OF THE ACTLNISCE^. 



935 



lanceolate; secondary tubes distinct. KB. 

 p. 118, pi. 27. f. 12. = Schizonema albicans, 

 Me. Adriatic Sea. 1-1200" to 1-1080". 

 Meneghiui describes the valves as broadly 

 elliptic. 



M. Berheleyi (K.).— Frond tufted, dull 



ojiye-brown ; filaments setaceous, rather 

 rigid, branched ; branches erect, attenu- 

 ated ; naviculse large; valves eUiptic- 

 oblong, in very distmct secondary tubes. 

 KA. p. 106. Torquay. NavicuL-B in 

 front \dew paraUelogramic. 1-1080". 



FAMILY XIX.— ACTimSCE^. 



Individuals silicious, furnished with radiating spines. Marine. The Acti- 

 nisceae bear little or no resemblance to the Diatomaceae, and ought to be ex- 

 cluded from them. M. de Brebisson thinks they would be more appropriately 

 placed near the Arceila, EugljT3ha, or some allied genus. On the other hand, 

 Professor Bailey would refer them to the Polycystina. 



Genus ACTINISCUS (Ehr.).— Frustules solid, star-like. Actiniscus differs 

 from Dictyocha and Mesocena in having a solid centre or body from which 

 rays, varying in number and form, diverge. 



Actiniscus Sirius (E.). — Rays 6, 

 acute, winged at the base. EM. pi. 33. 

 lo. f. 1. l-lloO". Alive, Norway ; fossil, 

 America. The rays seem to arise from 

 the disc, and not from the margin. 



A. Pentasterias (E.). — Rays 5, acute, 

 not (or but partially) exserted. EM. 

 pi. 35 a. 23. f. 1. 1-1150". Alive, 

 Norway ; fossil, Greece and America. 



A. Tetrasterias (E.). — Rays 4, acute, 

 not (or but partially) exserted. EM. 

 pi. 18. f. 62. 1-1008". Virginia. The 

 last two forms may be varieties of A. 

 Sinus. 



A. ? Stella (E.). — SteUate, with 6, 

 marginal, obtuse rays or teeth. = Dicty- 



ocha, E. 1838. Fossil. Eui'ope and 

 Africa, 



A. ? quinarius (E.). — Stellate, with 5, 

 marginal, obtuse rays or teeth. 1-3120". 

 Fossil, ^gina. 



A. ? Rota (E.).— Wheel-Hke, with 10, 

 short, obtuse, spoke-like rays. 1-1920". 

 Oran. 



A. ? Discus (E.). — Disciform ; centre 

 smooth ; rays 8, marginal, not exserted. 

 1-2304". Oran. According to Ehren- 

 berg, the last four species may belong to 

 Phytolitharia. 



A. ? Lancearius (E.). — Stellate, with 

 8 exserted, lanceolate rays, and some 

 central shorter ones. 1-240". 



Genus DICTYOCHA (Ehr.). — Frustules free, spinous, reticulately per- 



forated ; foramina large. 



* Foramina, or cells, two or three. 



Dictyocha Ponticulus (E.). — Frus- 

 tules oblong, unarmed, transversely 

 divided into 2 cells. 1-432". Fossil. 

 Bermuda. 



D. Quaclratum (E.). — Subquadrate or 

 oblong, transversely divided into 2 cells, 

 a spine at each end. 1-480". Bemiuda. 

 These two forms were first obsei-ved and 

 figured by Professor Bailey. 



D. Pons (E.). — Roimdish, ^dth 2 cells 

 and 4 spines. 1-504". Oran. 



D. triacantha (E.). — Triangular, with 

 spinous angles ; cells 3. unarmed. Mary- 

 land. 



D. tri^iyla (E.). — Roundish, with 4 

 irregular spines; cells 3, unarmed. 

 1-492". Oran. 



D. trifenestra (E.). — Quadi-ate, 4- 

 spined; cells 3, dentate. Recent and 

 fossil, (xv. 35.) 



D. Ahijssarum (E.). — Frustides trian- 

 gular, with 2 cells ; spines 3 ; 1 ceU fm*- 

 nished with an internal tooth. EB. 

 1854, p. 238. Atlantic. 



2* Diamond-shaped or quadrate ; 4- 

 spined; foramina 4 or more. 



D. P'ihula (E.). — Cells 4, unanned. 

 1-1150" to 1-560". Recent and fossil. 

 (XV. 34.) 



D. Epiodon (E.). — Resembles D. 

 Fibula, but the cells are fimaished with 

 a tooth. Recent and fossil. 



D. abnormis (E.). — Cells 5, unequal, 

 all marginal. 1-1080". Fossil. 



D. Crux (E.). — Four unanned cells 

 round a central one. 1-624". Fossil. 



D. Staurodon (E.). — Resembles D. 

 Crux; but each marginal cell bears a 

 tooth. 1-576". Fossil. Virginia. 



D. mesophthalma (E.). — Resembles 

 the two preceding species ; but each mar- 



