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



Totaree Diatomiste II PL VI f. 5. As Campyoneis notahilin Brun has described a form from Ro- 

 driguez, which, to judge from the figure seems not to differ essentially from C. Grevillei. 



Oocconeis (Ehb.) Cl. 



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

 dinal axial area. Structure: puncta 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 longitudinal 

 axis. Cell-contents (of C. 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 mass, inside which is 

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

 terior of the auxospores contains a lacerate endochrome-plate (Bqrscgw: 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, -prohahlj degenerated forms of 

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

 double rows of smaller puncta, as is also the case with Mastogloia {Orthoneis) splendida. 



All these forms, C. gihhocalyx perhaps excepted, live attached to algaj and other objects 

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

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

 also occurs in brackish water. 



Artificial hey. 

 — straight ... .2. 



^ j Median line sigmoid . C. australis Pet. 



I Axial area of the upper valve lanceolate .... . 3. 



— — — — linear . . 4. 



'{■ 



{ 



Area very hroad. Marine .... . ... C. grata A. S. 



moderately broad. Freshwater habitat C. Disculus Schum. 



. / Upper valve finely striate . . . . . . 5. 



I — — with coarse puncta or alveoli . .... 6. 



,. j Upper valve with a marginal line . . . C. Placentula Ehb. 



"^ ' \ — — without ... . C. Pediculus Ehb. 



„ j Upper valve coarsely reticulate . . . . C. Van HewcMi Cl. 



■ \ — — — punctate 7. 



j Margin of the upper valve finely striate ... 8. 



\ — — — — not — . . . . . . 9. 



f Rows of puncta in the upper valve 4 to 5 in 0,oi mm. C. granulifera Grun. 



Q 



■ ^ — 8 to 9 — — C. cruciata Pant. 



- ( Valve lanceolate . . . . . C. gibbocalyx Brun. 



I — elliptical ... . 10. 



Puncta of the upper valve forming equidistant transverse and (usually) 



10. { straight longitudinal rows C. Scutellum Ehb. 



— not — — — — C. distans Greg. 



1. C. granulifera (Jrbv. (1861). — Outline elliptical, with broad, rounded ends. L. 0,02 8 

 to 0,05 7; B. 0,018 to 0,038 mm. Upper V. with finely striate margin (striae 17 in 0,oi mm.), 

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

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

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



