940 



SYSTEMATIC HISTOEY OF THE IN-FUSOEIA. 



For Craspedodiscus coj'onatus, substitute the following : — 



Genus BRIGHTWELLIA (Ealfs, n. g.).— Disc with a large granulated 

 centre, separated from a broad punctated limb bj a circlet of oblong cellules. 



"VVe have constituted this genus to receive a beautiful Diatom placed by Mr. 

 Brightwell in Craspedodiscus, but which differs so greatly from other Diatoms 

 that we believe it should form the type of a new one, which, with much plea- 

 sure, we dedicate to the author of the excellent monographs of Triceratium 

 and the Chgetocerege. 



Brightwellia coronata (Bri., Ralfs). 

 — Central portion of valve with an 

 irregular blank umbilicus and radiating 

 series of granules, which are closer and 

 in curved lines near the circlet of cellules. 

 = Craspedodiscus coro7iatus, Bri JMS. 

 viii. p. 95, pi. 5. f. 6. Barbadoes deposit. 

 This species is very variable in size. In 

 a dry state it is of a purplish or brown 

 colour, but in balsam hyaline; the centre 

 has the gramdes irregular near the imi- 



bilicus, and interrupted by blank rays; 

 but near the circlet of cellules they be- 

 come more regular, and form curved, 

 moniliform lines. The broad limb is 

 usually brownish when dry, and marked 

 by numerous radiating lines, similar to 

 those of Coscinodiseus conci?i)ius, and 

 have in the intervals extremely minute 

 obliquely arranged granules. The radi- 

 ating lines, although conspicuous in the 

 dry statC; nearly disappear in balsam. 



After Cymatopleuba Ovtwi (p. 793), insert : — 



C. multifasciata (Kiitz.). — Valves 

 linear, with acutely cuneate apices, and 

 very fine transverse strise. = Surirella 

 multifasciata, KB. p. 60, pi. 3. f. 47. 

 Europe. 



C. therynaUs (Kiitz.). — Slightly pan- 

 duriform, otherwise as in C. multifasciata. 

 = Surirella thermalisj KB. p. 60, pi. 3. 

 f. 46. Europe. 



Genus CYLINDEOTHECA (Rab.).— Frustules exactly cylindrical, with 

 percurrent spires, and imbedded in an amorphous, gelatinous mucus. 



CYX,iNi)R0THECA(xers^e«5er^en(Rab.). I (rarely one or three) spires. Rab. Algen 

 — ^Frustules lanceolate, acute, with two | Sachsens, No. 801. Dresden. 



Note. — Mr. Ralfs originally proposed to introduce a family Synedreae, as 

 mentioned in p. 758, but subsequently transferred the genera to the family 

 Surirelleae, the genera in which he distributes thus : — 



* Frustules hacillar ; valves keeled — Nitzschie^. 

 Genera. Nitzschia, Ceratoneis, Amphipleura, Bacillaria, and Homoeocladia. 



2* Frustules hacillar; valves scarcely broader than front view, not heeled — 



Synedre^. 



Genera. Synedra, Desmogonium, Dimeregramma, and Staurosii-a. 



3* Frustules not hacillar; valves mostly hroacler than front view, not heeled — 



Surirelle^. 



Genera. Rhaphoneis, Tryblionella, Cymatopleura, Surirella, Campylodiscus, 

 and Calodiscus. 



