OF THE NAYICULE^. 



915 



slightly produced, mammiform apices ; 

 surface punctato-striate, with a large 

 smooth central space. BMO. p. 40, 

 pi. 2. f. 32. Florida. Resembles -S: 

 punctata, K., but is larger, and has the 

 ends not so much produced. The figiu-e 

 shows a dilated umbilical space rather 

 than a true stauros. 



S. scalaris (E., K.). — Small, linear- 

 oblong, with roimded ends -, costto stout, 

 parallel, 12 in 1-1200", not reaching the 

 median line. KB. p. 10Q. = Stauroptera 

 scalaris, EA, pi. 4. 2. f. 3. Labrador, 

 (xii. 10, 14, 30.) Scarcely belonging to 

 this genus, since Ehrenberg's figures show 

 a definite central nodide. It diiFers from 

 Navicula horealis by its coarser costae and 

 their inteiTuption opposite the median 

 nodide. 



S. amp1iioxys = Stam'optera amphioxys, 

 EM. pi. 6. 1. f. 14. Fossil. Santa Fiore. 

 Ehrenberg's figure represents an elon- 

 gated, narrow-lanceolate Navicula, with 

 acute apices^ and a minute central nodule 



I which is not dilated into a stam-os ; striae 

 radiant. <« 



I S. peregrina = Stauroptera peregrina, 



\ EM. pi. 6. 1. f. 15. Fossil. Santa Fiore. 

 Ehrenberg's figure represents a small, 



I lanceolate Navicida, with a minute 

 central nodule, but no stauros ; striae 



! radiant. 



I S. ? ovalts (Greg.). — Small, smooth, 

 oyal ; stam'os broad, indistinct, reaching 

 the margin. MJ. iv. p. 11, pi. 1. f. 36. 

 Britain. Perhaps a Cocconeis. 



; Species fro7n JElirenhei^g known to us 

 only hy name. 



S. pusilla, S. splicerophoron, S. Indica, 

 S. Placentida, S. Hologramma, S. gihhosa, 

 S. JEthioinca, S. A^njjhisbcpna, S. Capensis, 

 \ S. GaJapagica, S. decurrens, S. hrevirostris, 

 ; Stauroptera nohilis, Stauroptera leptoce- 

 pluda, Stauroptera Distauridiwn, Stau- 

 roptera Braziliensis, Stauroi^tera Tabel- 

 laria, S. asperula, Staurojytera Siamensis, 

 } Stauroptera trinodis. 



Genus STAUROGRAMMA (Rab.). — Like Staiironeis, but with decussating 

 strioe, and prominent knots at the intersections, Rab. 



Stauhogramma Persicum (Rab.). — median line dilated towards the ends. 

 Oblong-lanceolate, with trmicate apices ; Rab D. p. 50. = Stauroptera decussata, 

 stam-os linear, reaching the margin; Rab D. pi. 9. f. 14. Persia, (vin. 36.) 



Genus PROROSTAUROS (E.). — Frustules simple, free ; with the cha- 

 racters of Stauroneis, except that its terminal puncta in the front \iew are 

 approximate and not lateral. We doubt whether this genus can be separated 

 from Stauroneis ; for, if we understand Ehrenberg's definition, the apparent 

 position of the terminal puncta depends upon the greater convexity of the 

 lateral valves, which therefore appear, in the front view, like a border on 

 each side of the connecting zone, and the puncta are within the angles. The 

 species are unknown to us. EB. 1843, p. 136. 



PROROSTAUROS spkndens (E.).— River I P. ? suhulatus ? (E.).— Senegal, Cape of 

 Senegal. Good Hope. At first sight it reminds 



I one of Gomphonema gracile, E. 



Genus PLEUROSIPHONIA (E.). — The characters of this genus are 

 unknown to us ; but, from Ehrenberg's figure of P. affinis, we think it is 

 probably identical with Mastogloia. 



Pleurostphonia affinis (E.). — Ob- 

 long-lanceolate, with capitate ends, me- 

 dian line and nodules, and a marginal 

 band of transverse striae. EB. 1856, 

 p. 32. = Fragilaria Navicula, E. 1841 ; 

 EM. 33. 1. f. 14. Arabia, Africa, Pern. 



Species knoivn only hy oiame. 

 P. Amphishoena (E.), Ai*abia, Africa, 

 Peru, Mexico ; P. fulva (E.), Arabia, 

 Africa; P. Phcenicenteron (E.), Arabia, 

 Africa ; P. Lihyca (E.), Africa ; P. ohtusa 

 (E.), Africa ; P. gracilis (E.) Afiica. 



Genus PLEUROSIGMA (Smith) (Gyrosigma, Eassall, Babenhorst, &c.). 

 — Frustules simple, free, elongated ; front view linear or lanceolate, narrower 

 than the lateral view ; valves depressed or slightly convex, sigmoid (rarely 



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