KONGL. SV. VET. AKAUBMJENS HANDLINGAR. BAND 26. N:0 2. 39 



Var. inflata Per. (1891). — V. lanceolate, sigmoid, acute. L. 0,32: B. 0,o4 mm. Transv. 

 and. obi. striae 'Yjg in 0,oi mm. — P. decorum var. infl. Per. p. 5 PI. I f. 10. 

 Marine: Corsica (Per.). 



18. P. kerguelense Grun. (1880). — V. linear, elongated, slightly sigmoid, with obtuse ends. 

 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 obi. striae ^7,3 in 0,oi mm. — Grun. A. D. p. 49. Per. II f. 1. 



Margine: Kerguelens Lan(^! 



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

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

 striae "-/13 (Grun.) 17,,, '7,5. — Grun. A. D. p. 49. Per. II f. 3. 



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



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

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

 nected with P. speciosum. 



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

 L. 0,104 to 0,13; B. 0,015 to 0,017 mm. Median line central, slightly sigmoid. Central nodule 

 elongated. Transv. and obi. striae ^^j^^, 2726' ^*/27' ^^28- — P- delicatulum var. salin. Grun. Casp. Sea 

 Alg. p. 116. P. sal. Grun. A. D. p. 54. Per. VI f. 16. 



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



Var. pusilla Grun. (1880). — L. 0,o74 to 0,094; B. 0,012 to 0,oi8 mm. Jransv. and obi. 

 striae 27^., ^s/^g. — 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. obi. striae 17201 ^^lii ^ 

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



Marine: Connecticut, Morris Creek (Per.). 



21. P. praelongum Cl. N. Sp. — V. linear, slender, slightly sigmoid, with obtuse ends. 

 L. 0,3 to 0,4; B. 0,03 to 0,033 mm. Median line central, slightly sigmoid. Transv. and obi. striae 

 ''72.3. '^At in 0,01 mm. — PI VI f. 2 (Part II PI. I f. 2). 



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



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

 well; M. J. VII p. 180 PI. IX £ 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 Brightwell. 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,o54 mm. Median line central. Transv. and obi. striae '72i' "/zu "^"/^u 

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



Marine: North Sea! Mediterranean Sea! Adriatic! Red Sea! Samoa! "West Indies! Colon! 

 Magellhaens Straits! 



Var. gigantea Grun. (1860). — More lanceolate, with obtuse ends. L. 0,44; B. 0,068 mm. 

 Median line very slightly undulating, central, frequently bordered by a row of small dots. Transv. 

 and obi. striae "/jg, "/20, "/20 in 0,oi mm. — P. giganteum Grun. Verb. 1860 p. 558 PL VI f. 1 

 A. D. p. 53. Per. VI f. 2. P. validum 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). 



