OF THE EUNOTIE^. 



763 



ERBA. 1845, p. 77, & M. pi. 33. 12. f, 13. 

 Fossil. Oregon. 



E. Sima (E.). — Valves linear, slightly 

 curs^ed, -wdtli rather concave venter j 

 dorsum suddenly sloping down to the 

 produced, acute, reflexed apices. ER 

 BA. 1845, p. 77, & M. pi. 33. 12. f. 16. 

 Fossil. Oregon. 



E. biceps (E.). — Valves linear, curved, 

 with dilated, slightly revolute, broadly 

 rounded ends. EA. p. 125, k M. pi. 5. 2^ 

 f. 36. Europe and America. Some at 

 least of Ehrenberg's figures in the ' Mi- 

 crogeologie' belong to Synedra jiexuosa. 



E. Alpina (K.) = HimanticUum Hal- 

 cy o)ieIl(B (Vevty). — Valves with turgid 

 convex dorsum, slightly produced sub- 

 truncate apices, and verv fine transverse 

 strife. KB. p. 36, t. 3. £ 10. S^^dtzer- 

 land. 



E. incisa (Greg.). — Valves arcuate, 

 slender, with obtuse or subacute apices, 

 and subterminal notches or depressions 

 on the ventral margin ; strife fine, 44 in 

 •001". Greg MJ. vol. ii. p. 96, pi. 4. 

 f. 4. Lapland, Scotland. 



E. Plectrum, EM. pi. 6. 2. f. 15. 

 Fossil. Sweden. Valve semilunate, con- 

 stricted beneath the capitate apices ; 

 venter straight ; dorsum evenly convex. 



E. Hemicyclus (E.). — Small ; valves 

 linear, curved, semicircular, with obtuse 

 apices and distinct ti-ansverse striae. = 

 Synedra Hemicyclus, ERBA. 1840, & 

 M. t. 16. = E. Falx, Greg MT. vol. ii. 

 p. 105 ; MJ. vol. iii. pi. 4. f. 1. Fossil. 

 Sweden. 



2 * Valves with two dorsal and three 

 ventral undulations. 



E. Crocodilus (E.). — Valves elongated, 

 slightly cm'ved, with two dorsal and 

 three ventral undulations; apices pro- 

 duced, subacute, reflexed. ERBA. 1845, 

 p. 77 ; M. pi. 34. 5 a. f. 4. Africa and 

 America. 



E. Tapacumae, EM. pi. 34. 5 a. f. 5. 

 America. Valve with two dorsal and 

 three ventral undulations separated by 

 deep sinuses; apices abruptly produced 

 into a short beak. E. Tapacumae seems 

 to differ from E. Crocodilus in its stouter 

 form, deeper sinuses, and more abruptly 

 produced apices. 



3 * Valves with detitate or crenate 

 dorsum. 



E. Camelus (E.). — Valves striated, 

 small; dorsmn with two approximate 

 rounded elevations, sloping to the atte- 

 nuated, produced, obtuse apices. EA. 



p. 125, t. 2. 1. f. 1. Asia, Africa, and 

 America. 



E. hidentula (S.). — Valves faintly stri- 

 ated, with two prominent, acute or 

 rounded dorsal ridges, very straight 

 ventral margin, and obtuse, produced 

 apices. SBD. vol. ii. p. 83. E. Camelus, 

 Grev ANH. 2nd series, vol. xv. pi. 9. f. 1. 

 Britain. Differs from E. Carnelus in its 

 straight ventral margin. 



E. Sella (E.). — Valve dilated ; ventral 

 margin straight; dorsum with two central 

 ridges, from which it passes with a re- 

 gular convexity to the acute apices. 

 EA. p. 126, t. 2. 1. f. 7. America. 



E. Zygodmi (E.). — Valves linear ; dor- 

 sum with two approximate ridges, from 

 which it passes by a curvatm-e to the 

 rounded apices. EA. p. 127, t. 2. 1. f. 6. 

 America. 



E. declivis (E.). — Valves wdth plane 

 venter ; dorsum convex, with two ridges 

 which slope to the acute apices, EA. 

 p. 125, t. 2. 1. f. 3. America. 



E. impressa, EM. pi. 2. 2. f. 30, »S:c. 

 America. Small, striated; valves nar- 

 row, linear, with two slight dorsal im- 

 dulations and obtuse ends. Perhaps a 

 bicrenate state of E. tridentula. 



E. hactriana, EM. pi. 16. 1. figs. 29, 

 30, & pi. 16. 2. f. 19. Fossil. ^ Sweden. 

 This seems a distinct species, with linear, 

 nearly straight valves, and two remote, 

 minute dorsal teeth. 



E. f/^Wow (E.). — Valves stout, with 

 two rounded dorsal ridges and broadly 

 rounded ends; strise distinct, radiant. 

 E Inf p. 192, t. 21. f. 23; SBD. pi. 2. 

 f. 17. Recent and fossil. Europe, Asia. 

 Africa, and America. — This and the thir- 

 teen following species of Ehrenberg we 

 regard as mere varieties, which differ only 

 in the number of their dorsal elevations. 

 The species may be called E. robusta : 

 its valves are stout, semilunate, wdth 

 concave venter, broadly rounded ends, 

 turgid convex dorsum fm*nished with 

 conspicuous, roimded, diverging ridges, 

 and the strise are strongly marked and 

 highly radiant ; as, however, the valves 

 increase in length, according to the in- 

 creased number of dorsal ridges each is 

 comparatively more slender than its pre- 

 decessor, and the ridges are smaller and 

 resemble crenations. 



E. triodon (E.). — Has three dorsal 

 ridges; otherwise resembles E. diodon. 

 E Inf. p. 192; SBD. pi. 2. f. 18. Recent 

 and fossil. Em-ope, Asia, Africa, and 

 America, (iv. 4; ix. 164.) 



E. tetraodon, E., Sm., K., Rab. ; E. 

 pcntodon, E,, K. ; E. Eiadema (6 ere- 



