COSCINODISCUS. 



[ 171 ] 



COTHURNIA. 



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 Fl g- l43 - 



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. \.458-, 

 Corda, Icones Fung. 



COSCINODISCUS, Ehr. A genus of 

 Diatom aceae. 



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. 



Kiitzing 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 to6 oblong larger cells(?) ; 

 diam. 1-120". Bermuda. 



BIBL. Ehr. Abhandl. d. Berl. ATcad. 1838 

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

 seq.; Kiitzing, Bacillarien, and Sp. Alg.-, 

 Smith, Brit. Diat. 1. 



COSMARIUM, Corda. A genus of Des- 

 midiacese. 



Char. Cells single, constricted at the 

 middle; segments as broad as or broader 

 than long, neither serrated nor spinous. 



Ralfs admits thirty-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 punctate, 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. crenatum (PI. 10. fig. 20). Punctate, 

 deeply constricted ; segments crenate at the 

 margin, depressed at the end; end view 

 elliptical ; spines of sporangium very short ; 

 length 1-470". 



C. tetrophthalmum (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 pearly granules, which are as broad as 

 long; end view elliptic; segments semicir- 

 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. cucurbita. Punctate, constriction slight, 

 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. imberbis, 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 

 carapace without the stalk 1-280", stalk 

 twice this length. On Sertularite, &c. 



Stein adds three species, C. Sieboldii, 

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

 flumatilis (the Cray-fish). 



BIBL. Ehr. Infus. p. 297; Duj. Infus. 

 p. 564 ; Stein, Die Infus. 



