"748 Bacillariese, Striatellaceas, Tetracyclus. 



fossilis in Sibiria et Mexico (Ehrenberg). — Affinis T. lacuslri 

 Ralfs cujus forte varietatem sistit. 



4. Tetracyclus elllpticus (Elir.) Grun. in Wien. Verhandl. 1862, p. 411, 30ii 

 Biblar-iuin ellipliGum Ehr. in Ber. Berl. Akad. 1845, p. 74, Mi- 

 krogeol. t. 33, II, f. 5, XII, f. 2, Biblarium Rliombus Ehr. iJ Ber. 

 1845, p. 75. Mikrogeol. t. 33, II, f. 9, XII, f. 7-8, Tetracijclus 

 Rhombus Ralfs in Pritch. Inf. p. 806, Biblarium compressum 

 Ehr. in Ber. 1845, p. 73, Mikrogeol. t. 33, II, f. 2, XII, f. 1, Bi- 

 blarium Lancea Ehr. ia Ber. 1845, p. 74, Mikrogeol. t. 33, XII, 



f. 5? — Valvis elliptico-laQceolatis vel ovato-rhomboideis, latis, 

 magnitudine maxime ludentibus, 25-85 ij.. longis, apicibus subacu- 

 tis; striis transversis 2-3 in 10 ^., parallelis, pseudorhaphe indi- 

 stincta. 



Hab. fossilis in Sibiria et Oregonia (Ehrenberg). — Costa^ (vit- 

 tte seu laraellulse Ehr.) 27-28. 



5. Tetracyclus elegans (Ehr.) Ralfs in Pritch. Inf. p. 806, Grun. in 3012 

 Wien. Verhaad. 1862, p. 411, Biblarium elegans Ehr. Mikrogeol. 



t. 33, II, f. 4. — Tetracyclo lacustri Ralfs siniilis, apicibus acu- 

 tis, ventre acutius turgido. 



Hab. fossilis in Sibiria (Ehrenberg). 



6. Tetracyclus linearis (Ehr.) Gmn. ia Wien. Verhandl. 1862, p. 411, 3013 

 Biblarium lineare Ehr. in Ber. Beri. Akad. 1845, p. 74, Mikro- 

 geol. t. 33, XII, f. 6, Biblarium Lamina Ehr. in Ber. Berl. Akad. 

 1845. p. 74, Mikrogeol. t. 33, XII, f. 3-4. — Valvis lineari-oblon- 

 gis, apicibus rotundatis, passim subacutis, medio vix vel haud con- 

 strictis, 48-55 a. longis, pseudorhaphe inconspicua, striis transver- 



sis 2-3 in 10 a. 



Hab. fossilis in Sibiria et Oregonia (Ehrenberg). 



7. Tetracyclus Castellum (Ehr.) Grun. in Wien. Verhandl. 1862, 3014 

 p. 411, Biblarium Castellum Ehr. in Ber. Berl. Akad. 1845, p. 73, 

 Mikrogeol. t. 33, II, f. 1. Pritch. Inf. p. 806, t. 4, f. 44. — Valvis 

 late ovatis, obtusis, subrhomboideis, marginibus triundulatis, ad 30 



a. longis. 



Hab. fossilis in Sibiria (Ehrenberg). 



8. Tetracyclus? gibbus Ehrenb. in Ber. Berl. Akad. 1844, p. 2(55 30ir, 

 (sub Biblario). ~ Frustulis levibus, ad 25 <j.. longis, bacillaribus, 

 binis, ternis aut quaternis, mediis rectis, lateralibus medio gibbis. 



Uab. in Kurdistania (Ehrenberg). 



