OF THE FRAGILARIE-E. 



781 



resembles a Trvblionella about as miicli 

 as it does a Nilzscliia, Greg. 



3 * Front vieiv sigmoid (Sigmatella, 

 Kii'tz.). 



N. sigmoidea (Xitzscli, S.). — Front 

 A-iew elongated, broadly linear, sigmoid 

 with truncate ends and marginal pimcta ; 

 valves narrow linear-lanceolate, ^^tli 

 tapering ends and a single longitudinal 

 seiies ofpuncta ; strife 85 in -001". SBD. 

 i. p. 38, pi. 13. f. 10-^. = Kavicula sig- 

 moidea, EI. t. 13. f. 15; Syncdra sig- 

 moidea, KB. p. 67 ; Sigmatella JVitzschia, 

 KSA. p. 18 ; Nitzscliia elongata, Hassall, 

 B Alg. p. 435. Fresh water. Europe. 

 (rx. 148.) Large, with elegantly punc- 

 tate margins. The strife in this Diatom 

 are sometimes strong and easily seen, 

 while others in the same slide set at 

 defiance every method of illumination to 

 bring them out. Mr. SoUitt, of Hull, 

 says, " The striae vary from 65 in the 

 •001" up to a degree of fineness which 

 no lenses that we now have will show." 



N. Brehissonii (Klitz., S.). — Front view 

 broadly linear, sigmoid with truncate 

 ends and marginal puncta ; valves linear, 

 with attenuated, obtuse apices ; striie 27 

 in -001". SBD. i. p. 38, pi. 31. f. 266. 

 = Synedra Armoricami, KB. t. 4. f. 34 ; 

 Sigmatella Brehissonii, KSA. p. 18, 

 France, England. Resembles N. sig- 

 moidea, but is much broader in propor- 

 tion to its length, the puncta are more 

 conspicuous, and the lateral view is more 

 linear. According to Professor Arnott, 

 this species is not the Sigmatella Bre- 

 hissonii of Kiitzing, the latter beino- a 

 mere variety of N. sigmoidea, whilst 

 Smith's species is distinct and a brackish- 

 water species. 



N. macilenta (Greg.). — Front view 

 elongated, linear, siginoid, trimcate ; 

 valves linear lanceolate, with acute api- 

 ces ; keel with a single row of subremote 

 puncta ; strife verv obscm*e. Grev MJ. 

 vii. p. 83, pi. 6. f. 8, 9. Marine. Scot- 

 land. Allied to N. sigmoidea, but de- 

 cidedly less sigmoid. The side view 

 very narrow ; puncta separated from each 

 other by iiTegular intervals, and fewer 

 (8 in 'OOl") than in N. sigmoidea, Gre- 

 ville. 



N. Sigma (K., S.). — Front view sig- 

 moid, linear lanceolate, gTadually taper- 

 ing to the truncated apices; keel of valves 

 ^^■ith a double row of puncta. SBD. i. 

 p. 39, pi. 13. f. 108. = Synedra Sigma, KB. 

 p. 67, t. 30. f. 14. Marine. Em^ope. 

 Strire 56 in -001", S. (iv. 20.) 



N. Sigmatella (Greg.). — Front viewsig- 



moid, linear lanceolate, gradually taper- 

 ing to the obtuse apices ; valves linear, 

 acute, with obscure strife. Greg MJ. iii. 

 p. 4, f. 2. = N. curvida, SBD. ii. p. 39. 

 Fresh water. Europe. Distinguished 

 from N. Sigma by its far more delicate 

 sti'ife and freshwater habitat. Professor 

 Kiitzing describes the Navicula curvula 

 as straight in the front and sigmoid in 

 the lateral view ; it is therefore probably 

 a Plem^osigma, and not this species, as 

 supposed by Smith. 



N. vermicularis (K.). — Front view sig- 

 moid, slender, linear or slightly dilated 

 at the middle ; striae 6h&Qm:e.= Synedra 

 vermicularis, KB. t. 4, f. 35 ; Sigmatella 

 vermicularis, KSA. p. 18. Fresh water. 

 Em'ope. 



N. Tergestina (K). — Front ^lew sig- 

 moid, linear, truncate ; valves naiTow 

 linear, ^\dth suddenly contracted, pro- 

 duced apices. = Synedra Tergestina, KB. 

 p. 66, t. 4. f. 33; Sigmatella Tergestina, 

 Rab D. p. 56. Europe. 11 striae in 

 1-1200", Bab. 



N. Italica (Eab.). — Front view broad- 

 ly linefir, slightly sigmoid, truncate ; 

 valves sigmoid, with attenuated rounded 

 ends, and 9 striae in 1-1200". = Si fpnatella 

 Italica, Eab D. p. 56, t. 4. f. 12. Italy. 



N. ohtifsa (S.). — Front view sigmoid, 

 linear, with rounded apices ; valves linear, 

 obtuse, ^\dth a double series of puncta ; 

 striae 56 in -001". SBD. i. p. 39, pi. 13. 

 f. 109. Brackish water. Sussex. 

 _ N. Smithii. — Front view broadly 

 linear, sigmoid, tnmcate, with conspf- 

 cuous marginal capitate striae havmg 

 smaller pimcta interposed between them ; 

 valves distinctlv striate. =:i\7tec/»a spec- 

 tahilis, SBD. i. p. 39, pi. 14. f. 116. Ma- 

 rine. Britain. Keel nearly central, 

 puncta in fom* rows. Sm. 



4* Front vieiv Innately curved. 

 N. arcuata (Greg.). — Front view 

 linear arcuate, with roimded ends ; valves 

 lanceolate, obtuse; puncta about 20 in 

 •001". Grev. MJ. Y\i. p. 82, pi. 6. f. 4-7. 

 Maiine. Scotland. 



5* Frustides straight in hotli vieivs, not 

 constricted at the middle. 



t Front -view linear. 

 N. scalaris (E., Sm.). — Large; front 

 view broadly linear, with dilated truncate 

 ends and broadly sti'iated margins, the 

 striae alternately longer and shorter; 

 valves linear with shortly attenuated, 

 obtuse ends. SBD. i. p. 39, pi. 14. f. 115. 

 = Synedra scalaris, EA. p. 137, t, 2. 2. 



