352 



DENTICULA. 



D. tenuis Klitz. (Baa, pi. 18, f. 8; H.V.H. Atl., pi. 49, f. 28 to 



31* ; Type No. 332), plate 11, fig. 461. 



Valves longly lanceolate, with apices more or less produced-rostrate, carina 

 conspicuous, costse 7 or 8 in 1 c.d.m. ; striae fine, 17 in 1 c.d.m. Girdle face 

 broad, showing the carina in the form of a median inflation. Length, 1*5 to 



4 - 5 c.d.m. 



Fresh water. England (Norman, Johnson, W. Sm.). Scotland (Dickie, Arnott). France, 

 Belgium (Ard. Lieg. De Wild. 



var. infiata. (D. inflata W. Sm) ; H.V.H. Atl., pi. 49, f. 32 to 34*; 

 Type No. m\ plate 11, fig. 462. 



Valve broadly lanceolate, very slightly attenuated up to the apices. 

 About 3 costa? in 1 c.d.m. 



Fresh water. Brussels (Delogne), England (Norman. W. Sm.), France. 



var. frigida. (D<Jrigida Kidz. ; H.V.H. Atl., pi. 49, f. 35 to 38*; 

 Type No. 334), plate 11, fig. 463. 



Valve sublinear or moderately lanceolate, with attenuated apices. 

 Costa? 5 or 6 in 1 c.d.m. 



Not yet found in Belgium. England. 



D. subtilis Grim. (Oest. Diat., p. 546, pi. 12, f. 36; H.V.H. 

 Atl., pi. 49, f. 10 to 13*), plate 11, fig. 464. 



Valve narrowly lanceolate, with acute apices, carina invisible ; stria? very 

 fine, about 30 in 1 c.d.m. ; costae 6 or 7 in 1 c.d.m. Girdle face very narrow. 

 Length, 1*5 to 2 c.d.m. 



Brackish water. Not yet found in Belgium. England (Newhaven, Grunow). 



Tkibe XV. Tabellarie/E. 



/. False septa well developed. 



Only two [ Se P ta straight, with three openings 



false 

 septa. 



More than 

 two false - 

 septa. 



Septa undulated or hamulous, with only a single median 

 opening ...... 



r 



Fossil 

 or fresh 



water 

 diatoms. 



Valves 



furnished 



with 



costae 



f Valves orbicular 



Valves elliptic, linear, cruciform 

 or inflated 



I 



Valves without eostre, linear, inflated at the 

 median portion and at the apices 



Marine 

 or fossil 

 diatoms. 



Valves 



furnished 



with 



costae 

 or robust 



beads. 



C Septa having one to three round 

 openings . 



j 



1 Septa having numerous open- 

 ings delimited by scalarilorm 



I partitions . 



I 



Frustules very delicate, valves without costae, 

 beads delicate 



II- Rudimentary false septa reduced to knobs 



Diatomella. 



Grammatophora. 

 Stylobiblium. 



Tetracyclus. 



Tabellaria. 



Rhabdonema. 



Climacosira. 



Striatella. 

 Lamella. 



