COSCJNODISCUS. 



[ 171 ] 



COTHURNIA. 



Fig. 143. 



Coryneum disciforme. 



Vertical section of half 



a pustule. 

 Magnified 200 diams. 



in fig. 143 ; the cellular stroma is covered 



by stalked multiseptate 



spores. Five species 



are recorded as British. 



The species figured, C. 



disciforme, Kze., grows 



on dead twigs of birch. 



It is not improbable 

 that this genus is con- 

 nected with some Asco- 

 mycetous form. 



BiBL. Hook. Brit. 

 Fl. V. pt. 2. p. 355; 

 Berk. & Broome, Ann. 

 Nat. Hist. 2 ser. v. 458; 

 Cord a, I cones Fung. 



COSCINODISCUS, Ehr.— A genus of 

 Diatomacese. 



Char. Frustules free, single, disk-shaped; 

 valves circular, flat, or slightly convex, ex- 

 hibiting a cellular or areolar appearance. 

 (No internal septa nor lateral processes.) 



The cellular appearance arises from the 

 existence of depressions, which are of differ- 

 ent sizes. The valves form beautiful objects. 



KUtzing enumerates forty -one species, 

 which are either marine or fossil. Smith 

 admits four British species : 



C. minor, E. Depressions irregular and 

 crowded (circular, Sm.); margin of valves 

 smooth; aquatic and marine ; diam. 1-1200 

 to 1-500". 



C. radiatus, E. (PI. 18. fig. 32). Depres- 

 sions obscurely radiating, marginal ones 

 smallest; margin of valves smooth ; marine 

 and fossil; diam. 1-550 to 1-180" {a, side 

 view; b, front view). 



C. eccentricus, E. Depressions arranged 

 in curved lines, with the convexity towards 

 the centre; marine and fossil; diam. 1-400 

 to 1-200". 



C. craspedodiscus, K. = Craspedodiscus 

 elegans, E. (PL 19. figs. 7 & 8). Margin of 

 valves tumid, elegantly sculptured, central 

 markings (depressions) radiating ; an umbili- 

 cal star formed of 5 to 6 oblong larger ceUs(?) ; 

 diam. 1-120". Bermuda. 



BiBL. Ehr. Ahhandl. d. Berl. Akad. 1838 

 and 1839; id. Ber. d. Berl. Ahad., 1840 et 

 seq. ; KUtzing, Bacillarien, and Sp. Alg.; 

 Smith, Brit. Diat. 1. 



COSMARIUM, Corda.— A genus of Des- 

 midiaceae. 



Char. Cells single, constricted at the 

 middle; segments as broad as or broader 

 than long, neither serrated nor spinous. 



Ralfs admits thhty-three British species. 

 Among the most common are, — 



C. pyramidatum (PI. 10. fig. 18, 19 empty 

 cell). Oval, with depressed and truncate 

 ends, deeply constricted ; end view elliptical ; 

 segments pimctate, entire ; length 1-470 to 

 1-260". 



C. bioculatum. Smooth, depressed, con- 

 striction producing a gaping notch on each 

 side ; end view elliptical ; segments sub- 

 elliptic, entire; sporangium orbicular, spi- 

 nous; length 1-1410". 



C. crenatmn (PI. 10. fig. 20). Punctate, 

 deeply constricted ; segments crenate at the 

 maigin, depressed at the end; end view 

 elliptical ; spines of sporangium very short ; 

 length 1-470'. 



C. tetrophthalmwn (PI. 10. fig. 22). 

 Deeply constricted ; segments semicircular ; 

 end view elliptical ; rough with pearly gra- 

 nules, which give a crenate appearance to 

 the margin; length 1-230''. 



C. margaritiferum (PI. 10. fig. 21). Rough 

 with pearl}' granules, which are as broad as 

 long; end view elliptic; segments semicu*- 

 cular or reniform; length 1-560 to 1-300". 



C. ornatum. Segments twice as long as 

 broad, rough with granules giving a dentate 

 appearance to the margin ; end view with a 

 truncate projection on each side; length 

 1-610". 



C. cucurhita. Punctate, constriction shght, 

 ends rounded; transverse view circular; 

 length 1-580". 



BiBL. Ralfs, Brit. Desmid. pp. 91 & 212. 



COTHURNIA, Ehr.— A genus of Infu- 

 soria, of the family Ophrydina. 



Char. Solitary; carapace urceolate, 

 stalked. 



An anterior ring of cilia is present. The 

 body contracts suddenly, like that of Vorti- 

 cella. 



Dujardin unites this genus with Vagini- 

 cola. 



C. imherbis, E. (PI. 25. fig. 20). Stalk 

 much shorter than the hyaline carapace; 

 body yellowish ; aquatic; length of carapace 

 1-280". Found upon Cyclops quadricornis . 



C. maritima, E. Stalk much shorter than 

 the carapace ; body whitish, hyaline; length 

 of carapace 1-570", On Ceramium. 



C. havniensis, E. Stalk much longer 

 than the carapace ; body whitish ; length of 

 cai'apace \\'ithout the stalk 1-280", stalk 

 twice this length. On Sertularice, &c. 



Stein adds three species, C. Sieboldii, 

 C. astaci, and C. curva ; found upon Astacus 

 fluviatilis (the Cray-fish). 



BiBL. Ehr. Infus. p. 297; Duj. Infus. 

 p. 564 ; Stein, Die Infus. 



