresh and brackisliAvater. (PI. IV., figs. 1 1, 1 1 a.) 



226. COMMON ORTHOSIRA (Orthosira orichalcca). In 

 this genus a cylindrical filament is formed by the union of 

 numerous frustules, usually spiny or toothed at the line of 

 junction. The filaments in this species are straight, and 

 the face of the junction surfaces smooth. Common every- 

 where. (PI. III., fig. 37.) 



227. SAND ORTHOSIRA (Orthosira arenaria}. Filament 

 curved, very rigid; valves with a line of dots; junction 

 surfaces with radiating stride. Not so common as the 

 preceding. (PI. IV., fig. 3.) 



228. VARIABLE MELOSIRA (Melosira variant). The 

 frustules are cylindrical, attached end to end in a filament. 

 The valves are cylindrical, with flattened or truncated ends. 

 Found in every clear spring or river, from the lowest to 

 the most elevated situations. When living, of a rich golden 

 yellow or chestnut hue. 



229. PARASITE COCCONEIS (Cocconcis pediculus). In 

 this genus the valves are elliptical, with a line down the 

 middle and a nodule in the centre. In the present species 

 the frustule is arched, the valves elliptical, somewhat angu- 

 lar, and delicately striated. Parasitic on small water-plan cs 

 and confervas. 



230. FLAT COCCONEIS (Cocconds placentidd). The 

 frustules are flat, and the elliptical valves striated. Of 

 frequent occurrence with the above, (PI. IV., fig. 35.) 



