790 



SYSTEMATIC HISTOEY OF THE IKFTJSOEIA. 



Desmogonium Gmanense. — EM. t. 34. 

 5 A. f. 3. Apparently not very uncom- 

 mon, since Ehrenberg gives about 50 

 habitats in Asia, Africa, and America. 



(xv. 13.) Frustiiles not stipitate; valves 

 Tvitliout longitudinal ridges, mostly 

 broader than the front view. 



Genus DIMEREGRAMMA (N., G.). — Fnistiiles quadrangular, two or more 

 together; valves scarcely broader than front ^dew, having the transverse 

 costae or strige interrupted by a smooth, longitudinal median line. The frus- 

 tiiles are united as in Denticula or Odontidium, from which genera it is 

 distinguished by the longitudinal median line. The structure is probably 

 the same as in Staui'osira (E.), the description of which, however, is altogether 

 inapplicable to many of the species here assembled. 



DiMEEEGRAMMA miiior (Greg.). — 

 Front view with convex striated margins, 

 constricted beneath the conic angles ; 

 valves narrow lanceolate, A\dth from 18 

 to 20 strong costae in -001" . = De?iticula 

 mbior, GDC. p. 23, pi. 2. f. 35. Marine. 

 Scotland. 



D. capitatmn (Greg.). — Front view 

 vnt\\ convex, obscurely striated margins, 

 constricted beneath the dilated roundish 

 a])'ices. = Denfictdaf a capiUda, Greg I.e. 

 p. 22, pi. 2. f. 31. Marine. Scotland. 

 Is larger than D. namim, with roimded 

 apices. Side view unknown. 



D. nanmn (Greg.). — Front ^dew with 

 convex margins, constricted beneath the 

 conic angles ; valves broad, obtusely 

 rhomboid, Tvith rather fine striae. =i)e;i- 

 ticida nana, Greg I. c. p. 23, pi. 2. f. 34. 

 Marine. Scotland, (iv. 33.) 



D. distans (Greg.). — Front view con- 

 stricted beneath the conic angles ; valves 

 broad, rhombic-lanceolate, with strong, 

 short marginal costae, and a lanceolate, 

 blank median s-^ace. = Deidicida distans, 

 Greg I.e. p. 23, pi. 2. f. 36. Marine. 

 Scotland. Is larger than I), minor, and 

 its valves broader, (iv. 34.) 



D. Rhombus = Fragilaria ? Rlwmhus, 

 EM. pi. 8. 1. f. 16. Fossil. Hungary. 

 Valves broadly rhomboid, with marginal 

 costae, and a smooth median space. 



D. fidnim (Greg.). — Front view elon- 

 gated, with striated margins, constricted 

 beneath the dilated apices ; valves nar- 

 row lanceolate, with dilated, subcapi- 

 tate apices ; striae monilifonn, nearly 

 reaching the centre. = Dentieula fidva, 

 GDC. p. 24, pi. 2. f. 38. Marine. 'Scot- 

 land. 



D. marinum (Greg.). — Front view 

 elongated, linear, with striated margins 

 and slightly produced angles; valves 

 linear, yvith. gibbous middle, obtusely 

 conic apices, and about 10 coarsely 

 monilifomi striae in -001" . = Dcfdiada 

 marina, Greg /. e. p. 24, pi. 2. f. 39. 

 Marine. Scotland. 



j D. midahile (Sm.). — Filaments elon- 

 gated ; valves oblong or lanceolate, with 

 20 marginal costae in -001". = Odotdidium 

 mufabile,SBJ). ii. p. 17, pi. 34. f. 290; 

 Frac/ilaria amjjiiioxys, EM. pi. 39. 3. 

 f. 53. Fresh water. Europe. 

 I D. Leptoceros (E.). — Valves rhomboid- 

 linear, with longly attenuated, acute, 

 straight ends, finely striated margins, 

 and a smooth median s^ace.= Fragilaria 

 Leptoceros, EEBA. 1844, p. 82 ; Odonti- 

 dium Leptoceros, KSA. p. 13. North 

 America. 



D. sinuatiim (Thwaites). — Front view 

 linear, truncate ; valves rhomboid-lan- 

 j ceolate, with slightly uudidated margins ; 

 j striae delicate, 52 in -001" ; costae inter- 

 rupted, 10 in -001". = De?dieuIa sinuata, 

 SBD. ii. p. 21, pi. 34. f. 295. Fresh 

 water. Britain, (w. 12.) 



D. Tahellaria (Sm.). — Filaments fra- 

 gile ; A^alves with constricted or inflated 

 middle, rostrate apices, and 36 delicate 

 costae in -001". = Odontidium Tahellaria, 

 SBD. ii. p. 17, t. 34. f. 291. a, valves 

 inflated at the m\&dlQ, = Staurosira con- 

 siruens, Eh. ? /3, valves constricted at 

 the middle, (iv. 35.) 



D. hirostris (E.). — Very minute; valves 

 lanceolate, suddenly rostrate, acute; 

 strii© interrupted by a median line.= 

 Fragilariahirostris, ERBA. 1844, p. 342; 

 Microg. pi. 38 a. 2. f. 8. Fossil. Ger- 

 many. 1-3120". Has nearly the cha- 

 racters of a Staurosira, Fh. 



D. informe (S.). — Valves elliptical, 

 with an" irregular inflation at the centre, 

 and hence subcruciform ; costae 18 in 

 •001."= Odontidium informe, S Annals, 

 1857, p. 10, pi. 1. f. 12. Fresh water. 

 France. 



D. Harrisonii (Sm.). — Frustules fre- 

 quently adhering by their angles ; valves 

 cruciform, with rounded lobes ; costae 



distinct, 13 in -001". 



Odontidium ? 



Harrisonii, SBD. ii. p. 18, pi. 60. f. 373. 

 Fresh water. Hull. The valves in fonu 

 resemble those of a small Tetracyclus, 



