OF THE NAVICULE^. 



917 



Sinensis, EB. 1847, p. 484 ; EM. pi. 34. 7. 

 f. 11. China. 1-80". 



P. r ever sum (Greg.). — Elongated 

 narrow-linear, with inflated or lanceolate 

 centre, and dilated ends which are turned 

 in contrary directions ; median line sig- 

 moid, subcentral except near the ends ; 

 striae extremely fine. GDC. p. 58, pi. 6. 

 f. 105. Marine. Scotland. This form 

 may be identical with P. Sinensis', but 

 the valves are narrower and with less- 

 rounded apices than in Ehrenberg's 

 figure of that species. 



3 * Valves linear. ■ 



P. Balticum (E., S.). — Large, broadly 

 linear, straight, except towards the 

 attenuated obtuse ends, which are curved 

 in contrary directions ; longitudinal and 

 transverse striae, 38 in -001" ; colour 

 dark brown. SD. i. p. 66, pi. 22, f. 207. 

 -Navicula Baltica, E Inf. pi. 13. f. 10; 

 Gyrosigma Balticum, Rab I), p. 47, pi. 5. 

 f. 6; P. makron, Johnston, MJ. \\\\. 

 Marine or brackish waters. Common, 

 (vm. 33; ix. 144.) 1-70". Median 

 line flexuose, subcentral 



P. ohsctirum (S.). — Small, linear, with 

 attenuated, rather obtuse ends ; median 

 line very flexuose, not central ; striae ob- 

 lique, 75 in -001". SD. i. p. 65, pi. 20. 

 f. 206. Marine or brackish waters. Britain. 

 Var. /3 smaller. 1-193" ; colom- pale pink ; 

 median line marginal near the ends. 



P. simum (E.). — Small, linear, with 

 the ends obliquely rounded on opposite 

 sides ; median line sigmoid, nearly cen- 

 tral. = Navicula sima, EB. 1845, p. 363 ; 

 EM. pi. 34. 7. f. 9. India. 1-430". 



P. Scalpellum (K.). — Small, linear, 

 slightly sig-moid, gradually attenuated 

 into the obtuse apices ; median line svih- 

 central. = Navicula Scalpelhwi, KA. p. 85; 

 KB. pi. 30. f. 13 ; Gyrosigma Scalpellum^ 

 Rah p. p. 47, pi. 5. f. 10. Trinidad, 

 Persia. 



P. Sciotoensis (Sullivant). — Linear, 

 moderately sigmoid, gTadually attenu- 

 ated into the rather obtuse ends ; striae 

 transverse and longitudinal, 40 in '001". 

 SiUiman's J. xxvii. p. 251. Fresh water. 

 United States. -001". "NotimlikeP. 

 Spencerii, for which it has passed as a 

 variety ; but it is a larger species, with 

 sides more parallel and ends less acute. 

 Its striation at once distinguishes it " 

 (SuU.). 



4 * Valves lanceolate or linear-lanceolate. 

 t Valves linear-lanceolate. 

 P. Wansheckii (Donkin). — Linear-lMte 



ceolate, \\dth tapering, subacute, slightly 

 sigmoid ends ; median lines sigmoid, 

 not central ; longitudinal and transverse 

 striae, about 50 in 001". Donkin, TM. 

 vi. p. 24, pi. 3. f. 7.= P. Balticurn, /3, SD. 

 Marine. England. Pale straw-coloured. 

 •0045" to -005". Much smaller than P. 

 Balticum, and with more numerous striae. 



P. lamprocaynpum (E.). — Slender, 

 narrowly linear-lanceolate, tapering to 

 the rather obtuse apices ; sigmoid, with 

 fine transverse striae ; median line cen- 

 tral; front view Y\Vi&2x.— Navicula lam- 

 procampa, EB. 1840, p. 20 ; KB. p. 102, 

 pl. 4. f. 5 ; Gyi-osigma lamprocampum, 

 Kab D. p. 47, pl. 5. f. 9. Marine. Europe, 

 1-144". 



P. curvulum (E.). — Linear-lanceolate, 

 with rather obtuse apices, sigmoid. = 

 Navicula ciirvula, E Inf pl. 13. f. 14 ; 

 Gyrosigma curvulum, Rab D. p. 47, pl. 5. 

 f. 8. Em-ope, America. 



P. speciosum (S.). — Linear-lanceolate, 

 flexed chiefly at the somewhat abrupt, 

 obtuse ends ; median line submarginal 

 near the ends ; striae oblique, 44 in -001" ; 

 SD. i. p. 63, pl. 20. f. 197. England. 

 Pale straw-colour. 1-85". It is shorter, 

 less tapering, and has more rounded 

 apices than P. formosnm; the median 

 line also is not diagonal at the centre. 

 ^ V.formosum (S.). — Large, elongated, 

 linear-lanceolate, much flexed, gradually 

 tapering to the obtuse apices ; median 

 line diagonal ; striae oblique, 36 in -001". 

 SD. i. p. 63, pl. 20. f. 195. Marine. Eng- 

 land. (^Tdi. 32.) Colour chestnut-brown. 

 1-66". Well distinguished by the po- 

 sition of its median line, which, owing 

 to a twist in the valves, appears to coin- 

 cide with the edges for a considerable 

 distance at either end, and then crosses 

 in a diagonal direction. 



P. Longinum (Bri.). — Lanceolate, 

 flexm'e moderate, extremities greatly 

 elongated, acute ; median line central ; 

 striae transverse, 36 in -001". -020" to 

 •025". Colour pale straw. TM. vii. 

 p. 180, pl. 9. f. 7. Arctic regions. 



P sinuosum (E.). — Small, striated, 

 linear-lanceolate; striae 15 in 1-1200". 

 1-480". = Navicula sinuosa, EB. 1840, 

 p. 21. Marine. Europe. Has the figm*e 

 of P. simum, but is more slender. 



P. subtile (Breb.). — Very slender, pel- 

 lucid and delicate ; slightly sigmoid, very 

 narrow linear-lanceolate, subuliform with 

 rather obtuse apices. = Navicula subtilis^ 

 KA. p. 87. Marine. France. 1-160" 

 to 1-120". 



P. tenuissimum (S.). — Very narrow 

 linear-lanceolate, gradually tapering to a 



