832 



SYSTEMATIC niSTORY OF THE IXFITSOEIA. 



Craspedodiscus elcf/am (E.). — Bor- 

 der with obliquely quadrate cellules; 

 disc with a central rosette of hve or six 

 oblong ones, the others being- circular 

 and somewhat radiating-, (xi. 38.) EM. 

 pi, 33. 18. f. 2. = Cosci)iocNscus eler/ans, 

 KSA. p. 126. Bermuda deposit. Frus- 

 tules large, with an elegantly marked 

 border, the diameter of which is much 

 less than that of the centre. This species 

 difters from the rest in its central rosette 

 and diagonally marked border. 



C. Coscinodiscus (E.). — Border broad, 

 but of less diameter than the centre ; 

 cellules of border large, close ; those of 

 centre minute or puncta-like, and scat- 

 tered. _ (v. 80.) _ EM. pi. 35. 16. f. 8.= 

 Pyxidicula Coscinodiscus, EB. 1844 ; Cos- 

 cinodiscus Pi/xidicula, KSA. p. 126; Br 

 JMS.viii.p.9o,pl.5. f.4. Fossil. United 

 States. 



C. microdiscus (E.). — Border very 

 broad, its diameter greater tlian that of 

 the centre ; cellules of border large, close; 

 those of centre minute, scattered. E. /. c. 

 pi. 33. 17. f. 4. Fossil. United States. 



Resembles C. Coscinodiscus, from which 

 it ditiers in its proportionally smaller 

 centre. 



Doubtful Sjjecies. 



C. ? Stella, EM. pi. 3o b. b. 4. f. 11. 

 Ehrenberg's figure represents a smootli 

 disc with a Melosira-like umbilicus, from 

 which radiate irregularly placed lines. 



C. ? Franldini, EM. pi. 35 a. 23. f. 6. 

 = Hyalodiscus suhtilis. 



C inarginatus (Bri.). — Disc with hya- 

 line margin, having about 20 rays ; re- 

 mainder of the valve minutely punctate. 

 Diam. -0037". Barbadoes deposit. Ih- 

 JMS. viii. p. 95, pi. 5. f. 7. 



C. semiplanus (Bri.). — Margin very 

 broad, faintly radiate and punctate. One 

 half of central part of the valve smooth, 

 the remainder with 4 or 5 radii. Diam. 

 •0024" to -0035". Barbadoes deposit. 

 Br. I. c. p. 95, pi. 5. f. 12. 



C. coronatus (Bri.). — Only fragments 

 of this form have hitherto been found, 

 and consequently no satisfactory specific 

 character can be given. Br. /. c. p. 95. f. 6. 



Genus ODONTODISCUS (Ehr.).— Fmstules simple, orbicular ; disc with- 

 out nodule or septa, but with dotted rays and erect teeth. Odontodiscus 

 differs from Coscinodiscus and Actinocyclus by having its disc furnished with 

 teeth, of which the others are destitute. The dots are radiate, not parallel, 

 as in Systephania. 



Odontodiscus Spica (E.). — Teeth 

 submarginal, numerous (48) ; granules 

 in radiating series. ILA.. p. 129. Fossil. 

 Virginia. Granules 19 in 1-1152". 



O. Uranus (E. ). — Disc with numerous 

 (32) radiating series of granules and 

 marginal teeth. KSA. p. 129. Fossil. Vir- 

 ginia. O. Uranus has marginal teeth and 

 fewer radiating series of granides than 

 O. Spica ; but we doubt whether they be 

 really distinct species. 



O. eccentricus (E.). — Disc with its 

 granules arranged in eccentric, curved, 

 indistinctly radiating rows ; teeth nu- 



merous, marginal, (v. 90.) EM. pi 36 a. 

 18. f. \\.= Coscinodiscus eccentricus, SD. 

 i. p. 23, pi. 3. f. 38. ? Fossil. Guano, &c. 

 Granules about 20 in 1-1152". D. 1-864". 

 This species difters from Coscinodiscus 

 only in having teeth, and may be merely 

 that state of the latter which is described 

 and figured by Professor Smith as spinous. 

 We, however, have generally failed to 

 detect the spines in the Coscinodiscus 

 eccentricus, although they are obvious 

 enough in the Odontodiscus, which is 

 usually much smaller. On these accounts 

 we cannot decide that they are identical. 



Genus SYSTEPHANIA (Ehr.). — Frustules orbicular; disc cellulose, 

 neither radiate nor septate, with an external circlet of spines or an erect 

 membrane on the disc, not on the margin ; cellules in parallel rows. '' The 

 genus has the habit of Coscinodiscus lineatus, but with lateral crowns, which, 

 in the young state, unite two individuals " (Bailey). The spines are subulate, 

 and appear not unlike the peristome of a moss. 



Systephania acideata (E.). — Disc 

 loosely cellulose ; cellides distinct, spines 

 erect, not crowded, few (12 to 15), placed 

 on the disc near the margin. KA. p. 126. 

 Bermuda. Cellules 8 in 1-1152". Diam. 

 1-324". This species is distinguished 



by its fewer spines and more conspicuous 

 cellules. 



S. Corona (E.). — Disc densely cellu- 

 lose ; spines erect, numerous (40 to 50), 

 closely set, placed on the margin. EM. 

 pi. 33. 15. f. 22. Bermuda, Virginia. 



