38 One Thousand Objects 



scurely radiant series of irregular-shaped granules on the 

 valves. Occurs in the mud of estuaries and in dredg- 

 ings. 



270. LITTLE CAMPYLODISCUS (Campylodiscns parvulus). 

 The disc is nearly circular and small, with about twelve 

 ribs. It is usually considerably contorted, and is the 

 smallest species know. Found under similar conditions 

 to the foregoing. (PI. IV., fig. 2.) 



271. ARCHED RHABDONEMA (Rhabdonema arcuatuni). 

 In this genus, the frustules united form a compressed 

 filament with a short stem. The valves are joined to the 

 connecting zone by a series of rings, which are furnished 

 on the circumference with a row of cells. Marine, gene- 

 rally growing on the smaller Algae. (PI. IV., fig. 25.) 



272. MARINE GRAMMATOPHORA (Grammatophora ma- 

 rina}. The frustules in this genus are also united into a 

 filament, which partly separate and form a zigzag chain. 

 Common on small Algae, growing just below low water. 

 (PL IV., fig. 27.) 



273. BEADED MELOSIRA (Melosira nummuloides). The 

 frustules in this genus are usually cylindrical or disc-shaped, 

 cohering in a filament ; but in the present species they are 

 spherical and united in pairs, strung together like a string 

 of beads. Common on Algse. (PI. IV., fig. 26.) 



274. RADIATE COSCINODISCUS (Coscinodiscus radiatits). 

 The valves in the genus Coscinodiscus are circular, and 

 more or less convex. The hexagonal cells in the present 

 species are in radiating lines, and largest in the middle 

 The margin of the valves is smooth. Found in the 

 stomachs of molluscs and in dredgings. (PI. IV., fig. 12.) 



275. EXCENTRIC COSCINODISCUS (Coscinodiscus ecceif 

 tricus). The cells in this species are small, and arranged 

 in excentric lines. The margin of the valve is spinbus. 

 Found also within small molluscs and in dredgings. 



276. DELICATE COSCINODISCUS (Coscinodiscus subtilis). 

 The cellules are small, and arranged in radiating lines 

 from the centre to the circumference. Found in brackish 

 water, frequently attached to the stems of rushes, &c. 



277. RALFS'S ACTINOCYCLUS (Actinocydus Ralfsii}. 



