KONGL. SV. VKT. AKADEMIENS HANDLINGAK. BAND 26. N:0 2. 39 



Var. infläta Per. (1891). — V. lanceolate, sigmoid, acute. L. 0,32: B. 0, 04 mm. Transv. 

 and. obl. striiB 'Vis i^^ 0,oi mm. — F. decorum var. infl. Per. p. 5 Pl. I f. 10. 

 Marine: Corsica (Per.). 



18. P. kerguelense G-run. (1880). — V. linear, elongated, sHghtly sigmoid, with obtnse eiids. 

 L. 0,27 to 0,38; B. 0,023 to 0,026 mm. Median line central, slightly sigmoid. Ends of the valve 

 with a lunate marking. Transv. and obl. striti; '7i3 ^^ 0,oi mm. — Grun. A. D. p. 49. Per. II f. 1. 



Margine: Kerguelens Land! 



19. P. snbrigiduni Grun. (1880). — V. linear, gently sigmoid, with obtnse ends. L. 0,29 

 to 0,32; B. 0,028 to 0,03 mm. Median line central, slightly sigmoid at the ends. Transv. and obl. 

 striee ".^/j^ (Grun.) "/,j, J«/,j. — Grun. A. D. p. 49. Per. II f. 3. 



Marine: North Sea! Mediterranean Sea! Sumatra (Deby coU.)! 



All the above .species from P. Clevei to P. suhrigiämn form a closely connected series. 

 P. suhrigiämn is, by its striation and the excentricity of the median line towards the ends, con- 

 nected with P. speciosum. 



20. P. salinarum Grun. (1878). — V. linear to narrow lanceolate, slightly sigmoid, obtnse. 

 L. 0,104 to 0,13; B. 0,0 15 to 0,0 17 mm. Median line central, slightly sigmoid. Central nodule 

 elongated. Transv. and obl. strige --/o,,, ^^jg, -V271 'V28- — ^- äelicafulum var. salin. Grun. Casp. Sea 

 Alg. p. 116. P. sal. Grun. A. D. p. 54. Per. VI f."l6. 



Brackish water: Sweden, Lysekil! Kissingen (Grun.), Caspian Sea (Grun.), Bengal! Sumatra! 



Var. pusilla Grun. (1880). — L. 0,074 to 0,094; B. 0,012 to 0,oi8 mm. Transv. and obl. 

 strice 23/^., 23^_^^_ — p pusillum Grun. A. D. p. 54. Per. VI, f. 15. 



Fresh water: Bengal (Grun.). 



Var. paradoxa Per. (1891). — L. 0,044; B. 0,oi7 mm. Transv. and. obl. strise 17201 "/21 "i 

 0,01 mm. - P. parad. Per. p. 16 Pl. VI f, 13. 



Marine: Connecticut, Morris Creek (Per.). 



21. P. prselonguin Cl. N. Sp. — V. linear, slender, slightly sigmoid. with obtnse ends. 

 L. 0,3 to 0,4; B. 0,03 to 0,035 mm. Median line central, slightly sigmoid. Transv. and obl. strise 

 20/23, "/24 in 0,01 mm. — Part II Pl. I f. 2. 



Marine: Greenland! Spitsbergen! Finmark! Sea of Kära! Elephanta, Bombay (Grove coll.)! 



This large form, widely distributed in the Arctic Seas, niay be P. Longine W. Sm. (Bright- 

 well; M. J. VII p. 180 Pl. IX f. 7, 1859. Per. VIII f. 3) from the arctic regions. At least the 

 outline and the median line are exactly similar. I know of no arctic form agreeing with the de- 

 scription of Brightwbll. Peragallo believes that P. Longine may be a form of P. robustum, but 

 the latter species occurs only in warmer seas and has an excentric median line. 



22. P. rigidum W. Sm. (1853). — V. linear lanceolate, almost straight, with truncate ends. 

 L. 0,3 to 0,36; B. 0,04 to 0, 054 mm. Median line central. Ti^ansv. and obl. striee ^%j, "/2j, -"/■>], 

 in 0,01 mm. — W. Sm. B. D. I p. 64 Pl. XX f. 198. V. H. Syn. Pl. XIX f. 3. Per.'v1 f. 4 to 6. 



Marine: North Sea! Mediterranean Sea! Adriatic! Hed Sea! Samoa! West Indies! Colon! 

 Magellhaéns Straits! 



Var. gigantea Grun. (1860). — More lanceolate, with obtnse ends. L. 0,44; B. 0,o68 mm. 

 Median line very slightly nndulating, central, freqnently bordered by a row of small döts. Transv. 

 and obl. strife 'Vis' ''Ac ''Ao ^^ OjOI "^m. — P. giganteum Grun. Verh. 1860 p. 558 Pl. VI f. 1 

 A. D. p. 53. Per. VI f." 2. P. validmn Shadb. T. M. S. II p. 16 Pl. I f . 8 (1854)? 



Marine: Java! Philippines! Samoa! 



Var. incurva Brun. (1891). — V. strongly sigmoid. — Per. p. 15 Pl. VI f. 7. . 



Marine: Japan, fossil (Brun). 



