OF THE NATICULE.ig. 



911 



N. Rhaphoncis = Puinularia Rhapho- 

 neis, EM. pi. .35 a. 9. f. 7. Ganges. 

 Minute, oblong', with subacute apices, a 

 small central nodule, and diverging stri;T3. 



N. eunjsoma (E.). — Minute, smootb, 

 elliptic, VN^itli rounded ends, and marked 

 by two narrow, longitudinal blank lines, 

 which converge at each end and are 

 connected at the centre by the transverse 

 nodule. EB. 1838. = Stauroneis itiry- 

 soma, EM. pi. 21. f. 3G. Fossil. Algiers. 

 Apparently more allied to the Ija-ate 

 group of Na\icula than to Stauroneis. 



Species ft'om Ehrenherg, hiown to us 

 only hy name. 



N. ceratostiyma, N. Jordani, N. Leyu- 



mcn, N. ampliilepta, N. ohUqita, N. turyida, 

 N. SencyalenMs, N. FalMandifs, N. Catha- 

 rincB, N. conspersa, N. Sarann(i>, N. aida- 

 cophcena, N. Barhadensis, N. Euryale, 

 N. lejitoceros, N. sphisropitera, N. Vibrio, 

 N. leptotei'mia, 



Pimndaria affinis, Ehrenberg gives 30 

 habitats. It may be a form of Naviada 

 affinis, with more evident strife. 



P. amhiyua, P. australis, P. insidaris, 

 P. pleuronectes, P. Preissii, P. Fasus, P. 

 Phenana, P. Craticida, P. pterophama, 

 P. platysoma, P. Catharince, P. anomala, 

 P. Hempricliii, P. Licaarce, P. Capensis, 

 P.Caffra, P. anfarctica, P. Folium, P. 

 micros2)Jienia, P. j^lewonectes, P. Arau- 

 canice, P. Barhadensis. 



Genus STAURO^^EIS (Ehr., Khtz.).— Fnistules simple, free in fi-ont view 

 parallelogramic ; valves \\ith median Line and nodules, central nodule trans- 

 versely dilated. Stauraneis differs from Na^dcula in ha^dng the central 

 nodule prolonged into a transverse pellucid band (stauros) free from stria). 

 "In a few cases we meet ^\ith the semblance of a stauros in the genus 

 Pinnularia [i^avicula] ; but in these instances a closer examination wiU show 

 that this appearance arises from the interruption of the costag merely, and 

 not from the dilatation of the central nodule, which is still found unchanged " 

 (Smith). Ehi-enberg dixides this genus into Stauroneis and Staiu'optera — the 

 former having smooth, and the latter striated frustules ; but we agree with 

 Professor Kiitzing in thinking the distinction, as in Navicula and Pinnularia, 

 unsatisfactory, and that many species would be referred by the observer to 

 the one or other genus according to the magnifying power of the microscope 

 used in the examination. 



S. Leyumen (E.). — Small, oblong- 

 lanceolate, each margin with three uii- 

 didations; apices apicidated ; stauros 

 linear, reaching the margin. EB. 1844, 

 p. 135 j EM. pi. 39. 3. f. 104; Greg. 

 MJ. iv. pi. 1. f. 9. = Stauroneis linearis, 

 SD. i. p. 60, pi. 19. f. 193. America, 

 Europe. 



* Valves constricted at the centre. 



SxAunoisrEis constricta (E.). — Small, 

 oblong, deeply constricted at the centre, 

 and slightly contracted into obtuse 

 apices. EA. p. 134, pi. 1. 2. f. 12 6. 

 Chili, Australia, Africa. 



S. Rabenhorstii. — Linear, mth broadly 

 rounded ends and concave sides; costse 

 stout, oblique; stauros linear. = Stattro- 

 ptera constricta, Rab D. p. 50, pi. 9. f. 10. 

 Italy. 



2* Valves with 2 or S imdidations. 



S. injlata (K.). — Small, linear, with 

 tvro constrictions, and three dilatations; 

 ends broadly roimded; stauros linear, 

 reaching the margin. KB. p. 105, pi. 30. 

 f. 22. Trinidad. 1-480" to 1-428". 



S. FulmeniVtvoh.). — Lanceolate, acute, 

 with two undulations; stauros ver}^ 

 slightly dilated towards the margin ; 

 strife distinct, 22 in -001" ; front view 

 rectangular. -008" to -015". TM. vii. 

 p. 180, pi. 9. f. 6. Fresh water. Mel- 

 bourne. This beautiful species resembles 

 S. acuta, but is easily distinguished by 

 its marginal undulations. 



(\Ti. 67.) 

 3* Vcdves with a siymoid median line. 



_ S. Siyma^ (E.). — Stout, lanceolat.-, 

 sigmoid, with obtuse apices : stauros 

 abbreviated. EB. 1844, p. 88 ; EM. 

 pi. 18. f. 63. Fossil. Eichmond deposit. 

 It has the form and size of Pleurosiyma 

 acuminatum', but its median nodule is 

 dilated, as if geminate. 1-240". Ehr. 



S. obliqua (Greg.). — Small, short, ob- 

 long, or broadly lanceolate, with a sigmoid 

 or oblique median line ; stauros reachino* 

 the margin ; stria3 fine, 45 in -001". MJ. 

 iv.p. 10, pi. 1. f.35. Lochleven. (vii.63.) 



4* Valves with rostrate or capitate 

 apices. 



S. dilatata (E.).— SmaU, ventricose, 

 \A\\\ minute, mammiform beaks ; stauros 



