840 



SYSTEMATIC HISTORY OF THE INFUSOEIA. 



we woiild separate into two species all 

 those forms in which the compartments, 

 irrespective of their number, are di- 

 stinctly^ cellulose without any particular 

 arrangement of their cellules. A. unclu- 

 latus would thus include all those having 

 a vague or indefinite umbilicus, and A. 

 senarius those in which the umbilicus is 

 separated from the cellulose compart- 

 ments by a well-defined margin. 



A. spiendens (Shadbolt). — Compart- 

 ments (12 to 20) obscurely cellulose, 

 each with a median line, which termi- 

 nates in a clavate intramarginal nodule 

 or tooth ; umbilicus hyaline, definite. = 

 Actinophcenia spiendens, Sh TM. ii. p. 16 j 

 Actinojjti/chus sedenarius, E., Ro TM. ii. 



f). 74, pL 6. f. 2. Common. Guano, Eng- 

 and. In this species the alternate de- 

 pressions of the compartments are often 

 very slight ; and the compartments being 

 striated, frequently appear irregular, and 

 are coimted wdth difficulty. The species 

 nevertheless has so peculiar an aspect, 

 that, once kno"«Ti, it is easily recognized. 

 The rays are most distinct where they 

 radiate from the hyaline umbilicus, at 

 which part they sometimes appear thick- 

 ened. In some specimens the nodules 

 are confined to the alternate compai't- 

 ments. 



A. elegans (n. sp.). — Disk divided into 

 compartments by lines radiating fi'om a 

 stellate, hyaline umbilicus ; compart- 

 ments punctated, and each bisected by 

 a monilifonn row of granules. =A. octo- 

 detiarius, EM. pi. 21. f 21. Oran. Ehren- 

 berg has figm'ed more than one form as 

 his A. octodenanus ; the compartments in 

 his figure of this species are 9, and each 

 is bisected by a monilifonn ray. 



A. tnlingidatus(Bii.). — Valves divided 

 by 6 alternately elevated segments. I'he 

 elevated portions gTadually rise from the 

 circumference to near the centre, where 

 they are rounded oft'; each alternate one 

 has' a submarginal row of dots or trun- 

 cated processes. Sm-face delicately punc- 

 tato-sti-iate. -0035" to -0073". " West 

 Indies. Bri MJ. viii. p. 93, pi. 5. f. 2. 



A. sjnnosus (Bri.). — Valves with 6 seg- 

 ments, alternately slightly elevated; mar- 



gin occasionally spinous; each segment 

 Tvdth 1 or 2 processes ; mnbilicus smooth, 

 surface of the valve punctate. Monterey 

 , earth (or deposit). Bri MJ. viii. p. 94, 

 pi. (3. f. 15. 



A. dives (E.). — Disc divided into 

 numerous (about 50) narrow compart- 

 ments by lines radiating from a large, 

 indefinite, punctated umbilicus, each 

 compartment having a single series of 

 granules. EM. pi. 19. f. 12. =Discoj)lea 

 dives, E. ; Cyclotella dives, KA. p. 20. 

 Fossil. JEgina. 



Doubtful Species. 



A. qiiaternarius (E.). — Disc divided 

 into 4 compartments by as many radi- 

 ating lines. KA. p. 130. Virginia. 

 Diam. 1-552". A state of A. ternarius ? 



A. ? hexapterus (E.). — Disc \\ath 6, 

 thick, solid and conical rays ; margin 

 thick, undulated, denticulate internally. 

 KA.p.l31. Fossil. Vera Cruz. (xi. 31.) 

 A very doubtfid Diatom. 



A. octonarins (E.). — Disc divided into 

 8 compartments by as many radiating 

 lines. Guano, &c. A state of "^4. senarius. 



A. denarius (E.). — Disc with 10 com- 

 partments and 10 radiating lines. EM. 

 pi. 18. f. 23. Cuxhaven and Virginia. 

 We believe this species is foimded on 

 certain forms of A. senarius and A. 

 spiendens. 



A. duodenarius (E.). — Disc divided by 

 radiating lines into 12 compartments, 

 which are alternately darker ; in the 

 centre of each compartment runs a nar- 

 row line, terminating at the margin in a 

 minute pseudo-nodule, so that as many 

 as 24 rays may be counted. Eecent and 

 Fossil. Europe, America. KA. p. 131. 

 = HeUopeUa Phaethon, MJ. viii. p. 13 ? 

 A state of A. sj^lendens ? 



The following species of Ehrenberg 

 are distinguished by the nimiber of rays 

 only : — 



A. quatuoj'defiarius, 14 rays=^. ^len- 

 dens; A. vicenarius, 20 ravs; A. Ceres, 

 22 rays ; A. Jupiter, 24 rays (xi. 28). 

 The three last are probably states of 

 A. splejulens. 



Genus HELIOPELTA (Ehr.). — Frustules disciform, undulated disc cellu- 

 lose, with external rays and internal septa, a striated margin, many erect 

 submarginal teeth, and an angular centre. As in Actinoptychus, the frustiile 

 is undulated, and the disc divided into cuneate compartments or rays, which 

 appear alternately more distinct ; " but, in addition, they have near the 

 margin a row of lateral spines, somewhat like the processes of Eupodiscus, 

 but far more numerous, which probably connect the frustiJes together in the 



