168 P. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Totarce Diatomiste II Pl. VI f. 5. As Campyoneis notabilia Brun has described a form from Ro- 

 driguez, whicli, to judge from the figure seems not to diifer essentially from C. Grevillei. 



Cocconeis (Ehb.) Cl. 



Valve in outline broadly elHptical. Upper valve ecostate, with a more or less narrow longitu- 

 dinal axial area. Structure: punota or alveoli arranged in transverse and, frequently, longitu- 

 dinal rows. Lower valve usually with a marginal line or marginal area. Between the valves is 

 a more or less rudimentary, loculiferous annulus. Frustules usually bent along the longitiidinal 

 axis. Cell-contents (of G. Pediculus) a single chromatophore-plate, along the inside of the upper 

 valve, lacerate at the margin and with a deep sinus from the margin to the centre, where the 

 nucleus is embedded in the central plasma-mass (Pfitzer, Bau u. Entw. p. 87). In conjugation 

 two cells split at the lower valve and secrete a voluminous gelatinous mäss, inside which is 

 formed a large globular auxospore, the exosporium of which is hyaline and without ribs. The in- 

 teriör of the auxospores contains a lacerate endochrome-plate (Bqrscow: Sussw. Bac. p. 97). 



This genus comprises the most common species of the old genus Cocconeis. The obsoletely 

 loculiferous rim indicates that these species are akin to Mastogloia, probably degen erated forms of 

 that genus. In several forms of C. Scutellum the rows of puncta end near the margin in short 

 double rows of smaller puncta, as is also the case with Mastogloia [Orthoneis) S2)h;ndida. 



All these forms, C. (jihhocolyx perhaps excepted, live attached to algai and other objects 

 in the water by the lower valve. C. Placenfula, C. Pediculus and C. Disculus live in fresh, but 

 also, especially C. Pedic, in brackish water. The other species are marine, but O. Scutellum 

 also occurs in brackish water. 



^■{ 



Artificial hey. 



Median line sigmoid G. australis Pet. 



■ — — straight 2. 



I Axial area of the upper valve lanceolate 3. 



\ — — — — — linear 4. 



I Area very broad. Marine • . . . C. gråta A. S. 



\ — moderately broad. Freshwater habitat C. Disculus Schum. 



f Upper valve finely striate 5. 



1 — — with coarse puncta or alveoli 6. 



I Upper valve with a marginal line C. Place.ntula Ehb. 



\ — — without C. Pediculus Ehb. 



J Upper valve coarsely reticnlate C. Van Seurckii Cl. 



\ — — — punctate 7. 



I Margin of the upper valve finely striate 8. 



\ — — — — not — 9. 



f Rows of puncta in the upper valve 4 to T) in 0,oi mm C. granuUfera Grun. 



■ 1 — — — — — 8 to 9 — — C. cruciata Pant. 



( Valve lanceolate C. gibbocalyx Brun. 



" ' ' — elliptical 10. 



Puncta of the upper valve forming eqnidistant transverse and (usuallj') 

 . straight longitudinal rows C. Scutellum Ehb. 

 ( — — — not — — — — C. distans Geeo. 



,„.( 



1. C. graniilifera G-rev. (1H61). — Outline elliptical, with broad, roxmded ends. L. 0,02 8 

 to 0,u.')7; B. 0,ois to 0,038 mm. Upper V. with finely striate margin (striaj 17 in 0,oi mm.), 

 narrow axial area and radiate rows (4 to 5 in 0,o) mm.) of large puncta (about 5 in each row). 

 Lower V. with finely striate margin (stria; 20 in 0,oi mm.). Axial area indistinct; central area 

 small rounded. Median line straight, reaching to the margin. Striic about 13 in 0,oi mm. strongly 



