OF THE CYMBELLE^. 



875 



formly curved, with truncate ends and 

 striated margin. 



A. ? incequalis (E.). — Unequally bent 

 and smooth. EM. pi. 16. 1. f. 45, & 

 pi. 17. 2. f. 25. Fossil. Sweden, Finland. 



A./^ jjaradoxa (E.). — Frustules ovate, 

 obtuse, twice as long as broad, with 16 

 transverse, scabrous, pimctated lines in 

 1-1152". ERBA. 1845, p. 73. Fossil. 



United States. 1-900". No nodule ob- 

 served, E. 



Species known to us only hy name. 



A. turgida (E.), Australia, America ; 

 A. Indica (E.), India; A. Javanica (E.), 

 Java; A. ohtusa (E.j, Africa; A. Semen 

 (E.), America; A. Brasiliensis (E.), Bra- 

 zil ; A. incrasscda (E.), America. 



Genus CYMBOSIRA (Kiitz.). — Frastules as in Achnanthes, stipitate, con- 

 nected into series by a gelatinous process or hinge (isthmus). CjTnbosira 

 differs from Achnanthes by the same character as Diatoma from Fragilaria. 



Cy]MB0Slra Af/ardhii (K.). — Frus- 

 tules linear, slightly cmwed, with rounded 

 apices; valves linear, oblong, scarcely 

 dilated at the middle, \N'ith rounded 



obtuse apices. KB. p. 77, pi. 20. f. 3. 

 = Achnanthes seriata, AgCl). Marine. 

 Venice, Cayenne, (xiv. 14.). 1-960" to 

 1-288". Stipes very short. 



Genus MONOGEAMMA (Ehr.). — Frustules fiu^nished with transverse pin- 

 nules, a median, transverse, linear band on one valve only, three ventral 

 nodules and two dorsal. ( = Stauroptera with a stam^os on one valve only, or 

 to a solitary Achnanthes with terminal pimcta. — ERBA. 1843, p. 136.) Not- 

 withstanding Ehrenberg's remarks, we cannot dLstinguish this genus from 

 Achnanthidium. The species are known to us only by name. 



MoNOGRAirNiA Achuanthes (E), India. 

 M. trinodis (E.), Sandwich Islands. 



M. ventricosa (E.) 

 tricosa. 



Achnanthes ven- 



FAMILY XVI.— CYMBELLE^. 



Frustules cymbiform; valves lunate, with a longitudinal line, and mar- 

 ginal or subcentral nodule. In shape the Cymbellese are very similar to the 

 Eunotieae, but they differ essentially both from them and the Naviculeee by 

 the median nodules of the lateral surfaces being marginal or submarginal. 



Genus CYMBELLA (Ag., Kiitz.). — Frustules free, C3'mbiform ; transverse 

 striae interrupted by a longitudinal line having central and terminal nodides, 

 and di\iding the valve into unequal portions. The frustules, in the lateral 

 view, have one margin (dorsum) convex, and the other (venter) straight, or 

 at least less developed. In consequence of this form, the longitudinal line 

 divides the surface unequally, being much nearer the lower margin. CymbeUa 

 includes species distributed in the genera Cocconema, Navicula, and Pinnu- 

 laria of Ehrenberg's system. 



* Valves ii'ith one margin triundulate. 



CY:yiBELLA Areas (Greg.), — Valves 

 slender, semilanceolate, with straight 

 venter, convex, triundulate dorsum, and 

 produced, minute, capitate apices. Greg, 

 in MJ. iv. p. 6, pi. 1. f. 21 ; SBD. ii. 

 p. 85. Scotland. Minute ; longitudinal 

 line and nodules submarginal ; transverse 

 stri« very fine, 40 in -001". [ VU . JV 



C. sinuata (Greg. J. — Valves lanceolate, 

 with subcapitate apices, gently convex 

 dorsum, and triundulate venter. Greg. 

 MJ. iv. p. 4, pi. 1. f. ]7. Scotland. 

 Minute ; transverse striae conspicuous. 



about 20 in -001", scarcely reaching the 

 median line. 



2* Valves without triundulate margins. 



t Valves with produced or capitate 

 j apices. 



I C. Ehrenhergii (K-)- — Yalves broadly 

 I lanceolate, -«4th imequal sides, suddenly 

 I contracted into rather obtuse, slightly 

 I produced apices ; transverse strise di- 

 stinct, punctate, 12 in 1-1200". KB. p. 79, 

 t. 6. f. 11 ; SBD. i. p. 17, pi. 2. f. 21. ^Na- 

 vicida incequalis, E Inf. t. 13 ; Timndaria 

 incequalis, EM. many figures. Common, 



