Bacillarieae, Naviculacese, Rhoicosigma. 269 



4. Rhoicosigma falcatum (Donk.) Grun. in Hedwigia 1867, p. 20 (no- H28 

 men), Perag. Pleuros. t. 9, f. 25-27, Toxonidea falcata Rabenh. 



Fl. Eur. Algar. I, p. 244, Pleurosigma falcatum Donk. in Micr. 

 Journ. 1861, p. 7, t. I, f. 1. — Valvis linearibus, valde elongatis, 

 150-175 s 15, leviter sigmatoideis, apicibus obtuso-rotundatis, facie 

 connectivali arcuato-falcata ; rhaphe e centro subabrupte marginali, 

 nodulo centrali parvo, rotuudato; striis delicatissimis. 



Hab. ad oras Anglias (Cresswell); in sinu Neapolitano Italise 

 (Barbo sec. Castracane). 



5. Rhoicosigma robustum Grun. in Cl. et Grun. Arct. Diat. p. 58 im 

 (sub Pleurosigmate), Perag. Pleuros. t. 10, f. 23. — ■ E maximis, 

 valvis longe lanceolatis, valde sigmoideo-incurvis, 440-600 s 56-62, 

 rhaphe apices versus excentrica, nodulo centrali oblongo ; striis 

 transversis 10 l / 2 , longitudinalibus 12 in 10 u. 



Hab. ad insulas « Samoa », raro; ad insulas Gallapagenses (Cleve); 

 ad insulas Balearicas, raro (Cleve). — Var. inflexum Perag. in litt. 

 et Pleuros. t. 10, f. 4: typo angustius, magis sigmoideum, apici- 

 bus acutioribus. Cura typo. 



6. Rhoicosigma mediterraneum Cleve in Grun. Micr. Journ. 1877, 1130 

 p. 182, Cleve On sorae new or little known Diatoms p. 6, t. I, 



t. 9, Perag. Pleuros, t. 9, f. 29-32. — Valvis anguste lanceolatis, 

 120-210 s 22,5, apicibus acutis, rhaphe in priraa tertia parte valvae 

 longitudinis (a nodulo centrali) valde incurva, dein recta ; striis lon- 

 gitudinalibus subtilissimis, circiter 27 in 10 u, transversis 18'/ 2 

 in 1.0 u. 



Hab. ad insulas balearicas, raro (D. Soederlund). — Var. cal- 

 careum Brun in Perag. Pleuros. t. 9, f. 28 et in litt. : typo angu- 

 stius, apicibus truucatis, rhaphe minus excentrica, striis transversis 

 subtilioribus 20 l / 2 in 10 u. Fossile in calcaria ad (( Sendai » Japonite. 



7. Rhoicosigma Antillarum Cleve Diatoms from the West Indian Ar- H3i 

 chipelago p. 9, t. II, f. 14, Perag. Pleuros. t. 10, f. 1. — Valvis 

 425 U: longis, rhaphe sigraoidea in una dimidia parte valvse valde 

 elevata quasi cristam efficiente, in altera depressa; striis distinctis 

 transversis 14-15 in 10 u. 



Hab. ad insulas Virginum, raro (P. T. Cleve). 



8. Rhoicosigma ? tahitiense (Castr.) Perag. Pleuros. tab. 10, fig. 9, 1132 

 Pleurosigma tahitense Castr. Diat. Challenger p. 38, t. 28, f. 4, 

 Notarisia 1889 pag. 691, Perag. Pleuros. t. 2, f. 10 non Witt. — 

 Valvis lanceolatis, 145=;28 u. (ex icone), gradatim ad apices acuto- 



