38 p. T. CLEVE, SYNOPSIS OF TLE NAVICULOID DIATOMS. 



slightly excentric towards the ends. Transv. and obi. stride 25 in 0,oi ram. — P. dclic. W. Sm. 

 Ann. Mag. Nat. H. [2J IX p. 6 PI. I f. 5. B. D. I p. 64 PI. XXI f. 202. Per. p» 13 PI. V f. 20 to 22. 



Brackish water: North Sea! Casi3ian Sea (GrRiTN.), Red Sea (Grun.)! Massachusetts! Hondu- 

 ras (Grun.). 



Var. ohtusiuscula GrRUN. Ms. — More obtu.se. L. 0, i 05; B. 0,01 it.^) mm. Sti-iw 22,5 in(t,()i mm. 



Marine: Granton Quarry (Grun.). 



Var. africana Grun. (1879). — L. 0, is to 0,19; B. 0,014 to (),oi8 mm. Transv. and obi. striae 

 2%, in 0,01 mm. — Grun. in Cl. M. D. N:o 197. 



Brackisli water: South Africa! 



Var. anwricana Cl. — L. 0,28; B. 0,02 mm. Transv. and obi. striie 19 in 0,oi mm. 



Brackish water: Qiaincy, Mass.! 



16. P. eloiigatum W. Sm. (1852). — V. slightly sigmoid, elongated, gradually attenuate to 

 the acute ends. L. 0,i3 to 0,38; B. 0,024 to 0,03 mm. Median line central, slightly sigmoid. 

 Tramsv. and obi. strife >»/,6, 17,8, 27, j, 20/^^^ -m.^^ j^ 0,01 mm. — W. Sm. Ann. M. Nat. H. [2] IX 

 p. 6 PI. I f. 4. B. D. I, PI. XX f. 199. Per. Ill f. 5 to 8. F. angulatum var. elongat. V. H. Syn. 

 p. 115 PI. XVIIT f. 7. P. dongatum var. grarili.^ Grun. Casp. Sea Alg. p. 115 PI. Ill f. 7. Per. 

 II f. 20, 21. 



Brackish water: Spitsbergen! North Sea! Atlantic coast of North America! Mediterra- 

 nean Sea! Adriatic! Java! Sumatra! China! Tahiti! Halle in Saxony! Baltic! Ca.spian Sea (Grun.) 

 Medoc (Per.). 



Var. gracilescens Grun. (1880). — V. very narrow, gently sigmoid, with acute ends. L. 0,204 ; 

 B. 0,0 16 mm. Median line central. Transv. and obi. strife '^'Vib.-. ^'^ ^'"i ™™- ~" P- ffi^f^cilescens 

 Grun. A. D. p. 50. Per. p. 7 PL III f. 9. 



Marine: Seychelles (Grun.). 



P. elongatum is very nearly akin to P. (lelicafuhim, but the transverse stricB are a little 

 closer than the oblique and it has a perfectly central median line. Still these characteristics 

 seem not to be constant, as I have forms of the shape of P. ddicatulnm with the striation of P. 

 elongatum (specimens from Java and Sumatra have the form of P. delicatulum and transv. obi. 



StricE 20/^^, 19/^^). 



Var. fallax Grun. (1880). — V. gently sigmoid, narrow linear or lanceolate. L. 0,i to 0,17; 

 B. 0,022 to 0,0 24 mm. Median line sigmoid, central. Transv. and obi. striai ^^20' '^'^/•n^ ^V-ii i" 

 0,01 mm. — Grun. A. D. p. 50 PI. Ill f. 66. Per. II f. 23. 



Marine: Finmark, Sea of Kara (Grun.), Sumatra (Deby coll.)! 



Specimens from Sumatra are much more narrow than the fig. in A. D. and resemble greatly 

 P. delicatulum, but have the median line perfectly central. 



Var. hariana Grun. (1880). — L. 0,2 to 0,21; B. 0,o2 to 0,022 mm. Median line perfectly 

 central. Transv. and obi. strise -Vi9» ^%o i'^ ^'Oi mm. — P. ddic. var.? kariana Grun. A. D. p. 50 

 PI. Ill f. 69. P. l-arianmn Per. p. 6. 



Marine: Sea of Kara (Grun.). 



This form connects P. elongatum with P. longum. 



17. P. longum Cl. (1873). — V. narrow, linear-lanceolate, slightly sigmoid, with acute 

 ends. L. 0,i8 to 0,3; B. 0,oi8 to 0,021 mm. Median line central. Transv. and obi. stria' ^"/u' 

 ''7i6> ^Vi7 in 0,01 mm. — Cl. D. of Arct. Sea p. 19 PL III f. 14. Grun. A. D. p. 49 PL III f. 71. 

 Per. II f. 2. 



Marine: Greenland! Spitzbergen! 



Var. atnericana Per. (1891). — V. narrow lanceolate, witli acute ends. L. (),3r) to 0,4; B. 

 0,02 to 0,02.') mm. Median line very slightly excentric at the ends. Transv. and obi. striye 'Vh 

 (Per.) '7i,-, ill O't" i"m. — P. deeormn var. americ. Per. p. 5 PL T f. 9. 



Marine: Connecticut! 



