KONGL. SV. VKT. AKADEMIENS IIANJ)LINGA1{. RAN]) 26. N:() 2, 89 



Var. inflata Per. (1801). — V. lanceolate, sigmoid, acute. L. 0,:52: B. 0,o4 mm. Transv. 

 and. obi. striiv- 'Vis ^^ 0'"' ^^^^- — ^^- 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 mui. Median line central, slightly sigmoid. Ends of the valve 

 with a lunate marking. Transv. and obi. stritii 'Vis ^^ 0,oi mm. — Grun. A. D. p. 49. Per. 11 f. 1. 



Margine: Kerguelens Land! 



19. P. Sllbrigidiiiil 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. 

 strise '"'^/is (Grun.) i9/,j, 17,5. — Grun. A. D. p. 49. Per. II f. 3. 



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



All the above species from P. Clcvci to P. suhrigidnm form a closely connected series. 

 F. suhrif/idum is, by its striation and the excentricity of the median line towards the ends, con- 

 nected with F. speciosum. 



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

 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 obi. strise ^-j^^, ^-^/og, '^*,-2v "Vas- — ^- (^elicatulum var. salin. Grun. Casp. Sea 

 Alg. p. 116. P. sal. Grun. A. D. p. *54. Per. VI f.'lG. 



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 obi. 

 striae ^s/^., ^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. O.017 mm. Transv. and. obi. stria? '*/2o» *"/2i i^ 

 0,01 mm. - P. 2)arad. Per. p. 16 PI. VI f, 13. 



Marine: Connecticut, Morris Creek (Per.). 



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

 L. 0,3 to 0,4; B. 0,03 to 0,03.-) mm. Median line central, slightly sigmoid. Transv. and obi. stride 

 20/2,, 21/24 in 0,01 mm. — 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 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 Brightavell. Peragallo believes that P. Longine may be a form of P. robusfiim, 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. Transv. and obi. striae '%,, '"/j,, ^o/^,, 

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



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

 Magellhaens Straits! 



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

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

 and obi. strite '7,^, "/20' 'V'.o in 0»oi mm. — P. giganteum Grun. Verb. 1860 p. 558 PI. VI f. 1 

 A. I), p. 53. Per. VI f. 2. P. validnm 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). 



