DIATOMACE^. 



[ 255 ] 



DI ATOM ACE /E. 



[Sphcnella. Fr. free, solitaiy, wedge- 

 shaped, involute; freshwater (PL ]9. 



fig- 19)- 

 Sphcnosira. Fr. united into a straight 



filament ; v. wedge-shaped, at one end 

 rounded, suddenly contracted and pro- 

 duced ; freshwater (PI. 17. fig. 2G).] 

 Coh. 11. Navicule^. Fr. free, straight ; 

 V. equilateral, or sometimes sigmoid. 



Naviciila. Fr. single, free, straight; v. 

 oblong, lanceolate or elliptical, with & 

 median line, a central and two termi- 

 nal nodules, and transverse or slightly 

 radiant lines resolvable into dots ; 

 freshwater, marine, and fossil (PI. 15. 

 fi^s. 6-9). 



{Stigmaphora.) 



PleurosH/ma. Fr. those of Kavkida, but 

 valves sigmoid ; freshwater and marine 

 (PI. 15. figs. 10-38). 



{Toxonidea.) 



Pinmdaria. Fr. those of Kavicuht, but 

 transverse lines continuous and not re- 

 solvable into dots ; freshwater and ma- 

 rine (PL 15. figs. 1-5). 



Stauroneis. Fr. those of Navicula, but 

 the median nodule replaced by a stau- 

 ros; freshwater and marine (PL 15. 

 figs. 43-45). 



Stmirosigma. Fr. those of Staitro7ieis, 

 with a sigmoid longitudinal line. 



Diailesmis. Fr. those of Navicula., united 

 into a straight filament; freshwater 

 (PL 16. fig. 27). 



Amphiprora. Fr. free, solitary or in 

 pairs, constricted in the middle ; v. 

 with a median keel, and a median and 

 terminal nodules, often twisted ; marine 

 (PL 16. fig. 8). 



(DonMnia.) 



Ampihora. Fr. plano-convex, elliptical, 

 oval or oblong, solitary, free or adnata, 

 with a marginal line and a nodule or 

 stauros on the flat side; freshwater 

 and marine (PL 16. figs. 10, 11). 



Perizonium. Frustules navicular, free, 

 with thickened zones (PL 51. fig. 42.) 



Tribe EE. Vitiates. Fr. witb vittae. 

 t Valves withotct a median nodide. 



Cob. 12. LicMOPHOEE^. Fr. cimeate; 

 vittae arched. 

 Licmophora. Fr. cuneate, rounded at tbe 

 broad end, radiating from a branched 

 stalk ; vittai curved (formed by inflec- 

 tion of the upper margins of the valves) ; 

 marine (PL 17. fig, 3), 



Podosphenia, Fr. those of Licmophora 

 but single or in pairs, sessile upon a 

 thick but little-branched pedicel ; ma- 

 rine (PL 17. fig. 17). 

 Rhipidophoi-a. Fr. those of Licmophora, 

 single or in pairs, upon a branched 

 stipes ; marine (PL 17. fig. 19). 

 Climacosphenia. Fr. cuneate, rounded at 

 the broad end, divided into loculi by 

 transverse septa or vittae ; marine (PL 

 25. fig. 9). 

 Coh, 13. Steiatelle.?:. Fr. tabular or fila- 

 mentous; vittae straight (not arched). 

 Striatella. Fr, compoimd, stalked at one 

 angle ; vittae longitudinal and conti- 

 nuous ; V. elliptic-lanceolate, not stri- 

 ated (ord. ilium.) ; marine (PL 17. fig. 

 20). 

 Phabdonema. Fr. as in Striatella, but 

 vittae inten-upted, and v. with trans- 

 verse granular striae ; marine (PL 17. 

 fig. 18). 

 Tetracycliis. Fr. compound, filaments 

 compressed ; vittae alternate, interrup- 

 ted ; V. inflated at the middle ; costae 

 transverse, continuous ; freshwater (PL 

 17. fig. 28). 

 Tahellaria. Fr. united into a filament, 

 svibsequently breaking np into a zigzag 

 chain ; vittae interrupted, alternate ; v. 

 inflated at the middle and ends ; fresh- 

 water (PL 17. fig. 27). 

 [Pleiirodesmiwm. Fr. tabular, united into 

 a filament, and with a transverse me- 

 dian hyaline band ; marine. 

 Hyalosira. Fr. tabular, fixed by a stalk 

 at one angle ; vittae alternate, inter- 

 rupted, bifurcate at the end; marine 

 (PL 17. fig. 1). 

 Anaidus. Fr. rectangular, single, com- 

 pressed, with lateral inflections, giving 

 the valves a ladder-like appearance ; 

 marine (PL 18. fig. 7). 

 Bihlarium. Fr. as in Tetracyclus, but 

 single ; fossil (PL 50. fig. 39 ; PL 18. 

 figs. 35-48). 

 Terpsinoe. Fr. tabular, obsoletely stalked, 

 subsequently connected by isthmi ; 

 vittae transverse, short, interrupted 

 and capitate ; freshwater and marine 

 (PL 25. fig. 10 ; PL 19. fig. 3.3). 

 StylobihUi(m. Fi\ compound; v. circu- 

 lar, sculptured with continuous striae ; 

 fossil (PL 18, fig. 50).] 



tt V- lovth a median apparent (^pseudo-) 

 nodide. 



Grammatophora. Fr. at first adnatej 



