144 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



RUTILARIA TENUICORNIS Grunow 



(Van Heurck, Synopsis, pi. 105, fig. 10.) 



Van Heurck hints at the possibility of this being a variety of R. epsi- 

 lon Greville, and De Toni (Syl. Alg., p. 1021) takes that view of it. 

 I dissent. R. epsilon is lightly and irregularly marked with crude 

 blotches or beads and tapers gradually from the enlarged middle 

 portion to the apices; R. tenuicornis is regularly marked with fine 

 beading, has a relatively much larger middle portion which curves 

 rapidly to the long, narrow, and almost parallel-sided arms. The 

 peculiar lock catch, which joins each frustule with the next and 

 resembles the Greek letter epsilon, is not confined to either of these 

 species, but is general with the Rutilariae. (Compare Greville, Micro. 

 Journ., 1863, pi. 9, fig. 1 ; R. radiata Grove and Sturt in Schmidt, Atlas, 

 pi. 183, fig. 22, etc.) 



Genus SCEPTRONEIS Ehrenberg 



SCEPTRONEIS CUNEATA Grunow 



Plate 31, fig. 4 



(Grunow, Diat., Hondu., p. 169, pi. 194, figs. Sa-d; Peragallo, Diat., France, 

 pi. 78, figs. 1-2.) 



Peragallo removes this diatom to Synedra, where it probably belongs. 

 But I have retained its orginal name because cuneate forms like this 

 can be with about equal justice referred to Licmopliora. A girdle 

 view of this diatom would settle this, according as it proves to be 

 wedge-shaped or not. 



Genus SCOLIOPLEURA Grunow 



SCOLIOPLEURA PARTISTRIATA, new species 



Plate 31, fig. 5 



Valve broad linear, barely sigmoid, with pointed ends; hyaline 

 median area conspicuous, strongly sigmoid, bisected b the delicate 

 rhaphe; central nodule large; markings of strong, transverse, closely 

 set costae, terminating in beads next to the median area, each costa 

 having a large bead at the middle, the single row of larger beads 

 thus formed running parallel to the rhaphe. 



Length 0.145; width 0.021; 5.2 lines in 0.01 mm. 



This is distinguished from S. latestriata (Brebisson), Grunow, as 

 well as from the questionable S. thumi H. Heiden (Schmidt, Atlas, 

 pi. 261, figs. 1-3) by both of these having double rows of zigzag bead- 

 ing and peculiarly marked borders on each side of the median area. 

 Cleve's creation of the new genus Scoliotropis for these forms and his 

 assignment of S. tumida (Brebisson) Rabenhorst to Navicula are not 

 to be commended. 



Type.— -Cat. No. 43679, U.S.N.M. 



